Four-inch-thick foam board provides R-20 insulation under and around the edges of the radiant floor slab (left), which is tinted chocolate brown to serve as the finished floor. The inside 2x4 wall of the 11 1/4-inchthick double framing will cover the exposed foam around the perimeter (right).
Tripleglazed windows cost up to 50 percent more than comparable doubleglazed units but — according to computer modeling — will represent a 20 percent gain over doublepane glazing in the building’s energy performance.
Single-stud corners reduce thermal bridging and allow fuller insulation coverage. Wall plates running parallel to the ceiling joists are nailed to 1x3 ceiling strapping, eliminating redundant framing.
The bottom plates of the inside walls sit directly atop the slab’s perimeter insulation, preventing a direct mechanical connection to the concrete. To hold the walls parallel to the exterior walls, the author used plywood standoffs and sealed beneath the plates with expanding foam.
To allow the main entry door to open more fully in the thick exterior wall, the author widened the inside rough opening and applied rigid insulation to the inner face of the exterior wall studs, then sealed all seams with expanding foam.
Ties made from Zip sheathing scraps connect 2x3 extensions to the 2x10 rafters to create a 14-inchdeep insulation cavity.
Gable walls are framed with double top plates in lieu of end rafters, breaking conductivity through framing members and creating an unobstructed insulation cavity.
Blower-door testing at the weathertight stage is effective for early detection and treatment of air leaks in the envelope. The author achieved remarkable levels for this stage of construction.
Triple-ply Par/Pac membrane is stretched around framing edges and rigorously stapled to prevent the cellulose insulation from bulging past the wall plane. Cellulose is blown through slits in the membrane to a density of 3.5 pounds per cubic foot. The slits are then resealed with tape.
An energy recovery ventilator (ERV) provides whole-house ventilation while capturing heat held in humid indoor air and transferring it to the incoming fresh air.