While the house gets set down on the new foundation and framing continues, we’re already preparing to insulate and clad the home. One of the key objectives of Highland is to build a home that is significantly better insulated and more airtight than a code-built home. In our case, we’ve decided to combine both interior and exterior insulation. One of the GC’s lead carpenters, Tom, is building some sample wall mockups so we can get the details right, and while we’re at it we’re also building a few “code-built” mockups for comparison. Not complete yet but you can see the differences already:
Code-built (left): fiberglass batt insulation in the wall cavities, wall sheathing, a layer of building wrap (Typar), and the cladding (clapboards) – what you’ll see in most construction.
Highland (right): spray-applied mineral wool (not yet installed in the wall cavities), wall sheathing, 2″ of rigid foam on a nailing board with the seams taped, Blueskin fully-adhered membrane, a drainage mat, and then cladding (not yet applied).
Putting a layer of foam insulation on the exterior of the sheathing prevents thermal bridging (heat leaking through the wall studs), helps make an airtight seal, and keeps the interior wall warmer and less susceptible to condensation. The mineral wool in the wall cavities is fireproof, insect-proof, mold-proof, and helps provide sound dampening as well as being a great insulator. The details will vary a bit around the house – we’ll use rigid mineral wool at the sill to allow drying, use an ice and water shield and more rigid insulation on the roof, and the basement and sill interior will be closed-cell spray foam – but the overall goal is a well-insulated and airtight home with no thermal “leaks”, superior interior comfort, and lower energy bills.