Bayside Anchor: Huddle Together for Warmth

Case Study of a Passive House Apartment Building

Presented by Jesse Thompson, Kaplan Thompson Architects, Portland, ME

Our office is currently designing several mid-rise PHIUS+ or Passive House apartment buildings. These buildings range from 20 to 45 units, have mixed use ground floors and are typically in established neighborhoods. These projects are very exciting for our office because they are built under very tight cost constraints but have enormous opportunity to produce Passive House projects for minimal cost increases over conventional buildings while providing owners with massive operational savings.
The building enclosures and mechanical systems of these buildings are very different from single family or townhouse Passive House projects. They have lower insulation values than those other project types, often within the range of typical mass-market construction, but their performance depends much more heavily on air sealing, highly efficient ventilation systems and smart glazing selection.
In our presentation we will discuss the design trade-offs we have learned, the available equipment we have been specifying, and talk about where the industry needs to go to make these buildings commonplace across the country.

We will focus on the Bayside Anchor, a 45 unit low-income apartment building in Portland, ME which was completed in Dec 2016 after a fast 10 month construction period. It is designed by our office for the Portland Housing Authority and was a national competition winner by Deutche Bank called “Lowering the Cost of Housing”. It will be PHIUS+ Certified.

The project uses conventional commodity construction systems for our local market: panelized double stud wall construction. Roof assemblies is a truss roofs with low-slope membrane roofs with rigid insulation. Exterior wall R-values are typically in the R-35 range, roof assemblies in the R-60 range, neither of which are far out of range for conventional construction in today’s multi- family market in the Northeast. Both project have advanced air-sealing which is atypical for the building type, perhaps 5x higher quality than the typical values expected in the market (0.05 CFM50 / SF of shell compared to the typical 0.25 CFM50 / SF shell area).
The windows are triple glazed, but the specification requires tough, easy to maintain products and long lead times are problematic from a project funding perspective, so they often use north American fiberglass  or vinyl window frame units.

These buildings are managed rental projects, which mandate centralized ventilation systems with minimal maintenance requirements, differing from typical condominium project types where mechanical systems can be distributed on a unit-by-unit basis. Ventilation systems in our multi-family projects are typically neither single apartment or whole building units, instead we try to gang 5 – 6 apartments onto mid-size ERVs in the 300 – 500 CFM range, allowing short duct runs, no vertical shaft construction, and fairly easy maintenance.

Heating systems are a challenge in our area. Typical local systems are gas fired hydronic baseboards systems, and heat pumps are still expensive compared to other markets, with pricing in the $8,000 – $9,000 per apartment range. This has steered several local low energy projects towards electric resistance heating, with accompanying high Primary Energy consumption problems.

About Jesse Thompson

Jesse is a partner at Kaplan Thompson Architects in Portland, Maine. He grew up in the Northeast Kingdom of Vermont, and lives in the Deering Center neighborhood of Portland with his family. He received his BArch from the University of Oregon in 1996. He is a Maine Licensed Architect (NCARB), a board member of Maine AIA and the Portland Society for Architecture, a LEED Accredited Professional and the first architect in northern New England to become a Certified Passive House Consultant.