Black EPDM Roofing Helps Multifamily Buildings Achieve the Passive House Standard

Garnering Attention

A 60-mil EPDM membrane was installed on all three buildings.

A 60-mil EPDM membrane was installed on all three buildings.

The owner of Weinberg Commons, Washington-based Transitional Housing Corp. (THC), a non-profit whose goal is to end family homelessness by 2020, recognized there would be upfront hard and soft costs. Hindle asserts Passive House buildings pay back a good ROI. However, THC’s primary motivation to undertake PH was not economic. It was to provide more stable, resilient, comfortable housing options for low-income families. The owner’s representatives believed retrofitting all three buildings rather than just one would allow them to help 36 families rather than just 12 for only a marginal upfront cost increase. In fact, traditionally, the cost increase for a Passive House retrofit is between 10 and 20 percent. For Weinberg Commons, it was 12 percent above typical gut-renovation construction.

In November 2015, Weinberg Commons was one of the stops on a tour of innovative housing, sponsored by Greenbuild International Conference and Expo, which is dedicated to green building. Fine addressed the group of 50 designers who were on the sold- out tour, and Thomas W. Hutchinson, AIA, FRCI, RRC, CSI, RRP, principal of the Hutchinson Design Group, Barrington, Ill., and a Roofing editorial advisor, gave the group an expanded view of the environmental benefits provided by the EPDM roofing membrane, including a 45-year track record of performance in the Washington area and in similar climates.

Hutchinson pointed out the essence of sustainability for any building product is long-term service life. EPDM—based on empirical evidence and rigorous scientific testing—has a service life of 40 years. This means that beyond the day- in, day-out energy efficiency provided by the roof system, no energy will be expended for removing and replacing the roof until well past the mid-century mark. In fact, EPDM has a 45-year track record of performance in the Washington area and in similar climates.

Hutchinson also underscored that energy costs are expected to rise yearly, and the return on the upfront investment in a Passive House will rise along with those energy costs. This could contribute to better and more financing opportunities for Passive House projects.
Now that the construction phase is over, Weinberg Commons has achieved its most important goal: providing affordable housing for low-income and formerly homeless families. Washington, D.C., has a severe shortage of low-in- come housing. This project is a successful example of reusing building stock, maintaining current communities while raising the standard of what affordable housing can be. “I had countless passersby ask me when the condos would be finished,” Fine notes. “The public perception is that any radically new and different construction means ‘in with the haves and out with the have-nots’. This project breaks that pattern.”

Photos: Zavos Architecture & Design

PH Certification and Considering Net Zero

Hindle worked with Fine to design the air-sealing and insulation strategies for the buildings. Hindle says just one building was certified because the project was essentially a first-of-its kind. “It was understood that PH construction would be a new experience for all and there might be some trial and error or learning along the way,” Hindle says. “This is particularly true of the very rigorous airtightness standard. Building to that standard—more than three times tighter than EnergyStar v.3—in a retrofit scenario was bound to be challenging, and there were no guarantees that it would work.” He agreed with Fine’s approach to use the education from buildings A and B to ensure Building C would meet Passive House standards.

Hindle also points out an additional factor in selecting just one building as a candidate for PH certification: “Given the very difficult orientation of the buildings, we were not sure how difficult it would be to make all three buildings Passive House.” Hindle and Fine made the decision to pursue certification on the building they were most confident would succeed. Again, that was Building C, which had the best—though not ideal—orientation to the sun.

The cost of Passive House certification is very reasonable and was not a barrier to certifying all three. However, third-party verification and testing to achieve PH status can be a substantial additional cost. Potential modeling and design revisions also can be costly had all three buildings not met the standard using the same envelope and HVAC strategies. Though Hindle and Fine are confident all three could now meet PH standards, that was not known at the outset of the project.

Why did the architects use the Passive House approach rather than focus on achieving Net Zero energy use? Fine says although Net Zero building and Passive House construction are frequently confused or intermingled, they are, in fact, different. A passive house looks at the physical manifestation of the building, literally the envelope and the mechanics inside. “So it’s the insulation levels, it’s the thermal bridge reductions, it’s the air tightness, it’s the efficiency of the systems. The philosophy is that basically from the baseline there’s no waste of energy.”

Fine says this differs from the Net Zero approach “ … because many Net Zero projects are not necessarily concerned about energy reduction or use. They are more concerned about offsetting their excess consumption with their own energy generation.” Fine says this is an important distinction because “ … We cannot solve the energy puzzle without us as consumers modifying our behavior. PH proves this, in that when you see design firms and contractors modifying their behavior, process and product, true reduction is achieved. Consumers, homeowners, renters need to participate in this, too. Use less energy, use less water, period. Enable the reduction by building better envelopes from the start.”

An important first step in overcoming these challenges is to secure buy-in from all the players: The owner needs to understand that, compared to a standard retrofit, this is a different type of project and a different type of process from the design to closeout. Likewise, having the architect and builder at the table very early in the process will reduce the chances of redesign during the process. And, ideally, it’s important to find a contractor with personnel who are familiar with the skills needed in Passive House construction. Hindle says, “What is required is an understanding of the five principles and how they are being achieved in a given design.”

Builders who take on a Passive House Project will need to work with the designers to determine the most effective means of applying the design solutions in terms of feasibility, cost effectiveness, order of operations of the construction of individual assemblies and connections, and sequencing of the workflow of the project as a whole so that crucial details are not missed. The builder needs to have a level of attention to detail and craftsmanship throughout the building and at all stages of construction. “It is a bit like having a finish carpenter’s attention to the finest detail from the first day of foundation work,” Hindle notes.

MATERIALS

EPDM membrane: Carlisle Syntec Systems
Polyiso roof insulation: Hunter Panels and Atlas Roofing Corp.
Airtight membrane and weather-resistant barrier: Solitex Mento Plus WRB by Pro Clima
Outboard wall insulation: Spider Dense Pack Blown Fiberglass Insulation from Johns Manville
Vertical fiber-cement siding: Nichiha Illumination Series
Energy-recovery ventilator: UltimateAir 200DX RecoupAerator
Vertical air handlers and condensing units: LG Multi V VRF
Extrusion windows: Yaro Economy+ Schuco PVCU
Foundation insulation: Roxul Drainboard stone wool
Window overinsulation: Roxul Cavityrock and Rockboard
Basement vapor barrier: Cosella Dorken Delta-MS and -FL
Crawlspace vapor barrier: Stego Wrap Vapor Barrier, 15 mil

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About Louisa Hart

Louisa Hart is communications director for the EPDM Roofing Association, Bethesda, Md.

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