Our modular Passive House is under construction

This week Beracah Homes in Greenwood, Delaware began construction of our — and their — first modular Passive House. The house is sponsored by the Housing Initiative Partnership(HIP), a Maryland non-profit organization committed to providing affordable housing. HIP had seen the Habitat Passive House at the last DC Solar Decathalon and had toured our Bethesda Passive House, and procured a grant to build their first one. We teamed up with O’Neill Development, our partner on the Bethesda project and Beracah to offer a modular Passive House. The factory construction will be complete in two weeks, and site installation and finishing work will begin immediately.

Our approach to the project was simple: let a good modular builder do what he does best, building as much of the house as we can in his shop. Then add additional insulation, complete air sealing, and add the HVAC system in the field.

Beracah was already doing Energy Star certified homes, using densepack fiberglass for wall insulation, the Huber Zipwall system for an air/water membrane, and committed to upping their game in the modular market. Their enthusiasm for taking on the house was in marked contrast to the attitude of most modular manufacturers we spoke with.

The project has involved a lot of careful planning. We had to learn the rules of the road in their construction system — very different from the site-built and panelized construction we are used to. And they had to learn about all the specialized requirements for thermal bridging, air sealing and ventiliation that go with Passive House construction.

From the beginning we have worked with their senior construction specialist, John Meredith, who has tirelessly stuck with us to iron out the myriad construction issues. And now the rubber meets the road.

To keep things as simple as possible (remember this is our first!) and to keep costs under control, we decided at the very start to build the house as two modules that would be stacked on top of each other. Field work joining modules together adds time and money and the potential for greater air infiltration, so the fewer the modules the fewer the problems. We designed the house (1600 sf, 3 bedroom/2-1/2 baths) with all public spaces in a rather open-plan first floor, and all private spaces on the second floor. Making that happen within the 18′ maximum allowable exterior dimension was the challenge.

Framing was completed on both modules last week. Next week will be devoted to roughing in plumbing, electrial, and mechanicals. Below are some pictures of the progress this week.

Beracah front facadeBeracah’s headquarters in Greenwood Delaware.

Beracah shop exteriorOut back where the work gets done.

modular passive house The first floor module – note Huber Zipwll system at exterior, standard with Beracah Homes.

Modular passive house framingFirst floor module interior. Note taping of subfloor (Profil’s Tescon Vanna tape).

Modular passive houseInterior corner — note double wall construction and space left at corner to allow densepacking there. The 2×6 ceiling framing is standard with modular construction, holding the module together during shipment and providing extra space for running conduit and pipes. Note the header at the left — headers generally have 2x’s at interior and exterior with the interior filled solid with rigid foam.

modular passive house constructionSecond floor platform. Ready for construction of exterior walls, which happens right on top of it.

Modular passive house exterior wall constructionTaping of the second floor walls using Huber Zipwall system.

Modular passive houseDetail of second floor wall and platform before tilt-up of wall. Sill sealer is not necessary, as our air barrier is at the exterior wall sheathing.

Tilting up the wall!

IMG_3610Framing up interior partition walls of second floor module.