The submitted data is inconsistent across projects and comparison results include an unknown margin of error. This should not discount the reductions each project made, though it does introduce outliers when attempting to compare and rank. Please note the following:

• Submitted projects span the range of development stages, resulting in varying material quantity accuracy and the depth of individual building components included.
• Interior data was included in results data on projects that submitted it.
• Biogenic Carbon was not consistently reported, included, or discluded from the results. This resulted in one greatly exaggerated reduction outcome and disadvantaged other timber structures who do not have the value included in their result calculations.

The Whole Building Life Cycle Assessments from the projects needed to include the following scope at a minimum:

• Life cycle stages A1-A3, A4, B4, C1-C4. Additional physical scopes or phases of life may be submitted, but are not required.
• Physical Scope: Substructure, Superstructure, Exterior Enclosure
• Environmental Indicators: Global Warming Potential (GWP)
• The baseline and proposed buildings must be of comparable size, function, orientation, and operating energy. The service life must be the same and at least 60 years.
• Use the same assessment software tools and data sets to evaluate both the baseline building and the proposed building. Data sets must be compliant with ISO 14044.

Owner: Trustees of the Jones Library
Architect: Finegold Alexander Architects
Structural Engineer: RSE Associates

Project Overview:
The Jones Library in Amherst, MA was founded nearly a century ago. The collection’s permanent home was constructed in 1928; a residential-style building with stone walls, a gambrel slate roof, and an elaborately carved entablature. The interior has ornately detailed window and door surrounds, arched transoms and hand-carved stairs. An addition was added in the 1990s but is slated for demolition in the current renovation design. It will be replaced with a new 42,000 SF addition to meet the needs of a modern library. The project also includes the restoration and reuse of the structure, the envelope, and much of the interior woodwork of the historic 1920s building.

Sustainability has been a priority for the owner and project team since early design. The proposed project eliminates fossil fuels and will be all-electric and solar ready. The team had early conversations about reducing embodied carbon as well. The first strategy was to build less. The reuse of the historic structure and interior components contributed to this goal by capitalizing on the carbon already emitted in their construction. The addition was then designed to be highly efficient, flexible, and compact to limit the area needed in the new footprint. It is the smallest allowable size per the Massachusetts Board of Library Commissioners.

The next sustainability tactic was to build low carbon. The structure of the addition was designed for a hybrid mass timber and steel frame with CLT floor slabs. This was the most significant way to slash embodied carbon. Concrete foundations and footings were proposed with 30-35% fly ash for carbon reduction. Interior finishes were selected with long-term durability and cleanability to extend their useful life and avoid quick replacement in the future.

Replicability:
According to some estimates, there are over 300 billion square feet of existing buildings in the US. To best decarbonize the built environment, these existing structures should be utilized and renovated for greater energy efficiency. The Jones Library is an example of both reuse and new construction to reduce carbon emissions. The existing structure and envelope reuse account for roughly 30% of the completed project. Adding new square footage to it allows for better preservation of the old. The library addition solves accessibility issues with a new elevator and ramped access to two side wings in the original building that would otherwise not be accessible. The existing floor-to-floor heights are very low and inadequate for new mass timber beams and mechanical distribution. The new floors had to be taller than the original with ramps designed for smooth transitions. With the new addition carving out the space for accessibility and mechanical systems, it allows more of the history of the original portion to be preserved.

This project is also an example of incorporating a hybrid timber structure into a building typology with a high demand for quiet. Despite all the other benefits of timber and CLT, the inherent acoustics are simply not adequate for a library’s sound and impact isolation needs. The design team balanced the sustainability goals with the acoustic requirements and proposed a floor system consisting of a 6.75” CLT floor deck covered by 1.25” thick resilient mat and a 2” layer of gypcrete. This increases the mass and absorption of the floor system to raise STC levels without adding significant embodied carbon. Gypcrete is a lightweight concrete mix with a proposed 15% fly ash to further reduce the carbon impact.

Cost Effectiveness:
Building reuse and preserving historic components have value beyond just a dollar amount but, in this case, reuse also contributes to reduced construction cost since fewer new materials must be purchased. Based on our TallyLCA estimates, the proposed project prevents nearly 200,000 kg of mass from going to a landfill through reuse efforts. Much of that mass is the structure and envelope which are also high-cost items. Millwork reuse has fewer cost advantages, but duplicating the historic carvings would be costly. Instead, reuse preserves a unique creation and avoids extra embodied carbon.

As cost estimates have been completed in the various design stages, cost reduction efforts have been necessary. Even with a slight cost premium for the mass timber structural system, the owner has been adamant that it remains, and scope be removed elsewhere. Sustainability was never on the table for value engineering. The use of a wood structure does help reduce the cost of finishes that would otherwise be needed to cover a steel or concrete structure. The wood provides an inherently beautiful finish.

The roof was redesigned to lower both cost and embodied carbon. The initial sawtooth roof over the addition provided amble daylight to the core reading rooms, but was also expensive and utilized significant glass, metal framing, and roof flashing. Skylights are discouraged in libraries, so the team revised the design with a single roof pop up with windows on all sides. This building lantern allows natural daylight to brighten the inner spaces with less material and cost than the sawtooth roofline.

Innovativeness:
Some of the best innovations are a simplification from an otherwise cluttered process. There are three simple ways that the approaches in the Jones Library project are unique and innovative.

The design team’s greatest strategy to reduce embodied carbon was in having open discussions about carbon with the owners from the very beginning of design. Changing structure and materials is much harder later in the process. These early conversations embedded the sustainability goals into the design so they could be preserved through design and into construction later this year.

The natural beauty of wood in the timber structure and CLT floors are a key part of the design material palette in Jones Library. The floors required an acoustic topping to mitigate noise, eliminating the possibility of exposing them as finish floors. In spaces below the CLT slab the team found ways to achieve noise control while exposing the beauty of the wood structure. Rather than using acoustic ceiling tiles, a series of suspended acoustic fins were designed to absorb sound without obscuring views of the wood. Wood columns and beams were left exposed where possible.

Lastly, designing for flexibility is a “future-proofing” strategy to help avoid frequent renovations, and their associated carbon, down the road. The team found that adding extra storage (beyond what is typically included) in and near key spaces allows for greater flexibility. Greater storage allows the furniture to shift in and out as program changes within the same space. This flexibility and flex space also helped to reduce the overall square footage needed in the building, further reducing embodied carbon from what could have been a much larger building.

Client: University of Massachusetts Amherst & UMBA
Architect: Payette
Structural Engineer: LERA Consulting Structural Engineers
Contractor: Suffolk

Project Overview:
With the new 74,000 GSF Sustainable Engineering Laboratories (SEL), UMass Amherst is building a national hub to accelerate clean energy research and educate tomorrow’s sustainable engineering workforce. This cutting-edge living laboratory is designed to catalyze bold discoveries that can be replicated and scaled to deliver real-world solutions, with research concentrations in batteries, energy, transportation, and environmental technology. The SEL features flexible interdisciplinary workshops, shared specialty labs, instructional classroom spaces and a welcoming student learning commons. The flexible nature of the lab spaces future-proofs the building against obsolescence tied to the rapidly changing nature of academic research.

Total carbon reduction was a key project goal from the outset. Embodied carbon was studied in parallel with operational energy and other sustainability strategies, with anticipated certifications for LEED Platinum and ILFI Zero Carbon. The design team used early-phase, iterative analyses to compare options for the building structure, envelope and layout that informed key carbon reduction strategies. The mechanical systems were relocated from the basement to ground level and roof to reduce excavation costs and carbon-intensive foundation work. The structural grids were also optimized to reduce materials, also saving a significant amount of carbon.

Net program area is maximized relative to gross area and building volume via compact, efficient planning and a ‘skip stop’ sectional strategy that introduces three floors of offices (lower height requirements) into two floors of labs (taller requirements), thereby enclosing more program with less facade area and less structure.
Low-carbon materials and assemblies were prioritized throughout the project. In addition to the hybrid steel-timber structure, the concrete mixes were optimized to replace nearly 50% of the cement with low-carbon alternates. Other strategies included using polyisocyanurate roof insulation, timber curtainwalls and wood-framed windows throughout most of the building.

Replicability:
When designing the carbon reduction strategies for SEL, it was important to make sure that the strategies could be easily replicated. Basic, first-principles approaches to space planning yielded significant savings without relying on unique or proprietary systems or materials. Carbon intensive below-grade construction was minimized by moving mechanical and electrical services to the ground floor and rooftop. Reduction in gross area and façade area, while maintaining net program, delivered the same functionality with less building – another win for both cost and carbon (not reflected in the LCA due to ISO requirements for matching areas). Rigorous optimization of the structural grid to reduce column and beam quantities cut the total steel used in the building by over 20%. As a publicly-bid state project, SEL is required to use open specifications, ensuring that the majority of materials used in the project are widely available from multiple suppliers. This also suggests that the materials will be available for future projects.

The team was also careful to suggest material substitutions that were cost neutral. For example, specifying polyisocyanurate instead of XPS for the roof assembly yielded the most dramatic carbon savings of any one variable in the LCA comparison. This simple change to a specification section did not incur additional costs, loss of performance or aesthetic compromise.

SEL incorporates mass timber construction in a program type traditionally averse to this. The use of mass timber in lieu of steel and concrete structural systems has well-demonstrated benefits of reduced embodied carbon. However, laboratories have been much slower to adopt this innovation compared to other program typologies (such as office buildings) because the strenuous vibration criteria can make mass timber prohibitively expensive. The hybrid steel-timber system used for the SEL project offers a unique middle-ground: the carbon benefit of mass timber decking is integrated with the stiffness of steel framing.

Cost Effectiveness:
SEL is a state-funded project with a strict budget. Throughout the design phases, the cost and carbon analyses were completed in parallel. By comparing project budget estimates against early LCA studies, we developed a “cost per carbon reduction” method: a dollar value for every ton of carbon avoided or reduced through design. This method informed three key approaches to cost effectiveness.

First, we looked for optimizations to reduce both cost and carbon at the same time. This included minimizing below-grade construction, reductions in gross area and reductions in steel tonnage through structural grid optimization. These strategies cut nearly 5% out of the estimated construction cost, translating to $4 million in savings that were reallocated to other project priorities.

Next, we fine-tuned our specifications to include “low-premium” items that delivered carbon savings without impacting the budget. This included polyisocyanurate for the roof insulation and increased SCMs for the concrete mix design.

We recognized that some strategies, such as mass timber decks and timber curtainwall, may have initial large cost premiums. Therefore, we used an integrated systems approach to demonstrate the value of both strategies. The structural premium for timber was much lower when considering the added price of ceiling assemblies of similar acoustic and aesthetic quality that would be needed with a metal deck. The timber structural deck was about $50/sf more expensive than metal deck when looking at structure only, but a ceiling could add $25-85/sf. The timber decks also required fewer steel beams.

For the timber curtainwalls, we used Payette’s Glazing and Winter Comfort Tool to analyze the thermal performance of timber vs. aluminum mullions with the goal of improving thermal comfort for the building’s occupants. This eliminated the need for perimeter heating, which resulted in significant mechanical cost savings, which helped offset the increased façade costs.

Innovativeness:
The SEL design team used a variety of tools and iterative analysis to reduce embodied carbon throughout the project. Kaleidoscope, Payette’s embodied carbon tool, compares multiple envelope and interior assemblies to inform the selection of materials and façade systems. EPIC provided a coarse-grained analysis of operational and embodied carbon, predicting the total footprint of LCA scopes before the design was detailed enough to perform a Whole Building LCA using Revit plug-ins. Tally and EC3 were also consulted early in SD to compare design options.

LERA developed a matrix of 64 structural systems with steel, concrete, mass timber and hybrid assemblies. They were reviewed for embodied carbon, cost, depth, aesthetics and vibration. Ultimately, a hybrid steel and timber system was selected to meet the vibration requirements of the labs while delivering a significant carbon reduction against steel and concrete systems.

This iterative structural process also led to the steel beams being embedded into the depth of the composite timber deck, reducing overall structural depth while allowing a reduced floor-to-floor height. This reduced the total façade and interior wall area – saving both cost and embodied carbon.

Acoustical performance was analyzed throughout the process. Mass timber systems are generally criticized for their acoustic performance – partly because the sound-absorbing acoustic ceilings are often removed to display the beautiful timber decking. To mitigate this, SEL uses dowel-laminated timber (DLT) instead of the more common cross-laminated timber (CLT). DLT can be routed with grooves that accept acoustic foam – delivering a Noise Reduction Coefficient (NRC) of 0.70 from the structure itself. This acoustic DLT – despite having a slight material cost premium over CLT – delivered cost, carbon and aesthetic benefits. Without the need for acoustic ceilings or equivalent acoustic wall treatments, the construction fit-out schedule was accelerated, and more timber remains visible without compromise of the acoustic quality.

Owner: 2Life Communities;
Architect: Prellwitz Chilinski Associates, Inc.;
Civil/Landscape: Stantec;
Structural: B+AC;
MEP: Petersen Engineering;
Specifier: Kalin Associates, Inc.;
Contractor: Dellbrook | JKS

Project Overview:
PCA joined the Embodied Carbon Reduction Challenge to kick-start our efforts in understanding, measuring, and reducing embodied carbon. Leland House was our first test case.

PCA was privileged to team up with 2Life Communities and partners to design Leland House, an affordable senior living community. Designed to Passive House standards, Leland House brings improved health, economic, and environmental benefits to its residents and addresses the important objective of minimizing its carbon footprint.

Reducing embodied carbon was a primary goal of the project. However, without access to industry tools and resources, the team relied on estimations and intuition early in the design process. Since joining the Challenge, we’ve been able to measure the value of the project’s carbon reduction measures and educate the team on the carbon impacts of decisions made through construction.

Our carbon reduction strategies included low-carbon structural design solutions such as: mass timber columns and beams, wood-framed load-bearing walls, and wood trusses. Improved concrete mix designs included SCMs to reduce embodied carbon. Cellulose cavity insulation was used as a sustainable alternative to fiberglass insulation.

Additional project goals included specifying PVC free and Red List free interior finishes, while providing the community with an enhanced connection to nature through biophilic patterns, textures, and materials. Bio-based polyurethane resilient flooring provided an alternative to pervasive luxury vinyl tile. Low-carbon, alternative carpet tiles, plant-based acoustic ceiling tiles, wood veneer ceiling finishes, and exposed timber columns and beams contributed to the holistic design approach of the project.

Overall, Leland House demonstrated an 18% reduction in embodied carbon over baseline, including a: 15% reduction in the structure, 15% reduction in the enclosure, and 25% reduction in the interiors.

We found that Whole Building Life Cycle Assessment (WBLCA) provides us with the knowledge and data to reduce embodied carbon and help combat climate change.

Replicability:
Through the Challenge, we’ve gained access to the tools and training to perform life cycle assessments across various systems and scales. This in turn affords us the knowledge and data to impact design decisions on real-world projects.

Replicability was built into our process from the start. Upon joining the Challenge, one of PCA’s goals was to establish a workflow, understanding, and database that we could apply to the next project, so we could hit the ground running and target greater carbon savings. To this end, we created a Lesson Learned 2.0 Model to track carbon reduction measures that we might apply to the next project.

Selecting an affordable housing project, such as Leland House, was intentional, as it targets a highly replicable case study. The technologies we employed are common and well understood by the building industry at various scales and applications; wood-framed load-bearing walls and wood trusses provide cost-effective, low-carbon solutions to meet our most basic needs.

Concrete is a material we see on every project, and it was the largest contributor to embodied carbon emissions at Leland House. Here we learned a valuable lesson around providing performance-based specifications. Our specification allowed for up to 50% SCMs, but without specifying any minimum performance values, we wound up leaving another 35 metric tons of carbon on the table that could have been further reduced. We included these savings in our Lessons Learned 2.0 Model to demonstrate how to do better on the next project.

All the measures included in our proposed model successfully survived the VE process and are currently being constructed, further evidence of the replicability and cost-effectiveness of the strategies employed at Leland House. Design is inherently an iterative process, and the lessons we learned in our first WBLCA will form the foundation for the next project.

Cost Effectiveness:
LCA tools provide us with the knowledge and data to reduce embodied carbon and help combat climate change. The more we, as designers, request manufacturers’ EPDs and demand low-carbon alternatives for the most impactful materials, the more the costs will come down. In many cases, there are cost-effective, low-carbon solutions available to the marketplace.

WBLCA allows us to identify our most significant embodied carbon contributors (e.g., concrete, flooring products, steel, foam insulations, etc.) and focus our resources on targeting their reductions.

Furthermore, by taking a holistic design approach, we can identify synergies among project goals, such as eliminating PVC from the interiors and providing biophilic designs, while also reducing embodied carbon, all with a cost-competitive product. At Leland House, we used a bio-based polyurethane resilient flooring that provided a 42% reduction in carbon over ubiquitous LVT flooring. Resilient flooring was our second-highest contributor to embodied carbon. When high-impact design decisions can satisfy multiple project goals, they are more likely to remain part of the project, and LCA allows us to bring the carbon data to the table. Carbon tools and data help to illuminate these solutions.

Red List free composite alternative carpet tiles were priced competitively and saved the project 50% of the carbon of traditional carpet tiles. Similarly, plant-based ceiling tiles provided 1/3rd of the carbon of the typical ACT without an uptick in cost.

Gypsum board and paint were two of the larger contributing materials that we were unable to address in our study. In the case of gypsum board, our base spec already includes a low-carbon gypsum product and in the case of paint we were unable to find reliable data to give us the confidence to reduce. Further work is required in these categories and others to help steer the industry to lower carbon solutions.

Innovativeness:
Low-Carbon Affordable Housing 2.0 – Lesson Learned for the Next Project
Since we started the Challenge, we were mindful to track decisions we might have made differently had we had the benefit of quantifying carbon earlier in the design process. In addition to our Baseline and Proposed WBLCA models, we created a Lessons Learned 2.0 Model to track and quantify how we could improve our embodied carbon emissions on our next project. We reduced the embodied carbon in our Lesson Learned 2.0 by an additional 10%, or 28% total reduction over Baseline.

Early in design, we targeted an insulated foam glass aggregate for the under-slab insulation. At the time, we didn’t have the data to demonstrate the value of this approach. Had we known that XPS under-slab insulation was such a significant carbon contributor, we could have fought harder to keep the alternative insulated aggregate product and made a larger impact on our bottom line.

Additional strategies for deeper savings in our 2.0 Model included:
• Further improvement to the concrete mix design saved 27% over Baseline
• Low-carbon cementitious flooring underlayment saved 35%
• Mineral Wool Board insulation saved 22t CO2e, or 65% over Polyisocyanurate
• Balloon-framed parapets saved 1,700 kg CO2e
Total Carbon: Operational + Embodied Carbon
Leland House elected to use triple-pane, uPVC windows for improved occupant comfort and operational energy efficiency. We studied the total carbon impact of double vs. triple-pane windows. Based on today’s utility mix and assumption of a 35%, or 20t CO2e, increase in embodied carbon, we estimated the annual energy savings of 1.45% would lead to a “carbon payback period” of 2 to 5 years for triple-pane windows over double-panes. We believe this analysis can contribute to a larger discussion around tradeoffs between operational and embodied carbon. We present this innovative study for further discussion…

The Drucker Company (Client) / Beacon Capital Partners (Client) / Elkus Manfredi Architects (Architect)/Haley&Aldrich, Inc (Geotechnical Engineer) / Mikyoung Kim Design, LLC (Landscape Architect) / Nitsch Engineering (Civil Engineering) / McNamara Salvia Inc. (Structural engineer) / Jensen Hughes (Code Consultant) / Simpson Gumpertz&Heger (waterproofing/roofing ) /BR+A (MEP)/ Van Deusen & Associates (Elevator Consultant) / The Green Engineer (LEED consultant) / Sladen Feinstein Integrated Lighting (lighting consultant) / Acentech (acoustical consultant)

Project Overview:
Located in Boston’s South End neighborhood, 80 East Berkeley is a 10-story mixed use building with approximately 318,000 square feet of life science space coupled with approximately 13,000 square feet of ground floor retail spaces. The steel structure sits over two levels of underground parking for a total project area of 414, 647 square feet. The project has been designed to target carbon neutrality for operational carbon and is our firm’s first all-electric lab/office building. It shows a 36% site energy savings and 40% GHG emissions reduction against the Stretch Energy Code Baseline.

Construction is currently pending after completion of construction documents, which became an opportune moment for the embodied carbon reduction studies where opportunities for potential reductions were analyzed and recommendations were made following the studies.
This is the first holistic embodied carbon study done in the office.

Since the project is in construction documents we were not able to analyze the structural efficiency or make changes to the overall design of the building. While the design was optimized to reduce the window to wall ratio and include planted green terraces, those impacts have not been calculated. What we are able to impact are edits to the project specifications for specific product recommendations. Our goal was to find the impactful product categories that had EPDs and make selections based on the specific product requirements and that would not increase the project cost or require other changes.

The first change we made was to call for all concrete specifications to be performance specifications with a goal of less than the Eastern regional average baseline specified in the 2023 Carbon Leadership Forum Guidelines. This change was reflected in Tally. Further reductions were made per product, such as gypsum wall board, concrete masonry units, insulation, and roofing.

Replicability:
The reduction strategies were centered on conducting Life Cycle Analysis studies and identifying key contributors of high carbon. After conducting LCA studies with the baseline project, multiple discussions with the internal QAQC team members took place. This led to discovering opportunities to make low carbon substitutions that would offer the same performance but from manufacturers who have worked on reducing their products impacts. Also, learning from previous projects and bringing division-specific questions such as concrete mix designs to partnering consultants was helpful. Learning from experts inside and outside the firm led to the next step, which was to search for low-emitting products within the same category. This search was conducted by exporting data from Tally and importing to the EC3 tool. The team was able to find alternate products and identify significant reductions.

The data gathered from this process led to building firm-wide knowledge and created replicable strategies by making updates to our specification templates that we use on all of our projects. Most projects at Elkus Manfredi Architects share a similar base specification template and project-specific modifications are made on a case-by-case basis. The discovery of low-emitting products through LCA studies and comparing EPDs will lead to impact at least 29 projects that are currently scheduled to be constructed starting from 2024. These projects will have an average of 1,886,745 kgCO2e reductions, resulting to a reduction equivalent to the carbon sequestered in 71,456 acres of forests each year. This is comparable to the area that is 32 times larger than Middlesex Fells, or 1.2 times larger than the area of Boston.

Cost Effectiveness:
Emission reduction strategies for 80 East Berkeley is cost effective both in terms of design process and implementation. The extensive process of identifying key contributors and substituting with low carbon assemblies and then following with a search on manufacturers does not need to be repeated multiple times since the results will be reflected on the updated firm-wide specifications.

This approach of the reduction strategies from a material-based perspective is cost effective because it saves time. Time, as in billable hours, is money! The key to a successful reduction strategy lies in the convenience of executing sustainable decisions over the previously conventional ones. The proposed update on the specifications will allow designers and partnering engineers to easily make sustainable choices since it will not require many alterations in the design nor trigger additional coordination resulting from the change. The selected material alternatives that were proposed as part of the study are typically used in most of our projects. Suggesting specific materials and including a performance criteria regarding embodied carbon will also narrow down the search process of manufactures, which again saves more time.

Design decisions made in 80 East Berkeley demonstrates cost effectiveness as the alternate products that were selected are readily available and common in the marketplace from large manufacturers. The process of acquiring these materials is anticipated to be smooth without having issues with the supply chain or quantity. The products are not expected to be purchased at a premium, and if there is a premium it would be insignificant per our experience of using them on current projects.

Innovativeness:
This is the first holistic embodied carbon study done in the office. While it was not part of our project scope, we invested time in the research and exploration while capitalizing on the opportunity of the project being on pause. We were able to leverage the competition to dig into the details more holistically and address our typical construction materials. First we took a look at just the move to require a performance spec for concrete and that optimization along with key selection of insulation types such as mineral wool board and xps vs poly iso gave us a 12% reduction for the project. With approximately 29 projects of a similar or larger scale on the boards for 2024, this is a huge impact quantified on our board.

We then leveraged what we learned from the courses and participating in the LCA Forums to then export our tally results to EC3 and then identify specific products that could be easily substituted without a change to our designs. The idea being, we could create a new list of basis of design standard products in our template specifications which would affect all of our projects. This exercise that we did on one project, then was scalable to all of our projects.

One of the materials that are proposed in the optimized LCA model is concrete masonry units with Carbon X technology. This is a breakthrough technology that increases the reactivity of raw materials, which in turn reduces embodied carbon by reducing cement content in the blocks and increasing carbon sequestration. This allows each block to demonstrate significant amounts of sequestration from cradle to gate even before it is delivered to the site. Jandris has been a leader in their field and if it makes sense for our projects, including their product in our specifications supports companies investing in reducing their carbon footprint.

Owner: Shorenstein
Architecture, Interiors, Sustainability: Stantec Architecture
Structural Engineer: Odeh Engineers
Building Envelope Consultant: Sgh
Mep/Fp Engineer: Cosentini Associates
Geotechnical Engineer: Mcphail Associates
Civil Engineer: Nitsch Engineering
Landscape Architect: Copley Wolff
Lighting Consultant: Lam Partners
Contractor: Lee Kennedy Co.

Project Overview:
80 West Broadway is a 5-story mixed-use office building with retail and commercial uses on the Ground Floor. The design strategies used for reducing the GHG emissions and lowering the embodied carbon included, but are not limited to:
• Preserving the corner of the existing 1890 iconic 4-story masonry and copper façade, “Amrheins Building” — merging new and old elevations together in a cohesive design.
• Schematic design studies of (3) structural systems — resulting in choosing mass-timber glulam framing and CLT panels.
• Designed the exterior rainscreen system with thermally efficient materials, including mineral wool board insulation, thin brick, and thermal-bridging isolation clips.
• The lighter weight of the thin brick allowed for a lighter – and lower embodied-carbon – structural system and concrete foundation.
• The resulting lighter, thinner structural members also allowed for larger windows – and more use of internal daylighting.
• Designed the interior to celebrate the mass timber structure and leaving it exposed for biophilia benefits — which also reduced the embodied carbon of interior finishes and material-waste.
• Specified carbon-conscious materials, including low-carbon concrete.
• Specified energy-efficient, electric building systems.
• Planning for on-site renewable energy with rooftop solar photovoltaic panels.
• The LCA analysis will be used to achieve LEED certified Gold for the project, with the credit for Building Life Cycle Impact Reduction.

Replicability:
• Include community outreach in pre-design and early schematic design phases to discuss items valued by the community of the project’s site and/or existing building. The team may discover opportunities – as we did — to adapt or reuse an existing building, or portion thereof, as opposed to its demolition, transportation, and disposal; and eliminates need for fabricating a new façade with new embodied carbon materials.
• Utilizing wood framing, lighter in weight and with a lower carbon footprint — in lieu of a heavier steel and concrete structural system – allows the concrete foundation to be reduced in size – further reducing embodied carbon, and reducing labor-time and fossil-fueled transportation trips for installation.
• Building uses “thin-brick”, lighter in weight than standard brick, enabling a lighter-supporting structural system
As a result of reducing material weight and quantities, and reducing the time-duration of demolition and construction – the project reduces embodied carbon by reducing worker’s car-commuting trips and reducing on-site fossil-fuel powered machinery.
• Project specifies low-carbon concrete and electric furnace fabricated steel.
• Perform multiple, early structural system studies with cost and embodied carbon metrics to help the entire design and ownership team evaluate alternate system options along with their environmental impacts.
• Include early code analysis of building construction types to determine approach for fire-resistance ratings and where exposed structural framing is applicable. Analysis should include early discussions with the AHJ and involve them as a critical partner in the design-process.
• Include early thermal envelope “backstop calculations” to help determine the “sweet-spot” of material thicknesses and quantities, i.e. the proper amount of exterior materials such as insulation — achieving the required thermal efficiency of the envelope, while minimizing excess embodied carbon.
• Plan an efficient roof layout of equipment and solar PV to efficiently locate heavy-load roof framing.

Cost Effectiveness:
The design, envelope, structural, and building system decisions made by the project team led to cost-effective measures that include, but not limited to:
• In our early structural cost analysis, we determined that an all mass timber structure with glulam framing was less expensive in construction costs than a hybrid structure with steel framing. It was also determined to reduce the construction schedule’s time-line, imparting additional project cost savings.
• As previously mentioned, reducing the project’s time-line and overall on-site duration reduces embodied carbon – and reduces associated costs — by reducing the on-site worker’s car-commuting trips, material transportation trips, and reducing use of on-site fossil-fuel powered machinery.
• In cold-climates such as Boston, avoiding the winter season means being able to avoid the use of fossil-fuel powered temporary “winter-heating” during construction – reducing costs.
• Maintaining the mass timber structural framing exposed as part of the finished space saved project costs related to interior finishes and metal framing.
• Project utilizes car-parking stackers in lieu of a second underground level of parking; and utilizes a traction-elevator in lieu of a hydraulic-elevator. Thus, less excavation is required for installation. Less excavation, less carbon, less cost.

Innovativeness:
• 80 West Broadway leveraged the innovative possibilities of a mass timber structure by incorporating it as an important design feature for its design. Wood provides a range of environmental, social, and economic benefits. Wood elements require less energy to produce than concrete or steel, reducing embodied carbon. Mass timber also offers warmth and organic beauty, linked to increased productivity and quality of life for its inhabitants.
• The preservation of the existing façade was a community-led design partnership. The design team figured a way to reuse and structurally support the two walls at the corner while weaving it into the fabric of the new elevation design. This “facadectomy” is an innovative feature adding historical significance to this new building and creating an iconic landmark rooted in the “Southie” neighborhood of Boston.
• Synergetic effects of utilizing “thin-brick” for the façade: lighter-weight façade material allows for lighter supporting framing system, and a lighter concrete foundation – factors exponentially reducing the project’s embodied carbon.
• In order to understand the range and usability of available LCA programs to inform our decision-making, prior to the utilization of the “OneClick LCA” program reported here, our LCA analysis team explored the “Athena” program. Results varied between the two programs (Athena reporting a 27% reduction), possibly due to varied material choices between the two programs.
• We have learned through this endeavor, regardless of the LCA program, that a key factor in attaining quality comparison-reporting between the baseline and the proposed building lies as much with the accuracy of the alternative materials and quantities entered in the baseline model, as with those entered in the proposed model.
• Next-up, we intend to explore the “Tally” program.

Project Owner: Skanska CDUS
Project Architect: CBT
Contractor: Skanska USB
Civil Consultant: Nitsch
Landscape Consultant: Ground
Structural Consultant: McSal
MEP/FP Consultant: Cosentini
Façade Maintenance: Entek
Tel/Data/Security: LEDG
Sustainability: Thornton Tomasetti
Envelope Consultant: Socotec
Lighting Consultant: Tillotson

Project Overview:
The 380 Stuart Street project is a new 807,000 square foot class A office building being developed in Boston. The building is designed as a new paradigm for healthy office buildings as well as delivering an operational Net Zero carbon building. The design team focused on both material selection and cement replacement but more importantly on how to design a building in both a flexible and efficient manner as it relates to embodied carbon.

Concrete cement replacement was an obvious place to focus material use and investigate where and how much could be replaced. Given the multitude of concrete types and strengths coupled with construction phasing the team was able to substitute 50% of cement with a lower embodied carbon option for a large portion of the concrete work. In addition, we were able to reduce the remainder of the concrete including the massive slurry walls with 30% cement replacement. This approach gained us a 16% reduction of the concrete global warming potential equivalent.

Beyond material replacement, the design team determined early on design decisions that would make an impact beyond material replacement strategies. We focused on the vertical envelope of the building, more specifically economizing and reducing our embodied carbon footprint. First, we studied different curtainwall sizes, trying to find the optimal panel while maintaining the design intent. We developed a Grasshopper script that allowed us the perfectly tune the curtainwall panel width from 5’ to 6’ with the profile of the building, ultimately reducing the number of panels per floor by 22. Although the overall façade area did not change, the reduction of aluminum within the curtainwall as well as the shipping and installation of fewer panels is impactful. As the project progressed through the Construction Documents phase, we delved deeper into the details that again we believed could make an impact. We studied and developed parts of the envelope where we could reduce glass use, eliminating aluminum mullions where possible and even evaluating what appeared to be a minor connection detail of our guardrail. Ultimately, we were able to integrate more efficiently into the curtainwall with a 27% carbon reduction of the vertical envelope. In total, we achieved a 14.4% reduction in the global warming potential equivalent of the whole building.

Replicability:
Replacement of cement in concrete is a verified and impactful way to lower a projects’ embodied carbon, significantly. The difficulty lies in the availability of tested and available replacement materials within concrete sub-contractor market in a specific region. We discussed and collaborated with the general contractor to understand what would be available to us in this market and to evaluate areas where getting to 50% cement replacement would be structurally feasible as opposed to a lesser percentage of cement replacement for all the concrete in the building. This also required tight coordination with the construction schedule to identify areas where the cement replacement curing would have less of an impact on the overall project schedule. Since we set this as an early goal in our sustainable workshop, the team was able to develop an effective schedule and cement replacement that had a significant impact.

Beyond cement replacement, we studied how to reduce the quantity of concrete. We designed the concrete core with 3 structural bays where each bay could be replaced with a lighter steel structure if our wind tunnel results were favorable. This meant the team had to design the core to be flexible enough to accept the steel and composite metal deck without a re-design of the spaces, which could have caused a delay. This is in effect a design flexibility strategy that may allow some options to reduce a projects carbon footprint.

Lastly, we focused on designing the vertical envelope to reduce embodied carbon as much as possible without sacrificing our operational energy efficiency or primary design intent. The analysis we did with the width of the unitized curtainwall panels and tuning the panel width to work best with the massing is easily replicable due to the script we wrote for future projects. Although the area of façade did not necessarily change, our focus shifted to efficiency not only within the panel itself but also thinking through what would happen in the fabrication and construction process. Therefore, we intentionally set out to reduce panel quantities as this reduced the crating, shipping, on site installation and crane pick reductions.

Cost Effectiveness:
The concrete replacement does not appear it will be a reduction in cost, although depending on local market, replacement of cement to some percentage is generally replicable. The real cost impact on this project was the strategies focused on the vertical envelope. The redesign of the façade articulation, eliminating vertical mullions and spandrel opaques areas with metal back pans made a large contribution as well as an impact on the thermal performance of the envelope. However, we believe the best outcome was in the tuning of the façade panel widths to minimize the number of panels used while maintaining a proper cadence on the inside for future tenant layout flexibility. The panel quantity savings, although not part of this report, reduced the number of required panels by 528 overall, 22 per floor. The enclosed report does not necessarily capture the crating, shipping, and on-site handling, including crane picks, of the reduced panel quantity but we believe it is a significant embodied carbon savings. This methodology of considering the facade panel size relative to design intent, wall to floor ratio, shipping, and on-site logistics in an easily replicable embodied carbon reduction strategy that can be applied to most projects of this scale.

Innovativeness:
Our philosophy with regards to reducing embodied carbon is adapting. We are not only focusing on smart material selection but also emphasizing efficiency in design. Ultimately, this leads to a simpler, lighter, and less material intensive design. The manifestation of this strategy is our approach to the development and fine tuning of the façade. The key tool that allowed us to study various façade options was the script we developed in Grasshopper coupled with Rhino in Revit. The flexibility, quick results, and variations the script afforded us allowed us to assess in real time options that were worth investigating further to understand their embodied carbon footprint. Beyond the envelope, we were also able to reduce our concrete footprint by designing the core and surrounding space and structure in such a way that if we were able to remove one entire concrete core bay away and replace it with steel, the plan impacts were negligent.

Owner: North Cambridge Partners
Architect: Merge
Engineer: Odeh Engineers
Contractor: Not yet selected

Project Overview:
2400 Massachusetts Avenue is a planned mixed-use (residential/ retail) building in Cambridge, MA. The project is designed as two buildings, joined by the ground floor slab and underground parking garage. Between the two buildings, there is a retail canyon, designed to create pedestrian flow, and support commerce in the retail business that occupy the first floor of the buildings. The five floors above the residential space are 56 dwelling units. The project prioritizes private outdoor space for residents as well as tiered geometry to help the building flow visually with its surroundings.
Major parameters for the reduction of embodied carbon included replacing slab with CLT, exchanging OSB for CDX, Exchanging polyiso for TimberHP, and selecting windows and curtain walls with reduced virgin aluminum.

Replicability:
The repeatability of these strategies seems readily possible assuming dimensions allow. The post-tensioned slab design was very challenging, and in a more rectilinear building, identifying more specific impacts and efficiencies would be even more available.

Cost Effectiveness:
CLT assemblies are installed faster than Post tensioned concrete, and also provide the opportunity for exposure as interior finish, we feel this would be the largest financial savings opportunity.

Innovativeness:
The form of this project is so wild that coming up with innovative solutions while still in design development was a challenge. We do feel good about the CLT option over post tensioned concrete, but in the larger scope of buildings at this scale, this may or may not be very ‘innovative’.

Owner: Amherst College
WBLCA modeler: Introba
Architect: Sasaki/ Herzog and de Meuron
Engineer: Silman
Contractor: Shawmut

Project Overview:
Early studies for this project included embodied carbon analysis. Multiple scenarios were studied such as demolishing the entire existing science building and rebuilding with concrete and steel, demolishing the existing structure and re-building with steel, and at least three primary re-use scenarios that quantified the impact of keeping both the foundation and two or three floors, or the entire existing concrete structure. The final design solution re-used two of the existing concrete floors and the foundation with a mass timber transfer table above, topped with two floors of mass timber, results in a significant reduction of 33% from a baseline steel structure building.

Other aspects of the building materials carbon impacts were studied and quantified – including an evaluation of timber cladding and a combination of aluminum panel and brick cladding assemblies. The team learned that the facade choices had a more substantial impact with a greater % reduction for the steel baseline building, for the final design solution, the enclosure material choices had a much smaller impact of around 2% overall. The use of CLT structure also reduced the embodied carbon impacts from concrete by roughly 10%. By reusing two floors of the existing buildings’ concrete structure and foundation, and by using mass timber above, the greatest reductions were in upfront carbon – with an impact close to 60% less for A1-A5 from the steel baseline building. The reduction in upfront carbon aligns with where we need to reduce GHG emissions – immediately and in the short term.

Replicability:
The biggest lesson for this project is that early analysis can significantly influence the final design choices for a client who is seeking to significantly reduce carbon impacts from building construction. Also, early analysis serves to quantify which parts of a building have the most usefulness in reducing upfront carbon. For this project, re-using the foundation had a bigger impact than expected due to the site’s level change: one side of the building has the third/ timber level at grade and the other side has the lowest concrete floor at grade. Replacing this earth-retaining foundation would have proven to be carbon intensive.

There are many existing buildings across the Northeast that were built with concrete structure during the 1960s and 1970s: these buildings’ structure could be partially re-used, and their foundations retained. The use of a transfer CLT table enabled a flexible column placement on the upper levels that worked with the program and was not driven by alignments with the existing column grid. This project also proved that an integrated design team of two architecture firms, a structural engineer who has expertise in early carbon analysis workflows, a construction partner with experience with building reuse, and sustainability consultants with expertise in WBLCA working together on conceptual studies with a focus on embodied carbon are a winning recipe for big reductions in upfront carbon.

Cost Effectiveness:
The use of an integrated design team with a focus on embodied carbon analysis at early phases can be replicated on other projects. When there is an interested client, studying and analyzing the impacts of various scenarios during conceptual design can result in innovative and beautiful reuse solutions. The design team for this student center hopes that the innovative approaches taken for this project and its resulting dramatic reductions in upfront carbon, can be pointed to as a strategy worth studying for other campus or commercial existing buildings of this era of a similar construction type. Existing buildings are a cultural resource and the patina of age or a building’s history of use cannot be easily replicated in 100% new construction.

Innovativeness:
The team used the BIM model in an innovative way. The new architectural element area and volume takeoffs were extracted from the BIM model by Sasaki and tracked in a spreadsheet “LCA Data Input Tracker” which could be updated quickly as the design evolved. The existing structural elements were also modeled to enable accurate takeoffs, allowing the BIM model phasing to track elements that were to be demolished or re-used for carbon scenario calculations.

New CLT structural elements were also modeled by the structural engineer in BIM and the LCA modeling team used this model to do takeoffs for the CLT case. The structural engineer also used BIM to estimate material quantities for the baseline steel case which was also populated into the LCA Data Input tracker spreadsheet. Using BIM, in combination with spreadsheet tracking, enabled the LCA modeler to override the default quantities in OneClick LCA where these defaults did not match the BIM model and drill down to reveal more opportunities at a granular level to reduce embodied carbon.

Biogenic carbon accounting is another area of innovation. The ISO standards referenced by LEED assume that wood does not degrade at end of life, thus wood would have a negative value for product stage A1-A3. Other standards see wood differently. If biogenic carbon was “counted” as a negative, this would amount to about a 40% credit towards the project’s whole life carbon impact.

Pennrose,
Innova,
DiMella Shaffer,
L.A. Fuess Partners,
R.W. Sullivan Engineering,
enviENERGY Studio,
Building Science Corporation

Project Overview:
Originally constructed in 1913, Blessed Sacrament Church operated as an active parish until its closure in 2002. Once it was decommissioned, the pews, windows, and other decorative elements were removed and relocated to other Catholic churches in the area. The Hyde Square Task Force (HSTF) eventually acquired the abandoned building with the goal of transforming the structure into a performance space. That plan proved financially infeasible, and HSTF sought a partner to redevelop the existing Church as a mixed-use development in 2021. Pennrose, with a proposal for 200-person community space, and 55 units of much needed affordable housing, was designated as the development partner and has since achieved both zoning and permit approvals, as well as City and state financing awards, to support this preservation/new construction project.

The structural reality of the building necessitates the construction of a new steel frame inside the church shell. The steel frame will tie into the existing masonry shell, providing structure to both the existing building and the new construction being built within. The rear apse of the church behind the dome will be reconstructed, and new residential additions will be added to both sides of the building. The design approach maintains respect for the structural stability of the historic cross-form of the original building, while maximizing the residential area and ensuring the structural stability of the historic dome.
The three primary embodied carbon reduction strategies include: adaptive reuse, limiting future extensive renovations by preparing the building today to be Net Zero Ready, and evaluating the total carbon impact, which includes both operational and embodied carbon. The team utilized various tools, such as Tally for WBLCA, One-Click for isolated analyses, and the CARE (Carbon Avoided Retrofit Estimator) Tool for the total carbon impact.

Replicability:
According to the 2020 Massachusetts Buildings Sector Report, the building stock has grown by 16% since 1990 and there are more than 2 million individual existing buildings in the Commonwealth. Transformation of abandoned buildings represents a repeatable approach in cities like Boston with older building stock. Many of these existing buildings have an important presence for communities and are not easily replaceable by demolishing and building new. Furthermore, the redevelopment of the Blessed Sacrament Church, a landmarked building, creates a meaningful precedent for transforming structures that typically have too many permitting requirements to be politically and/or financially feasible. We hope that the approval of Blessed Sacrament as affordable housing creates a new standard for similar historic structures.

Throughout the design process, the team balanced many variables, including meeting the 2023 Stretch Energy Code and preserving as much as possible of the existing structure and load bearing masonry walls. EnviENERGY Studio, the sustainability consultant for the project, estimates that over 60% of the existing structure will be reused and restored. Additionally, lower embodied carbon selections include HFO blown closed-cell spray foam in lieu of HFC blown insulation, spray applied cellulose insulation within the existing church attic and above the existing dome ceiling, up to 25% supplementary cementitious materials in concrete, and recycled content in steel.

At the end of 2020, Massachusetts outlawed HFCs (hydrofluorocarbons), a common blowing agent for spray foam. Instead of an HFC agent that has a global warming potential of more than 1,000 times carbon dioxide, it is replaced by an HFO agent (hydrofluoroolefin) which substantially decreases the global warming potential to 1, based on an HFO product manufactured by Huntsman.

The team explored a comparison between HFC, HFO, and mineral wool insulation in BEAM, One Click LCA, and Tally and the results varied between all three platforms.

Cost Effectiveness:
Revitalizing Blessed Sacrament Church into apartments presents a financial challenge intertwined with historical preservation. Our goal is to achieve two seemingly opposing objectives: maintaining the church’s historical character, which requires adhering to strict guidelines, while incorporating modern features to meet sustainability targets and keep long-term costs low.

Despite these challenges, reusing the existing masonry shell offers a significant historical preservation advantage. To ensure long-term value, the project prioritizes the use of durable and sustainable materials for the exterior, roof, and other finishes. While repointing and roof replacement add upfront costs, these high-quality materials will minimize long-term operating and replacement costs, leading to a lower overall carbon footprint. The project is currently pricing 100% repointing of the existing brick and re-sheathing and replacing 100% of the roof historic clay tiles with a simulated clay barrel tile fabricated from recycled HDPE and LDPE plastic.

The historically significant metal windows are inefficient. The project team initially aimed to replace them with cost-effective uPVC windows. However, to maintain historical accuracy, the current plan is to use uPVC windows only in the new addition and create custom triple-pane metal replicas for the existing windows, resulting in higher project costs.

To understand the impact of windows Ekotrope software energy models were generated to compare uPVC and Aluminum . The replacement triple pane replica windows are less efficient than the standard double-pane uPVC windows specified in the new addition. This translates to higher energy consumption, utility bills, and embodied and operational carbon emissions for future residents in the original building.

The strategy to salvage existing features like lighting and wood details for the planned residences /community spaces presents potential cost-saving opportunity. While specialized labor is required, which can be more expensive upfront compared to using new materials, adding unique character, and potentially offset some renovation costs.

Innovativeness:
The 2023 Stretch Energy Code, and both Boston’s Article 37 and BERDO (Building Emissions Reduction and Disclosure) requirements need to be evaluated along with reducing embodied carbon emissions. It is not one or the other, but rather a delicate balance. The building’s proposed high-performance envelope and building systems are a response to the rigorous Stretch Energy Code requirements for an existing building change of use and addition, including the incorporation of thermal bridge derating as well as meeting the new envelope backstop requirements. The proposed solution improves the existing envelope performance, which in turn decreases the heating and cooling loads, but also sets this building up for the future by incorporating all-electric systems and infrastructure.

Under the ASHRAE 90.1-2019 pathway, R.W. Sullivan estimates that the existing building and addition are 29.7% better than a baseline building, establishing “Net Zero Ready” status per BE+ definition. By 2035, the predictive carbon emissions intensity (pCEI) is estimated to be 1.1 kg CO2e/sf, which also considers a future “greener” grid. This is a critical component, because further comprehensive renovations result in additional financial and carbon costs. We are preparing the building for tomorrow.

The adaptive reuse of an historic church reactivates connection with the greater neighborhood through a dedicated 7,000 square foot community space. Additionally, the resident lounge on the fifth floor will be located beneath the beautifully restored existing dome. This project thinks not only about adaptive reuse, but also interior modernization, adds usable space within an existing church shell, upgrades the existing shell and building systems, significantly addresses improved energy performance, and preserves an historic building through its evolution.

CREA/Citizens (LIHTC Equity Investor),
MassHousing (Lender),
Leggat McCall Properties/Joseph J Corcoran Company (Developer),
BHA (Land Owner),
Suffolk Construction (GC),
Stantec (Architect),
RDH Building Science (Enclosure and Passive House Consultant),
Petersen Engineering (Engineer)

Project Overview:
Building M is the first of 15 new buildings in the Bunker Hill housing redevelopment project, promising 21st century comfort, energy efficiency and carbon-reducing performance in a new mixed-income residential community. It replaces 42 aging buildings, the largest public housing project north of New York City, with new construction residential buildings, plus retail and community space. To strengthen the sense of community, the project features extensive green spaces and improved connections to the surrounding area.

Building M will stand up to six stories with 102 deeply affordable public housing replacement units. It has achieved PHIUS/Passive House Design Certification, and is pursuing full Passive House certification.

The primary embodied carbon reduction strategy for the project is the 7 layer Nordic X-Lam Cross Laminated Timber (CLT) for all above grade floors, replacing standard concrete plank. The project achieves 84 tons of CO2e/m2 reduction in embodied carbon in our primarily structural assessment. This equates to an impressive 44% reduction within the scope of our analysis, a percentage we know would drop if more components were included (see the full report attached at the end of the BHH Bldg M – LCA pdf). Also inspiring is the 1,358 tons of biogenic carbon storage attributed to the CLT, recognizing there are limitations with claiming biogenic carbon savings.

Of note, over 50 of the products in the project have EPDs. Most importantly, the two concrete ready mixes have EPDs, produced by Boston Sand and Gravel, and the cement for the precast has an EPD.

Replicability:
CLT is highly replicable given its ability to replace a more traditional steel and concrete structure. The aesthetic beauty of the exposed wood supports the decision to use CLT for reasons other than sustainability. Unfortunately, MA state code still requires the project to cover the CLT where there is a drop ceiling, but our hope is that the code will evolve to eliminate this requirement and therefore avoid the embodied carbon penalty associated with the gypsum board required to cover the CLT.

The primary challenge in using CLT for this project is with weather protection for the wood during construction, ensuring appropriate wood moisture content control.

Cost Effectiveness:
An important tenet of the project is that all buildings are constructed with the same construction technique regardless of the building height, in order to increase construction efficiency and produce high-quality buildings. Given that context, the project team evaluated different structures for Building M that could also be utilized for high-rise buildings (up to ten stories), largely structural steel with concrete plank (wood stick was not an option). CLT is a cost premium to dimensional lumber construction, but the project team realized savings compared to concrete plank. The standardization of the building components will drive efficiency and cost savings over successive buildings.

CLT’s constructability also contributed to a significantly shorter construction period, which reduced the cost of project general conditions and the interest expense. As the project team takes lessons learned to the future buildings, there will be opportunities to improve upon the successes of Building M.

Innovativeness:
The project team pursued innovative ideas throughout the development, design and construction processes. Innovation began with the financing of the project, which will leverage 1,689 market rate units in financing the redevelopment of 1,010 deeply affordable units. In design, the team was able to take a broader perspective than normal because the project is not a single, one-off building—the reduction strategies implemented will be refined through experience and replicated over every building in the development. Offsite fabrication was extensively explored and is another benefit of the CLT. The exterior wall panels are also fabricated offsite. More extensive prefabricated interior “pods” were investigated, but not selected for labor reasons.

Precast concrete is used for the stairs and elevator towers, as opposed to employing traditional CMU block. The precast concrete provides shear protection, avoiding the need for additional shear walls, and eliminating the need for temporary vertical access. From an embodied carbon perspective, one big opportunity for future innovation is with regards to the VRF system, which inherently contains a lot of refrigerant piping throughout the building. Our hope is that we can identify opportunities to reduce refrigerant piping on successive buildings.

Architect: BH+A
Structural: Foley Buhl Roberts & Associates
Sustainability Consultant: The Green Engineer Inc.
Owner: City of Newton
Contractor: J&J Contractors

Project Overview:
Construction of a new senior center of approximately 32,000 sf, three story building on a 26,000 sf corner lot. The building contains an above ground gymnasium with suspended walking track, multiple purpose room, kitchen, game room, fitness, activity spaces and an outdoor roof deck. The Cooper Center for Active Living project’s optimization strategy was to use timber and wood to the greatest extent reasonable in place of a typical steel and concrete structure. These optimizations include CLT decking and roofing, Glulam/PSL beams, LVL beams, wood stud framing, and wood I-joists. The optimization resulted in 27% reduction in embodied carbon when compared to the baseline.

Two early analyses were done in SD and DD to determine which direction the design team should take reduce both its embodied and operational carbon:
1)An analysis in SD was done to compare the combined embodied and operational carbon savings from a new building vs. an add/reno building. The new construction building had an estimated 25% higher embodied carbon, but was much more efficient and the net carbon savings would come after 7.4 years.
2)After the 1st analysis convinced the team to pursue the new construction option, a 2nd analysis was requested in DD to compare a majority timber frame building to the average steel and concrete building. This analysis at the time showed that the timber frame option had an estimated 48% reduction when compared to the steel/concrete option.

Replicability:
The reduction strategy of including the early analyses in the design process is easy to replicate, but the results will vary from project to project since there aren’t standards we can reference yet. This just means the results will be more project specific, but will still give reliable results in making embodied carbon reduction focused decisions. The City of Newton asking for the design team to report embodied carbon AND reduce embodied carbon was the biggest factor in the project implementing embodied carbon reduction strategies.

The reduction strategy to design a building with a structure that uses timber and wood to the greatest extent possible is entirely replicable. Not every project will be able to use as much timber and wood as the Cooper Center project did, but there are certainly structural assemblies, such as floor decks and wall framing, in almost every project that can be designed with timber or wood instead of steel and concrete. Not only do these strategies reduce embodied carbon, but when done right, they can reduce weight and cost.

Cost Effectiveness:
A mass timber structural system with stick wood framing is significantly lighter structurally (~50% to 75% lighter) than a steel and concrete structure. The overall lighter weight also reduced both the sizes and weight of the supporting foundations and footings. The lightweight design helped to eliminate otherwise needed ground improvement where soil conditions at the project site were poor—up to 8 ft of urban fill and needed extensive ground reinforcing, such as rammed aggregate piers (RAP) with a heavier steel and concrete building.

The timber frame structure will be panelized, manufactured offsite, and assembled in a much shorter schedule than a steel and concrete building: ~4 months shorter.

Given the size of the building at 32,000 sf with fully sprinklered fire protection system, the project was classified as a Type 5 construction and benefited from reduced cost and added design flexibility. A steel and concrete building of type 1 or 2 classification would have significantly higher cost and fire requirements: ~15-20% higher.

Innovativeness:
The Cooper Center for Active Living project was constructed using a wood framed construction with glue laminated timber frame, Cross Laminated Timber (CLT) decking, and a light frame stick wood wall framing system. The Glue laminated timber frame was ideal for long spans and was used over the raised gymnasium track to provide a clear span of over 65 ft.

Aside from the timber frame structure, which is not an industry average structure type, but would be seen as typical for a timber frame building, the real innovation in this project came from the early analyses that were done. The City of Newton really pushed from the project team to analyze and report on a couple of options to ensure the project would meet optimal operational and embodied carbon. This began with analyzing both the operational and embodied carbon impacts of constructing an addition/significantly renovating the existing building vs demolishing the existing building and constructing a new, highly efficient, typical steel and concrete building. The analysis showed that the add/reno option had a ~25% embodied carbon reduction vs the new construction option which would have a ~38% operation carbon reduction and would have a net carbon savings after 7.5 years. This convinced the town to pursue the new construction option, but they wanted the team to pursue a timber frame structure from the beginning, due to its well-known embodied carbon savings over structural steel and concrete, and requested another early analysis in DD to confirm the estimated embodied carbon savings. At the time this analysis showed ~48% reduction in embodied carbon.

Owner-Harvard Real Estate,
Project Manager-Tishman Speyer,
Architect-Studio Gang Architects,
SMEP engineer-Arup,
Contractor-Consigli Smoot Construction,
Sustainability Consultant-Perkins+Will,
Civil Engineer-Nitsch Engineering

Project Overview:
The David Rubenstein Treehouse is an approximately 54,000 gross square foot conference center in the Allston neighborhood of Boston, MA. The building is Harvard’s first University-wide conference center and will become “a focal point for programs ranging from international summits to alumni events, conference receptions, and workforce recruiting activities” as per the University. The Treehouse has holistic sustainability goals that address climate, health and equity. Besides efforts to significantly reduce the operational energy/emissions use from a baseline building, the design team has also focused heavily on reducing the embodied carbon impacts of the building. The building has an estimated 55% reduction in embodied carbon from an equivalent baseline building which equates to an estimated 18 years of operational carbon emissions savings.

Harvard’s vision for the project was to address climate, health and equity and the project team aligned behind this vision so all aspects of the embodied carbon reduction strategy focused on reducing fossil fuels, yet ensuring that health and equity were also considered and not compromised on any major decisions. The majority of the decrease in embodied carbon impacts, as compared to a typical building of similar function, comes from the mass timber structure and optimization of the low -embodied concrete used in the ground slab, core-walls and foundations . The overall approach to the project After designing the building in mass timber, the team further pushed to reduce the impacts of the concrete by using ground glass pozzolan and other additives to reduce the cementitious content (95% of the emissions) of the concrete. The team also optimized the exterior envelope by using wood-cladding, specifying a glazing system that’s approximately 25% less in global warming potential than the typical curtainwall system, and making lower-GWP choices for insulation such as polyisocyanurate and other fiber materials in lieu of spray foam, XPS, and other high-GWP materials. These decisions were made in early design and diligently pursued throughout the process with the entire team (architects, consultants, GCs, ready-mix suppliers, etc.) constantly striving for even better performance.

Replicability:
While there are many unique features to the conference center, the project advances replicability by supporting new markets for low embodied carbon materials such as mass timber and GGP (ground glass pozzolan) cement replacement. By creating demand and proving feasibility, the project team has helped to grow the ecosystem of suppliers, manufacturers and contractors that are reducing fossil fuels and chemicals of concern so that the materials and methods used will be considered holistic viable options that can easily be replicated by others in the future.

Another key contributor to industry and market transformation was Harvard’s early decision to pursue aggressive, holistic sustainability targets, including embodied carbon, as part of the commitment to achieving LBC Core Green Building certification and the Harvard Healthier Building Academy requirements (indoor air quality and class-based chemical, e.g., PFAS, reduction in products) and LBC Materials Petal certification. To meet these goals, the client identified mass timber structure as the core element integral to the overall building design from the very beginning of the project. This early commitment allowed the project team to iteratively interrogate where improvements could be made in carbon reducing measures and engage experts and suppliers early to inform design and engineering throughout the design process.

Harvard and the project team advocated for low embodied carbon products that reduce fossil fuels and reduce chemical classes of concern (e.g., PFAS, chemical flame retardants, antimicrobials) where possible. The low embodied carbon concrete was innovative as it replaced cement with ground glass pozzolan instead of traditional fossil fuel intensive replacements (e.g., fly ash, a toxic, byproduct from burning coal and slag). The contractor and suppliers supported informed decisions and reduced perception of risk. Performance tests that were piloted for this project can be used for future ones.

In addition to the timber and GGP low embodied carbon concrete, the team also implemented common sense design decisions that had meaningful impact on reducing material volume overall and therefore embodied carbon. Structural member sizes were optimized, basement areas minimized. The team integrated a demountable (reuseable, circular) raised floor system above CLT floors throughout to conceal the major building systems, and minimize need for beam penetrations and associated beam upsizing. The raised floors also serve the displacement ventilation system, which reduces the amount of sheet metal ducts and operational energy use, and improves indoor air quality.

Cost Effectiveness:
The early decision to adopt mass timber as the primary structural system allowed the team to reduce the overall building weight and as a result reduce the amount of concrete volume needed for foundations.

Multiple timber suppliers were engaged early in the process for competitive bidding and onboarded as design assist partners to support the refinement of the structural design. By establishing a collaborative dialog with contractors and engineers, all partners became familiar with the design and shared common goals for the project. This early engagement was instrumental in managing costs and reducing perceived risks.

The Owner and Design Team set an ambitious target for what can be achieved with GGP concrete mix, and engaged with the right partners who were eager to learn, experiment, and advance. Working with concrete suppliers during design phases on the project’s cement replacement goals and strategies was instrumental for the contractor to avoid schedule delays and unforeseen costs. The use of Ground Glass Pozzolan (GGP) as primary cement replacement solution was ultimately only a 1.25% cost add to the total concrete budget which translated to a <1% added cost to total construction cost.

Mockups for both the timber and concrete elements were built in advance of start of construction to test out visual and performance criteria. Through this process, the design team was able to incorporate feedback and refine construction details further.

Innovativeness:
The Treehouse Conference Center embodies many “firsts” for the Harvard campus and in Massachusetts: it’s the first all-mass timber structure (Harvard), first to widely implement GGP cement replacement (Harvard and to our knowledge in Massachusetts), and first to pursue both LBC Core Green Building with Materials Petal Certifications (Harvard). The project achieves a 55% reduction in embodied carbon compared to a baseline project with an all-concrete structure based on the design.

The most innovative reduction was low-embodied carbon concrete without the use of fly ash. Fly ash is a byproduct from coal-fired power plants and therefore not a long-term sustainable solution for low-embodied carbon concrete. Structural concrete for foundations, retaining walls, and grade beams as well as architectural concrete core are designed to use a tri-blend of ground glass pozzolan (GGP), slag and cement with the GGP and slag resulting in replacement of 70% of traditional cement. Additional concrete mixes for slabs and shear walls will utilize slag as the cement replacement. In total, the proposed design for concrete reduces the project’s global warming potential by 20% below the NE Region’s National Ready Mix Associations concrete mix performance averages, without the use of fly ash.
The design process was innovative as well since the contractor and ready-mix suppliers were engaged early in the design phase to start the discussion on using GGP in the concrete design in collaboration with the Owner and design team (e.g. architect, structural engineer and sustainability consultant). Like the use of any new system or products, concerns and challenges needed to be worked through collectively, to prove the use of GGP in the project. Early engagement was critical to the success of using GGP and keeping fly ash out of the concrete mix designs.

DCAMM (Massachusetts Division of Capital Asset Management & Maintenance) – Owner
Massachusetts Maritime Academy – Client
Ellenzweig – Architect
B+AC – Structural Engineer
BR+A – MEP Engineers
The Green Engineer – Sustainable Design Consulting
Bond Building Construction, Inc. – Construction Manager

Project Overview:
This new, 36,000 GSF laboratory building at Massachusetts Maritime Academy provides science and engineering labs for General and Organic Chemistry, Biology, Physics, Strength of Materials, and Operational Controls. Facilities include teaching labs, prep and support spaces, a design lab and fabrication suite, Marine Capstone lab and Dynamic Positioning lab, faculty offices, and student gathering and break-out spaces.

Early Design Development: Benchmarking and Right-sizing are integral components of our approach. Our team focused on avoiding over-building space from the earliest design stages, demonstrating a commitment to efficient resource utilization and environmental responsibility. We also conducted a thorough comparison between different structural steel systems, ultimately opting for a mix of HSS and Wide Flange columns. While HSS columns initially showed slightly higher embodied carbon, their reduced surface area minimized the need for fireproofing materials, making their embodied carbon comparable to Wide Flange columns. Additionally, our exploration into low embodied carbon concrete led us to revise our concrete specifications to be performance-based, targeting a 25% reduction in GWP compared to regional benchmarks.

Product-Specific EPDs: We incorporated product-specific Environmental Product Declarations (EPDs) for interior products such as GWB and flooring finishes, ensuring low embodied carbon across all building materials.

Innovative Glazing Solutions: Embracing the new MA Energy Stretch Code requirements, we conducted a comparative study between aluminum frame triple glazing and fiberglass double glazing. Despite meeting energy efficiency standards, the latter demonstrated a 25% reduction in embodied carbon of a window assembly.

Replicability:
Our early design decisions, such as the selection of structural steel systems and concrete specifications, are based on thorough comparative analyses that can be easily replicated in future projects. The approach of assessing embodied carbon at the design stage allows for informed decision-making and can be applied to various building typologies and regions.

We also integrated CLF 2023 material baseline data into our embodied carbon reduction strategies. By focusing on the 20th percentile data, we have identified opportunities to reduce embodied carbon significantly. This approach ensures that our design decisions are grounded in robust data, enhancing their replicability across different projects and contexts.

Cost Effectiveness:
In our comparative analysis during early design development, we studied the cost implications of low carbon concrete vs conventional concrete and a mix of HSS columns and wide flange vs. all wide flange. We discovered that the difference in cost for both studies is negligible especially in Massachusetts. We are using wide flange where we have structural bracing only, to simplify structural connections.

Innovativeness:
The comparison study between aluminum frame triple glazing and fiberglass double glazing exemplifies our innovative approach to reducing embodied carbon. By challenging conventional assumptions and exploring alternative solutions, we identified a 25% reduction in embodied carbon of a single window assembly which resulted in 1% reduction in the whole building LCA through the adoption of fiberglass double glazing while still meeting stringent energy efficiency requirements.
By leveraging CLF 2023 material baseline comprehensive dataset, we were able to identify materials with lower embodied carbon footprints and integrate them into our design specifications. This data-driven approach ensures that our design decisions are grounded in evidence and aligned with industry benchmarks.

Owner: Northland Newton Investment Corporation
Arch: Stantec Architecture
Structural Engineer: Odeh Engineers
Contractor: Cranshaw Construction

Project Overview:
Across all buildings, the design team worked together closely to minimize the occurrence of structural transfers (that are generally inefficient) except at locations where functionally necessary. In building 7 specifically, beyond the use of a mass timber structural system, the team worked together to eliminate the concrete topping at the roof level, where it was not acoustically necessary. To do this, the CLT was used as the diaphragm at the roof level, in contrast to the floor levels where the acoustically necessary concrete topping was used as the structural diaphragm. Also, the 12″ reinforced concrete structural slab on grade was reduced to a 4″ soil supported slab on grade, with the structure and interior finishes detailed to accommodate any potential settlement of the slab. While this approach allows for future flexibility in the tenant/retail spaces, it also significantly reduces the amount of concrete in the slab and reduces the demand for the deep foundation elements, resulting in smaller pile caps with fewer piles.

Replicability:
According to the Civil + Structural Engineer media “The prototypical building of the future could likely be a combination of the trio: a building where floors, shear walls, and roofs are CLT; long span beams or beams under extreme loads are steel; and foundations and cores are concrete”. Low-carbon materials like gypsum board, plastic and mineral insulations, and optimized concrete mixes are available and the demand for these materials continues to add supply in the market. GWP product information is essential to compare materials and the cross-laminated timber industry is catching up with publishing EPDs. EPDs were not available for the selected timber product used in the design, but the team is following up with the manufacturer about the timeline to publish LCA information.

Cost Effectiveness:
The use of mass timber superstructure often results in construction schedule savings. Cost information was not available for this submission, however, Cranshaw Construction, the construction manager, priced the typical specification materials and products and the low carbon alternates to quantify any cost differences and identify any supply chain, availability, or scheduling challenges, to determine which alternates can be feasibly incorporated into the project. Also, according to the Civil + Structural Engineer Media “CLT can be built between 25% and 75% faster than similar reinforced concrete and steel buildings on a square footage basis, has a 20% overall faster schedule, and uses 90% less construction traffic.”

Innovativeness:
Beginning early in design, the design team identified several lower embodied carbon material options to be analyzed for cost, schedule, and availability implications. Using the data included in the Carbon Leadership Forum 2021 Materials Baselines Report, specifications were written that identified lower embodied carbon targets than the average for structural and enclosure material components. These low-carbon specifications target the most dominant high-carbon materials including structural steel, ready-mixed concrete, insulation, and gypsum board. From there, Cranshaw Construction, the construction manager, priced the typical specification materials and products and the low carbon alternatives to quantify any cost differences and identify any supply chain, availability, or scheduling challenges, to determine which alternates can be feasibly incorporated into the project. Additionally, the design teams worked to ensure the structural systems were as efficient as possible to minimize the amount of structural steel and concrete on the project. Construction has not begun on Building 7, but we are excited to share other insights as the project develops.

Developer: Tishman Speyer/Breakthrough Properties,
Architect: Arrowstreet,
Structural Eng: McNamara Salvia,
Contractor: Turner, Janey, J&J joint venture

Project Overview:
OneMilestone is a core and shell lab/office building for life science tenants within Enterprise Research Campus which is transforming an industrial site into a vibrant mixed-use development. The project team set out to explore significant, cost-effective embodied carbon reductions in these types of commercial developments which dominate the region and are responsible for substantial embodied carbon.

By implementing multiple replicable strategies and cost-effective innovations, the project achieved a 22.5% reduction in global warming potential (GWP) compared to the baseline. The reduction stems from a 47.4% GWP reduction in foundations and a 12% reduction in structure. The Sustainability and LCA Consultant, firmly believes in creating a baseline that reflects the typical practices in Massachusetts for this type of large commercial building. Therefore, there are several low carbon solutions used in the project that are the same in the baseline and proposed so no carbon savings is seen in the WBLCA. For example, mineral wool insulation for walls, low GWP XPS insulation for roofs and below grade, and low carbon cladding. The items that are improved in the proposed are reduction in concrete and steel quantities, low-carbon CMU, and low-carbon poured-in-place concrete mixes which are 42.9% lower than the NRMCA Eastern Region Average.

As a core and shell project the WBLCA did not include interiors, however, there are several embodied carbon reduction strategies used for the interior. Material quantities were reduced by utilizing structure as finish with exposed ceilings and polished concrete floors. Where secondary finishes are used low-carbon options were selected such as FSC wood, wool for acoustics, carbon neutral carpet, and recycled-content metals, tile and drywall.
Additionally, beyond the WBLCA scope, low-carbon site improvements were incorporated, including site/roof pavers with ground glass pozzolan for cement replacement, FSC certified non-tropical benches, and site concrete 25% better than NRMCA ERA.

Replicability:
The design process involved three steps to reducing embodied carbon starting with the most impactful. These steps resulted in a low-carbon building and are easily replicable since they align with typical design processes, assemblies, and detailing.

First, was Optimizing Form and Structure. The team studied multiple solutions to decrease the steel quantity by reducing member sizes, using more but smaller columns, altering massing, limiting transfers, and adjusting cores and program locations. This effort resulted in a 10% reduction in steel tonnage. Creative solutions were implemented to reduce the concrete quantity including a variable depth mat slab, optimized support of excavation, and balanced strength and thickness of floor slabs.

The second step was to Use Less Material for enclosure and interiors. This approach ensures a 100% reduction of carbon and guaranteed construction cost savings. Strategies include balancing thermal performance of the envelope with operational carbon by providing insulation to the point of diminishing returns but not over insulating.

Third, was Selecting Low-carbon Materials by choosing better options of the same material or switching to different materials. The team studied the life-cycle impact of five cladding systems to identify select low-carbon solutions, considering factors such as cladding material, attachments, backup, and impacts on super structure. The project evaluated a mass timber structure but was not able to pursue due to building and fire code constraints. The project switched the CMU, which is used in cores and the parking level to Carbon X that uses carbon capture.

A whole building LCA was conducted with Tally during concept design to create a baseline and then updated in each design phase to confirm reductions. Throughout the design, optimizations and materials were assessed with comparative LCAs. During construction OneClick was used for the WBLCA so the final concrete EPDs could be input.

Cost Effectiveness:
The early design decisions for the project prioritized cost-effectiveness by focusing on reducing material quantities, specifically steel and concrete, since less materials means less cost. While cost optimization is part of standard design processes, the project’s studies were beyond typical practice but can easily and cost-effectively be replicated on future projects. The team evaluated multiple options for building massing, location of the cores, foundation types, and number and spacing of column grids. These options were then evaluated for their effectiveness in reducing the tonnage of steel and cubic yards of concrete required and associated embodied carbon. The team also evaluated whether there would be any downstream effects, such as increasing envelope structure and carbon, to make sure the reductions were completely achieved.

A performance concrete specification was developed with a 25% carbon reduction target over the NRMCA Eastern Region Average. Looking at available mixes and the market, the team felt this would achieve good carbon reduction with minimal additional cost. Once a subcontractor was selected the team continued to work with the ready-mix supplier to improve the 8,000psi mix as it is the majority of concrete on the project. However, there were no cost-effective lower-carbon mixes for 8,000psi from the local suppliers. The team worked with the ready-mix suppliers to develop a new cost-effective mix that also achieves unprecedented reductions in embodied carbon, even compared to higher-cost options. With this mix and the other low-carbon mixes for other strengths, the project surpassed the 25% target by achieving 42.9%.

The use of Carbon X CMU had negligible additional cost but the carbon reduction far outweighed the minimal increase. The low-carbon insulations, cladding and finishes had no additional cost implications for the project.

Innovativeness:
In addition to the simple yet atypical design process noted previously, there are several construction phase innovations for this project. Collaborating with the ready-mix supplier, a new mix for the 8,000psi mat foundation was developed that has 66% cement replacement and results in a 62% GWP reduction over the NRMCA ERA. The cement replacement is primarily achieved through slag which is preferred environmentally because fly ash is derived from the combustion of coal. All of the other mixes on the project exclusively use slag. There are carbon reductions beyond the new mix’s materials, a lower heat signature meant less crushed iced was needed for placement. Additionally, a moisture retention method in lieu of wet-curing, reduced the amount of potable water. Given the necessity for high strength concrete on many commercial building projects, this new mix has the potential to for wide-spread adoption, significantly reducing embodied carbon across the industry.

In a collaborative effort the contractor, design team, and the ready-mix supplier, engaged Sublime Systems for Sublime’s first ever field validation pour. Sublime Systems is a pioneer in cement manufacturing that is developing a means of manufacturing cement without fossil fuels. Through this validation pour, Sublime was able to confirm that this permanently-placed cement performed according to the ASTM C1157 standard performance specification for hydraulic cement. A major step in moving towards being ready for wide-scale use.

Further innovations related to concrete included diverting all of the waste associated with concrete and concrete washout and utilizing reusable materials for temporary protection and safety to reduce waste.

Throughout the construction, source separating of at least seven streams and materials diversion is significantly reducing landfilling of materials. Equipment and tool repair and reuse programs are also in place.

Client – Town of Brookline
Owner’s Project Manager – Leftfield
Construction Manager – Consigli
Architect – MDS Architects
Associate Architect/Landscape Architect/Civil Engineering/Sustainability – Sasaki
MEP – GGD
Structural – Souza, True & Partners
Envelope Consultant – RDH Building Science

Project Overview:
The Pierce School is a PreK – 8 School that will serve over 700 students in the Town of Brookline and being completed with the Massachusetts School Building Authority (MSBA). Located on a town parcel that featured three existing buildings, including a historic building dating to 1855, the town set high performance goals prioritizing indoor environmental quality for the Pierce School. In response, the design developed an Integrated and Holistic Design Framework that considers embodied carbon, operational carbon, student health + wellbeing, and climate resilience through the design decision making process.
Early in design, multiple design options were considered for combinations of using all, any, or none of the existing buildings. Some of these design studies included re-using and renovating the existing Brutalist building and adding a new addition, to demolishing both the existing building and re-purposing the adjacent historic structure for another Town use. In the end, the preferred approach demolishes the existing school building, and renovates the historic school building and connects the two with a pedestrian bridge.

Early whole carbon studies indicated that this approach would begin operational carbon savings after 15 years. During Design Development, the design team has continued to study ways to reduce upfront carbon through product selection and studying exterior enclosure with an eye to reduce embodied carbon. These reduction strategies include preserving a portion of the below grade parking garage and foundations, using composite deck at the roof only where equipment is located and metal deck without the topping concrete in other areas.

Replicability:
Every project offers its own opportunities for reducing embodied carbon emissions, and understanding what to consider and knowing where to look for reduction opportunities is easily replicable. When considering a site, considering what can be re-used and how can the project reduce as much upfront carbon emissions as possible? In the case of the Pierce School, the renovation of the historic building resulted in avoided upfront emissions as well as improving the operational carbon emissions of this historic building. The replicable strategies include re-using some of the existing below grade parking garage, using composite deck only where equipment is located on the roof, and utilizing 24 in stud spacing in lieu of 16 in spacing on the facade. These three strategies resulted in an overall reduction of 10% over a baseline building, and a surprising 22% reduction in the carbon intensity (kgCO2e/m2).

The historic building is being modernized, including being insulated from the interior and will be served by the project’s ground source heat pump system, so that it can continue to serve students and the town. The parking garage and a portion of the foundations will be partially re-used reducing the amount of new concrete needed for the building.

We are currently looking at products inside the building and ways to reduce quantities used and overall embodied carbon for the project.

Cost Effectiveness:
Going through a Feasibility Study where multiple design options were considered, many factors play a role in determining the preferred outcome. One of these is the overall project cost of each design option. The preferred option for this project fell somewhere in the middle of all the considered design options.

The more expensive project cost projects included building a new parking garage. This option would additionally have created more embodied carbon emissions as well. Many of the less expensive options considered renovating and reusing an existing brutalist concrete structure. The overall project cost savings of this option wasn’t determined to be great enough to give up the flexibility that new construction provided. Additionally, we had to consider that existing building was riddled with asbestos and would also need larger heating and cooling loads than a new building designed with passive house standards in mind.

Innovativeness:
From the onset of the project, the Town of Brookline has pushed the design team to be at the forefront of sustainability strategies for their new school. This includes the incorporation of ground source heat pumps for heating and cooling, and while the team has used analysis to make smart decisions within a holistic design framework enabling the project team to discover ways to reduce embodied carbon emissions. The innovative aspects of this project are the integrated design team that includes an associate architect supporting the architect of record with sustainability analysis from the concept stages through construction documentation. The collaborative team model is unusual yet can be replicated to bolster each other’s expertise and learn from each other.