North Campus Housing: Phase IVa
Case Study
2021
Whole Building Life-Cycle Analysis
University of Washington North Campus Housing INTRODUCTION TO LCA AT K I E R A N T I M B E R L A K E
To understand the full carbon impacts of building operations and construction, KieranTimberlake uses Life Cycle Assessment (LCA) to evaluate the embodied environmental impacts of building materials and assemblies. When paired with energy modeling, LCA is an important tool to help identify strategies to decarbonize our projects. LCA models measure impacts according to a range of categories, including global warming, acidification, eutrophication, smog formation, ozone depletion, and the depletion of non-renewable resources. When applied to the scale of a full building, WholeBuilding Life Cycle Assessment (WBLCA) can evaluate the embodied environmental impacts associated with the manufacturing of materials, the construction and demolition of the building, and the disposal of the materials after their use. At KieranTimberlake, WBLCA serves to help a project team make decisions to reduce the embodied environmental impacts of the project. WBLCA METHODOLOGY
LCA Scope: A1-3, B2-5, C2-4. This assessment occurred before Module D was adopted after the release of ISO 21930:2017. Included Model Scope: Superstructure, substructure, enclosure, and limited finishes as modeled in Revit and required by the LEED 4.0 standard
PROJECT OVERVIEW
The University of Washington North Campus Housing project is a 535,850 SF complex composed of three separate buildings. It is located on the steep slopes of the University of Washington’s North Campus in Seattle, WA. In addition to housing, the complex provides student accommodations, office spaces, a dining hall, a maker space, and other community amenities. Each building follows the same structural logic: five stories of wood framing over two stories of castin-place concrete construction. The envelope system is primarily a cedar slat ventilated rainscreen with perforated steel panel accents, and masonry veneer on the lower stories. This was the first project at KieranTimberlake to integrate WBLCA results into decision making to reduce the embodied environmental impacts of the overall complex. The first WBLCA for each building was completed at the 50% design development milestone in December 2015. Partial-building LCAs examined envelope options, structural components, insulation types, and roofing materials. A second WBLCA for each building was completed at the end of documentation before the project was issued for bid. The final WBLCA for each building was completed at the end of construction to account for the actual concrete mixes used in the built project. The final embodied carbon intensity of each building is 209.3, 229.5, and 323.4 kg CO2 /m2 . The average carbon intensity of the project is 252 kg CO2 /m2, a noteworthy improvement over the Carbon Leadership Forum’s 2017 baseline for multifamily residential buildings of 453 kg CO2 /m2, based on (66) models.1
Excluded Model Scope: Non-structural partitions and associated finishes, floor and ceiling finishes, railings (<1% by mass), casework, furniture, MEP, landscape elements, and site work. LCA Software and Version: Tally® version 2016.05.08.01 Reference Building Life: 60 years Biogenic Carbon: Excluded, as this assessment occurred before the release of ISO 21930:2017, the standard recommending the inclusion of biogenic carbon in WBLCA Module D Credits: Included
C A S E S T U D Y University of Washington North Campus Housing
KieranTimberlake
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12/16/2015
NORTH CAMPUS HOUSING - PHASE IVA 12% summary Full building
47%
Results per CSI Division
15% 3%
PROJECT FINDINGS
13%
18%
In the first WBLCA, the project team focused on identifying and reducing the sources of embodied carbon contributions in 29% the buildings. Although the struc-
7%
ture of the buildings by volume is primarily wood stud, the concrete construction
12%
components contribute the most to the environmental impacts of the buildings, 5% 47%
contributing over half of the embodied carbon. Through a collaboration with
the15% structural engineering team, the cement content in the concrete mixes was
3%
reduced by 50% during the remaining phases of design.8%
17%
24%
The other major contributor to the buildings’ embodied carbon was the upper
7%
level rainscreen assembly. In order to reduce the associated impacts Energy with this Demand Global Warming Potential Primary 5%
assembly, KieranTimberlake introduced a perforated patterning to the metal ac8% 24% cent panels, reducing the quantity of metal used in those panels by almost half.
17%
LegendGlobal Warming Potential
KieranTimberlake also detailed the frequency and location of fasteners in the Primary Energy Demand
panels to allow a lighter gauge of steel to be used for both the accent panels and the corrugated steel at the back of the rainscreen.
CSI Divisions Legend 03 - Concrete
With changes to these two elements, KieranTimberlake reduced the embodied
04 - Masonry
carbon of the building by over 30% before the start of construction.
CSI Divisions
03 - Concrete
04 - Masonry 05 05 - Metals
Metals
06 - Wood/Plastics/Composites 06 - Wood/Plastics/Composites 07 - Thermal Moisture Protection 07 and - Thermal and Moisture 08 - Openings and Glazing
08 09 - Finishes
Protection
- Openings and Glazing
09 - Finishes
OPPORTUNITIES FOR IMPROVEMENT
Life Cycle Assessment is an emerging practice. We view every WBLCA as an opportunity to reduce embodied carbon and evolve our practice, and we hold ourselves to the highest standard while conducing WBLCA. In the interest of ongoing improvement of our efforts and promoting LCA across the profession,
L C A R E S U LT S
The combined embodied carbon contributions of the three buildings at 50% Design Development. Concrete makes the greatest impact at 47%.
this project helped us mature our practice in the following ways: •
Keeping up with developments in biogenic materials and their carbon accounting leads to design decisions that lower embodied carbon
•
Assessing concrete mixes in the earliest possible design phase can greatly reduce embodied carbon
•
Metal coatings, even those on underlying metals, can contribute significant embodied carbon to a project and assessing them in early phases can yield reductions
In this first-ever use of iterative WBLCA on a project, KieranTimberlake followed the best practices as recommended in 2015, which did not account for biogenic
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carbon. As WBLCA practices evolved to include biogenic carbon, a study done now would show that advanced framing techniques to reduce the amount of wood likewise reduces a wood structural system’s capacity to sequester carbon.
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The project team was able to significantly reduce the embodied carbon of the cast-in-place concrete system by decreasing the percentage of the cement in the concrete mix design. Project teams who pursue embodied carbon reductions through concrete mix design should begin this process in the earliest possible design phase. Equally important at this phase is to engage the structural engineering team in embodied carbon reductions. In the five years following this work, KieranTimberlake has created even deeper reductions of concrete structural components’ embodied carbon impacts through this type of early, strategic structural interventions. The reduction of the metals in the rainscreen had an appreciable impact on reducing the embodied carbon of the building. Most importantly, it was the associated reduction of the metal coatings that had the most significance, even more than the underlying metals. LESSONS LEARNED
The design integrates indoor and outdoor spaces into memorable gathering places.
• Working towards environmental impact reductions in the earliest possible design phases is the most important intervention in a building’s embodied carbon output. • Any project containing concrete should reduce the cement content in each concrete mix, even when concrete is not the majority of the building structure by volume. • This study shows the importance in the updated LCA standards to include biogenic carbon sequestration when working with wood and other bio-based
REFERENCES
Simonen, K., Rodriguez, B., Barrera, S., Huang, M., (2017) CLF Embodied Carbon Benchmark Database, database. Available at http://hdl.handle. net/1773/38017. 1
ISO 14040-14044:2006, Environmental Management – Life Cycle Assessment. EN15804 – Sustainability of construction works – Environmental product declarations – Core rules for the product category of construction products. 2
PHOTO CREDITS
materials, as biogenic carbon should be considered as an essential source for potential carbon sequestration to offset embodied carbon in other materials. • Dematerialization is an effective strategy when applied to materials that contribute to an outsized proportion of the environmental impacts when compared to their percentage of the building’s mass. The other major contributor to the buildings’ embodied carbon was the upper level rainscreen assembly. In order to reduce the associated impacts with this assembly, KieranTimberlake introduced a perforated patterning to the metal accent panels, reducing the quantity of metal used in those panels by almost half.
Matthew Millman
KieranTimberlake also detailed the frequency and location of fasteners in the
C O N TA C T
and the corrugated steel at the back of the rainscreen.
panels to allow a lighter gauge of steel to be used for both the accent panels
Efrie Escott KieranTimberlake 841 North American Street Philadelphia, PA 19123 (215) 922-6600 efriedlander@kierantimberlake.com C A S E S T U D Y University of Washington North Campus Housing
KieranTimberlake
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