The Passive House Pursuit

Making Affordable Housing More Affordable
By CORDELIA PITMAN

In May, 2016, Village Centre Apartments in Brewer, Maine opened its doors to city- and state-wide applause. Located just five minutes from downtown Bangor, Maine’s second-largest city, Village Centre provided the metro area 48 units of much-needed workforce housing and is one of North America’s largest Passive House developments to date.

Already popular in Germany where it originated, Passive House is a rigorous, voluntary standard used to attain energy efficiency, thermal comfort, quiet living conditions and excellent indoor air quality.

Wright-Ryan is currently working toward a late fall 2016 completion on Bayside Anchor, a similar 45-unit development by the Portland Housing Authority and Avesta Housing in Portland, Maine and designed by Kaplan Thompson Architects, which is also pursuing the PHIUS certification. Both projects are proof of an encouraging trend that is emerging as Passive House continues to make in-roads in commercial development – the design and building standard is making affordable housing more affordable. The benefits for both residents and building owners are numerous.

First, the application of Passive House design and construction principles means lower operating costs for building owners, supporting long-term viability of properties. Village Centre is estimated to be over 60 percent more energy efficient than a code building, with a targeted site energy use intensity of 22 kBtu/sf/yr. And these are simply the results that can be achieved within the fixed budget (roughly $139 square feet) defined by the project requirements as a publicly funded development under the Maine State Housing Authority. Many cases demonstrate that Passive House buildings can offer energy savings from 75 percent up to 90 percent when compared with average new buildings or typical building stock.

The benefits for residents and other end-users, chiefly comfort and energy efficiency, are even more important. In many cases, the energy savings realized by building owners may be passed on to tenants. An extremely tight building envelope (0.05 CFM50/ft2 allowable limit for air tightness) and no thermal bridging means steady, consistent thermal comfort year-round. In addition to maintaining pleasant temperatures, triple-glazed windows and highly-insulated exterior walls and interior partitions provide sound reduction benefits for quiet living conditions. Ventilation systems supply a constant source of fresh air for improved indoor air quality.

Passive House projects require collaborative, innovative approaches and the application of the latest design tools and techniques to achieve aggressive goals. Wright-Ryan found that the Construction Manager at-Risk (CM at-Risk) method of project delivery made for a far more collaborative job and increased control with sub-contractors than a standard Design-Bid-Build method, making it well-suited to tackle complex projects of this nature. CM at-Risk offers clients and project teams the benefit of collaborating with a qualified, knowledgeable builder from the project’s earliest stages, often during or prior-to conceptual design, for informed decisions and strategic guidance related to difficult cost-benefit choices. For instance, the integrated and iterative design method during the pre-construction phase of the Village Centre Apartments project established a cooperative team culture, with Wright-Ryan’s estimating analysis and pricing models informing design details like wall systems, insulation, and windows.

The result was an extremely airtight structure. Focusing on the quality of the building envelope and reducing thermal bridging as much as possible further allowed the team to significantly downsize the HVAC systems. The team analyzed nearly 10 different HVAC systems for design and cost benefits. The final package selected was comprised primarily of highly-efficient Energy Recovery Ventilation Units (ERVs) which allow the heat contained in the exhaust air to be re-used. Some electric baseboard units were also included for supplemental heat. Village Centre also takes advantage of solar heat gain, through strategic building siting, and internal heat gain to reduce dependence on the limited systems. In addition, glazing is tuned to solar exposure and the project made use of solar shading.

Progressive techniques are also necessary when the time comes to execute in the field. For both Bayside Anchor and Village Centre, Wright-Ryan stressed the importance of maintaining the integrity of the buildings’ air barriers to all subcontractors. A comprehensive schedule of air-sealing and caulking details were developed to support this effort. Very low air-leakage rates at Village Centre show that these efforts pay off. Lean Construction methods, such as “Batching Plans” for efficient sequencing of trades from floor to floor, were also used to drive the schedule and ensure buy-in and collaboration with subcontractors.

In the end, our chief estimator (initially the biggest skeptic of the additional investment Passive House would represent) summed it up when Village Centre opened its doors: “Why aren’t we using these standards for all of our projects!?” In construction, where the lowest bid often rules, it can be easy to lose the value in the aggregate dollar amount. What gets lost though, is the human element of the Passive House standard, which places comfort and environment at the center of its principles.

Cordelia Pitman is the Director of Preconstruction Services at Wright-Ryan Construction. To learn more, visit www.wright-ryan.com.