Specific Insulation for Specific Locations
From the foundation pour to the attic floor, insulation is a key component of the FHB House and any high-performance house.
On the one hand, achieving the high R-values needed to make a cold-climate house energy-efficient is easy. Insulation is a material and if you put enough of it in a house, you’ll meet the target R-value. Of course thermal performance is only one part of the equation. High-performance houses also need to be air-tight, comfortable, healthy, and more. And insulating materials differ in many more ways than R-value alone. There’s a range of cost, air, and vapor permeability, global warming and off-gassing potential, among many common insulators. The FHB House team chose four different insulation types to meet their performance goals.
The foundation was formed with Amvic insulating concrete forms (ICFs). The ICFs are made with EPS rigid foam and 100% recycled polypropylene webs providing both the forma and insulation for the FHB House’s basement walls.
A mountain of Roxul Comfort Board insulated sheathing panels were delivered to the site during the framing stage of the build. The 2-in.-thick panels are vapor open allowing them to get wet and dry to the outside which is important because they are to be installed on the outside of the house.
The Roxul insulation panels are applied to the second-floor walls before the walls are raised and are held to the house with furring strips and structural screws. The furring strips create a drainage and air space behind the siding allowing the insulation and siding to dry easily.
The wall cavities are insulated with fiberglass batts from CertainTeed. The R21 Smart Batts are 5 1/2 in. thick for 2×6 walls. The facing is a vapor-variable which means that it allows vapor to pass when humidity is low and becomes more impermeable as relative humidity rises.
The attic floor has 22 in. of blown fiberglass. Because the air barrier is at the second floor ceiling and the roof is vented, this cost-effective insulation makes the most sense for the FHB House.
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