Sunday, February 23, 2014

Insulation Phase 1

The (official) insulation contractors arrived today along with all the materials. I say "official" because you will recall, the design for the New House Next Door called for a hybrid approach and the exterior continuous rigid insulation has already been installed. See previous posts from November: Foundation Insulation and December: Rigid Exterior Wall Insulation

First of all, let's talk about energy use and sustainability. One of the best ways to be "green" is to have a super tight "building envelope" (the line between inside and outside) and therefore minimize the resources needed to heat and cool your house. Insulation -or R-value- is not the whole story; air sealing is actually even more important.

Spray Foam @ Crawlspace Box Beam

The energy code allows designers a few different methods for achieving the minimum requirements. Because this is a small house, (Sizing a house appropriately/modestly is the single-most important way to build green) I could use the prescriptive method. I followed Energy Star Standards, meaning the walls have that continuous rigid insulation (CI) everywhere, in addition to the cavity insulation between studs. And because we have the high efficiency CI on the walls, I used plain, old (inexpensive) fiberglass batts in the wall cavities. Then where it really counts, I specified spray foam (a more expensive insulating material, because it is also an excellent air-sealer) for the roof and at each of the floor lines (called the "box beam"). And the roof trusses we designed/installed to allow for full depth insulation over top of the walls- read more about this at the post about the trusses:

Spray Foam @ Underside of Roof

The last item to mention is the location of the building envelope. Many existing houses have insulation in the ceiling of the top floor and between the floor joists of the bottom floor. This was common practice, at least here in the NE... But building science has taught us that rather than having an un-insulated, un-conditioned attic and basement, it is more efficient to condition those spaces and have the exterior surfaces (roof plane, foundation wall) create the building envelope. Different... If you want to learn more, check out: They have an amazing amount of information.


  1. Gosh I'mm learning a lot! Almost want to build a new house just to get all this cool stuff.

  2. I know how you feel! All these "high tech" building materials are exciting and changing all the time, of course. Think of how different the construction of this house in 2014 is different than when P & D 's current 1820s farmhouse was constructed! It wouldn't have even had indoor plumbing and all the construction would have been accomplished with hand tools!