August 31, 2023

Setting a new sustainability standard for affordable housing

Bicknell

Reddy

Explosive growth. Unprecedented housing inequity. Climate change. How can King County address all three?

Navigating the delicate balance between energy efficiency, sustainability and cost containment is a challenge faced by many multifamily developers. This tension is even more pronounced for affordable housing owners who are working to deliver high quality, resource-efficient buildings within limited capital and operating budgets.

In 2018, the Housing Development Consortium of Seattle-King County (HDC) established the Exemplary Buildings Program to provide financial support and technical guidance to affordable housing owners looking to pursue an ultra-efficient building standard while still delivering as many homes as possible at reduced rent levels.

The goal of the Exemplary Buildings Program is to improve performance above code, and to document lessons learned to help inform future projects to normalize a cost-effective, high-performance standard for affordable housing. The program has been successful in helping affordable owners prepare for the energy code changes that took effect in 2021 as well as the forthcoming updates that are scheduled for later this year.

Partners and projects

Building design and performance experts, including O’Brien360, Ecotope, Coughlin Porter Lundeen, DCI and 4EA Building Science, have developed best practice guidelines around building ventilation, domestic hot water heating, solar energy, and exterior wall assemblies. Seattle City Light was also a key partner in launching the program, and providing significant financial incentives and technical support to affordable housing owners.

Photo courtesy of Marpac Construction [enlarge]

Project teams collaborated early on design and product choices to ensure buildings like Sawara in Yesler Terrace are air-tight and weather-resilient.

The Exemplary Buildings Program has five initial demonstration projects — four projects in Seattle and one in Bothell — creating over 500 new affordable homes to address our region’s need for affordable housing. Each of these owners are motivated to create better living environments for their residents, ranging from individuals coming out of homelessness, families with children and seniors, while reducing the long-term environmental impacts of their buildings.

These demonstration projects made an initial commitment with Seattle City Light and HDC to design their buildings to a performance standard of 20 EUI (Energy Use Index), or 40% less energy than the 2015 Washington State Energy Code (WSEC), or a Passive House (PHIUS) standard. The average EUI for new affordable multifamily buildings in the past decade has been between 30 to 35 EUI. Imagine Housing’s Samma project and DESC’s Hobson Place project also participated in the State’s Ultra High Energy Efficiency program, which provided additional financial support to construct to the PHIUS building standard.

Information courtesy of Walsh construction [enlarge]

Challenges and lessons learned

All five projects shifted to 100% all-electric building systems — a significant leap from a design and operations perspective. An important component of making this leap was utilizing heat pumps to generate hot water for all of the apartments. Heat pumps are significantly more energy efficient than natural gas and electric water heaters.

Another new system incorporated into all the buildings is balanced ventilation with heat recovery for apartment ventilation. These systems provide reliable, filtered air to the apartment, while also reducing energy use by recovering the energy of air exhausted from the building to heat incoming air. Each building incorporates different ventilation designs, both centralized and in-unit, enabling the EBP to disseminate the design and construction benefits and challenges of each approach.

At the time the demonstration projects started design, these high-efficiency technologies were uncommon in housing developments. It is risky for affordable housing owners to commit to new technologies. However, the technical assistance developed by the EBP program helped guide decision-making, and the lessons learned have been invaluable as the 2018 and 2021 energy codes have rolled out with new requirements to incorporate these new technologies.

In addition to enhanced building systems, building envelope performance has been critical to hitting the proposed Exemplary Building performance target. It was crucial for project teams to collaborate early on the design detailing and product choices for the roof, exterior walls, windows, and other details to ensure these buildings are air-tight and weather-resilient. This diligent coordination paid off for the DESC Hobson Place South project, which met the Passive House air-tightness standard of 0.08 cfm/ft2, over 60 percent better than the code-required 0.25 cfm/ft2.

What’s ahead?

As the remaining four projects finish construction, HDC and SCL will continue to aggregate final design and cost information and monitor projects through their initial occupancy periods. The 2018 energy code and forthcoming 2021 code update are now requiring many of the “exemplary” features incentivized by the initial phase of the EBP program. HDC will therefore evolve its best practice guidelines for pursuing a high-level of energy efficiency, carbon reduction, and healthy product selection with a long-term goal of supporting owners who want to pursue a net-zero energy standard.

HDC is also working to develop standards for retrofitting existing buildings to improve performance and reduce carbon emissions. They continue to convene industry experts and public agencies to provide technical and financial support to owners in their efforts to update multi-family buildings to prepare for compliance with local and state Building Performance Standards. HDC’s Decarbonize Affordable Housing Now initiative will expand the Exemplary Buildings program to support owners in their goals to comprehensively retrofit and decarbonize existing buildings across owner portfolios.

Becky Bicknell is the client relationship manager for Walsh Construction Co.

David Reddy is the principal of O’Brien360’s building performance group.

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