What's Green, Affordable, and Buildable? Interview with Bryn Davidson of Lanefab Design/Build
If you follow “Passive House twitter”, you’ve probably seen the insightful tweets and SketchUp animations posted by Bryn Davidson, Passive House practitioner from Vancouver, BC, and owner of Lanefab Design/Build. After enjoying one of those animations awhile back, I had the chance to catch up with Bryn to interview him about his approach to projects, his latest Passive House assembly thinking, and how he situates Passive House performance, embodied carbon, and urban design in relationship to climate change and action. Enjoy!
Bryn Davidson: For our single family Passive House projects, we’re typically doing a 17-inch thick wall, and we’re usually aiming for around R‑52 effective in the wall and anywhere from R‑70 to maybe R‑90 in the roof. So, they’re quite thick assemblies. One of the biggest challenges you have with Passive House is achieving a high level of air tightness. You have to look at how your air barrier is contiguous from where the wall meets something like the roof, but also plan the sequence of how it all goes together. That’s why I like doing these sketch-up assembly models because we can get a good sense of, as the guys are actually onsite putting this together, what is the sequence and whether there’s anything weird that you have to be on top of ahead of time. Sometimes in the Passive House world we call it the flappy bits, the little bits of membrane or something that you have to put in early so that you can connect layers later.
For years, we have been using SIP (Structural Insulated Panels), building a two-part wall with SIPs. That’s where the “fab” in Lanefab comes from. We’ve been pretty happy with this approach because we can build a thick-wall project for a cost that’s not that much different from what other builders are doing at code minimum. Our goal has always been to do it on a cost-competitive basis, so we can do a green building on every single project as opposed to doing one “uber-green” project and nine code minimum ones.
So our strategy has always been to figure out not just what’s green, but also what’s affordable and what’s buildable. That’s part of our ethos, and we’ve been able to do that pretty well with SIP panels for a lot of years. Now, going forward, as we get more used to delivering Passive House projects, we start looking at things like embodied energy and some of these second order things that are maybe not as compelling for the typical client, but are an important part of the overall discussion. A few years back I did a TEDx talk about doing net positive projects in the context of climate change. After you’ve done Passive House and after you’ve done walkable infill and you’ve avoided building on greenfield sites, and all those things, the next big step is to look at reducing embodied energy.