The house uses raised-heel roof trusses to allow for 18″ of blown-in cellulose above the second floor ceiling. For maximum effectiveness, that insulation has to extend to the outside edge of the four-inches of R-Max foam board that will be attached to the exterior of the long sides of the house (the gable ends will be handled differently and discussed later). Regardless of what we used to contain the insulation at the outer edges, we knew that it would be easier to install before we installed the Zip sheathing on the second floor ceiling.
Our initially thought was to use insulation netting as a baffle to contain that insulation at those two outside edges. But after giving it some thought, and discussing it with an insulation sub, that idea didn’t seem ideal. We felt that the netting would be too unstructured; potentially allowing insulation to interfere with the soffit vents and the flow of air to the ridge vent. That same quality would also make it difficult to install properly, as it would have to drop down between each of the 2×4 truss members. So we settled on an alternative using OSB and some 2×6 blocking.
The OSB, ripped into two-foot-wide strips makes up the exterior baffle. The 2×6’s were stood on edge and placed between each of the 2×4 truss members to a) complete the baffle between the truss members and b) create a backer that the lower edge of the OSB baffle could be nailed to. The top edge of the OSB was then tacked into the truss members that formed the roof line. While it may be a bit difficult to picture after reading, it was fairly inexpensive and easy to execute. It took five sheets of OSB and ten 2×6’s.
Here are some photos that show the different elements and perspectives:
Here you can see the 2×6’s that were attached between the truss members, above the 2nd floor ceiling:
In this photo you can see the two-foot wide strips of OSB tacked in place to the 2×6’s (at the lower edge) and the roof members of the truss (at the upper edge):
The gap that you see between the 2×6’s and the ceiling in the photos above and below is 3.5″ wide. The bottom of that gap will be covered by the 4″ of foam board that will be attached to the outside wall. So, in effect, the top edge of the foam boards, which will run along the bottom edge of the truss members, will complete the floor for the attic insulation.
The first blower door test is now history. Results came in at approximately .17 air changes per hour @ 50 Pascals, well below the Passive House requirement of .6 ach @ 50 Pascals. Here are a couple of photos from the test:
The reading (in cubic feet per minute) actually fluctuated between the high 40’s and high 60’s at roughly 50 Pascals (the photo above is showing 49.9 cubic feet per minute @ 51 Pascals). Although the house contains approximately 29,000 cubic feet of interior space (when including the basement), the Passive House rating system uses an adjusted cubic feet computation, which reduces the total to approximately 23,600 cubic feet (only 60% of the basement is counted) and makes the target standard more difficult to attain. Had we been able to use the entire 29,000 cubic feet in the computation, the test results would have been lower yet.
The roof is complete. I initially intended on using Certainteed Landmark Solaris shingles. It’s a “solar reflective” asphalt shingle that claims to reduce roof temperatures by up to 20%, according to the company. But at approximately $190/square, it was pretty pricy. So we ended up using Certainteed’s Landmark Pro, which appears to be essentially the same, but without the reflective coating. The cost was about $96/square.
Installation of the septic system was completed several weeks ago. As mentioned in one of the early posts, it’s about the only thing that one can get easily approved on a steep slope. Two 5’x70’x3′ trenches, a two-stage 1,250 gallon tank, and a distribution box:
The steep slope (and well-perking soil) proved helpful. No pump required. Just let gravity do it’s job.
This week, we got started on the garage. The footings were dug on Monday, and poured on Tuesday. Then the electrician, Gene Huber, of Huber Electric here in West Chester, took over. On extremely short notice, he juggled his schedule, came in and installed the conduit. I didn’t want a meter hanging off the side of the house, so we’re going to put it on the north side of the garage (which is closest to the transformer). We’ll then have a 200 amp panel in the first garage, a 200 amp panel in the house (along with a generator transfer switch), and a 100 amp panel in the second garage (when it is eventually built). So, from the first garage, we ran a 3″ conduit to provide power to the house, a 3/4″ conduit for an indoor house switch that will control the exterior garage lights, a 1″ conduit that will allow us to plug a portable generator into a receptacle in the garage (rather than having it up against the house) and a second one-inch conduit that will make it easy to run a Comcast line to the house, should we get fed up with Verizon Fios. Finally, a two-inch line was laid from the to-be-installed panel in the first garage to the south side of the driveway, in position for a future run to the second garage, which will be on the east end of the lot. Everything in the same trench:
The garage foundation was completed on Friday: