R-value...Priceless
We asked Laura Campbell, AIA, LEED AP Home, from Peabody Architects, to write a guest post on the different kinds of insulation used in our home. Here are her words…
If you want a house that is comfortable, and inexpensive to heat and cool, then you need good thermal resistance and air sealing. In layman’s terms, that’s insulation and caulk. Not very sexy, but dollar for dollar, those are the most effective things you can do to make your home more energy efficient.
In this house, where budget played as much of a role as energy efficiency, we used three different kinds of insulation: expanding spray foams, fiberglass batts, and rigid boards.
The gold plated version of this house would have used spray foam everywhere. Open celled spray foams (like Icynene or Demilec) are sprayed in as liquid, and then expand into foam. They serve to insulate AND air seal, which is why we like them. They are also the most expensive kind of insulation. In this house, where we were keeping an eye on energy efficiency and budget, we used them only in the roof, at the connections between floors, and at hard-to-reach places.
Why is the roof so important? In the winter all the heated air in a house wants to rise and leak out through the top of your house. No matter how carefully you caulk, it is hard to stop this pressure drive. The spray foam really pays for itself at a roof. We also used it at the rim boards between floors, at windows, and at electrical outlets.
We used standard fiberglass batts at the walls, with caulk to Energy Star standards. Fiberglass batts provide good thermal resistance provided they are installed correctly (fully filling each cavity). The caulk provides the air sealing.
At the basement, we used rigid board insulation at the walls. While costing a bit more than fiberglass batts, it provides good moisture resistance, and adds a few inches of extra space. We also used it under the concrete slab, which will make this basement toasty and warm in the winter!
