Laura Ours, AIA, Kevin Walker, AIA, and Nathan Webb, AIA, with Longhouse Architects sat down virtually with David Peabody, FAIA, and Robin McGrew, AIA, of Peabody|Fine Architects to learn about their path in sustainable architecture. David was an early adopter of the Passive House (PH) methodology; he’s been a Certified Passive House Consultant since 2009. Robin is also a CPHC and resides in a Passive House that she designed and built in 2019.
Longhouse: Robin, how is it to live in your Passive House?
McGrew of Peabody|Fine: Really comfortable. Having experienced all the seasons, I have been amazed at just how constant the temperature stays. And the indoor air quality is great. I know there’s fresh air coming in, in a controlled way. I see everything that’s filtered out when changing the filters.
Longhouse: As a firm, how did you settle on Passive House as your sustainability metric?
Peabody: It was an accessible way to quantify what we were doing as we made decisions on energy efficiency upgrades. Rather than a prescriptive method, the software is very useful for allowing the architect to balance tradeoffs. The modeling allows for feedback of design options in real time. It was too cumbersome to pay engineers and wait for their feedback. Also, PH goes about achieving energy efficiency, not by fancy, expensive mechanical systems, but by a super tight, super insulated envelope. This puts things in the architect’s control and makes for a more affordable way to get closer to net-zero building. We also valued that the Passive approach is grounded in extremely good building science, which lowered the risk as we moved into new territory in energy-efficient buildings
Longhouse: With Passive House originating in Germany, how does it translate to our Virginia climate?
Peabody and McGrew: Passive House Institute US (PHIUS) has different metrics for the different US climate zones. This is really important in Virginia’s challenging climate with both extreme heat and humidity as well as cold temperatures. In the training, you learn approaches to minimize thermal bridging and look out for vapor drive. Minimizing thermal bridging is important because cold spots can mean a place for condensation, and it will improve the overall insulation efficiency for the envelope.
Longhouse: How do you get clients to buy into the idea of Passive House?
Peabody: There are three benefits we share with clients.
1. Energy savings: on average a Passive House has only 7% more upfront cost, so you can cut emissions and the monetary pay back is not so far off.
2. Comfort and health: the temperature is very constant, with no drafts or stratification, and, with continuous filtered ventilation, the indoor air quality is very high. These are very appealing to clients.
3. Resiliency: if you lose power the house can stay at temp for several days, in wintertime dropping roughly a degree a day, without ever diving into battery backups and the like.
Longhouse: What do you see as the hurdles keeping more people from building this way?
Peabody: The building industry’s resistance to change. It’s new, it sounds foreign, and why bother with it when you are fat and happy doing business as usual. But, when incentivized, that attitude can change. For example, in Pennsylvania, a program offered points toward Low Income Housing Tax Credits for projects meeting Passive House standards. And, now developers there are building Passive Houses at the same cost as standard construction.
Longhouse: And, it means low utility bills for the residents!
Longhouse: Do you have certain builders you work with?
Peabody and McGrew:: Finding good builders is tough. But it doesn’t take a specialized builder, just a good builder, who is willing to think and learn new methods. And most good builders enjoy that challenge. We’ve found it’s important to have the builder involved early on and have them buy into the ideas and work through the detailing with us. That is the way we did our first one; the builder and I basically figured it out together. Now, as opposed to then, PHIUS offers a training course and certification just for builders.
Longhouse: How many people in a firm would it make sense to be PH certified?
Peabody and McGrew: The Passive House training is really useful for multiple members of the firm, though not a requirement. In our firm all project managers are PH certified. One of us has become very adept at using the modeling software. Passive Building 101 on the phius.org website is a good intro. The next step would be for one person to take the training for certification.
Longhouse: How do you work the mechanical design of the houses?
Peabody and McGrew: Early on we typically just worked with the mechanical subcontractor. But, now we usually hire a mechanical engineer who specializes in low-load buildings. And, we’ve been including dehumidification as part of the mechanical system. Even though the small variable speed heat pumps we use can run nearly constantly, with the lower cooling demand they are taking less humidity out of the air, so we’ve been adding dehumidification as a precaution.
Longhouse: Do your clients sometimes opt for PH principles without the PH certification?
Peabody and McGrew: They do, but we encourage them to go through the process of certification. Not for the gold star, but for the added layer of observation during construction. To have another set of eyes reviewing details and seeing them built in the field is really useful. Having two rounds of blower door testing and thermal imaging are great tools to aid in quality construction as well. The certification cost is roughly $6500 in certification and architectural fees. But we think it’s worth the investment, and good insurance for the owner that they are getting the best product they can.
Longhouse: Does Passive House have systems to measure embodied carbon?
Peabody and McGrew: Not at this time, but they’ve been talking about adding that in. It is hard to make it a standard, because it is so difficult to calculate and track. As a firm, we make strategic choices in material selections. We limit our use of concrete. We chose insulations carefully. What is the point of using an insulation material with great R-value, if it takes 70 years of energy savings to offset the greenhouse gas emissions associated with making it?
Longhouse: Anything else you’d like to share with other architects?
Peabody: As we all know, buildings are responsible for roughly 40% of greenhouse gas emissions. If we are planning on cutting emissions by 50% by 2030 to keep this planet livable, architects have got to act. This is the future of building. So why not embrace it? Why not be ahead of the curve? Virginia energy codes are lagging behind D.C. and Maryland. But we don’t need to wait for the code to require us to do this. It’s not that difficult. It can just be the way we do it. I urge all architects to go to the Architecture2030 and the phius.org websites and get involved.