Progress on Net Zero Home in Fairfax
Weather has been a killer, but we are finally out of the ground, and framing lumber is onsite and ready to go up. This spring has had the longest stretch of rainy days since the 1880’s, which has been great for my garden and our trees, but not so good for excavation and the pouring of concrete. Here are photos of progress to date..
The site, cleared and with excavation equipment ready.
Excavation work in progress.
A dry day with footings in place. On this project we used our standard high density eps foam footings over a mudslab. At sides and top of footings, however, we used 2 layers of 2″ Roxul Comfortbat CIS mineral wool.
Note the waviness of the sides of the footings. We used rebar set into the ground to hold the side insulation in place to work as our formwork. Whereas a foam would have withstood the pressure, the mineral wool, less stiff, gave way to the pressure.
The mineral wool did not stand up well to the setting up and taking down of forms. Much was knocked loose and abraded. We had to come back later and replace some, and fill gaps with canned foam. This is an example of the damage.
Foam enclosure around sump crock. Where before we had a circular piece of foam made up to wrap the crock, we found it easier to make a simple box and then fill in with gravel behind after setting crock.
A mountain of 4″ EPS foam waiting to go under the slab. Our intention was to use Roxul Comfortbats, which have a much lower global warming potential (GWP). While it has been widely used under slabs in Canada and Europe, because Roxul has not produced an ICC report for that application the city wouldn’t allow it. We resorted to the foam we have used on our past PH projects.
The entire underground insulation and wall drainage system is being installed by Aird, Inc. The also did the Sto EIFS system on our Rockville passive house. Rob Aird has been a great partner in the planning and construction of these houses. Here the Aird crew is installing the second 2″ layer of the Comfortbats. Note the staggering of the joints to prevent air gaps that would reduce thermal performance. Notice also all the cans of glue and adhesives lying on the ground. This stuff is hard to hold in place and doesn’t adhere well to much of anything. In the end they used Liquid Nails to adhere to the Carlisle MiraSeal and Carlisle Hardcast Travel Tack spray adhesive to adhere the two layers of insulation.