The House: Insulation

At the time we bought the house, it had standard walls for this area — 2×4 studs and R12ish insulation. The original house had been built as a cottage, though, and so the insulation had been added later. In removing the wall panels, it was discovered that some areas of the wall had been deemed too tough to reach or simply forgotten during renovations and so were not insulated. Although there was vapour barrier in places, it was patchy and entire sections of wall were omitted. It was no wonder that in our first winters the baseboard electric heaters were sometimes going full tilt just to keep the temperature above 50F(10C).

Fortunately at the time, Canada has a program to help with the cost of upgrading houses with respect to energy efficiency. An energy auditor would come to your house and make notes regarding the construction of the house, the nature of appliances and windows and do an air infiltration test. Renovations could then be completed and a second audit done. Based on the changes made, you could then apply for reimbursements to certain dollar amounts based on a schedule. Better still, the dollar amounts were based on substantially compensating someone who was hiring out the work. By doing the jobs yourself, it opened up quite a reasonable budget for materials.

Staggered stud walls with bulkheads

The construction of the outer envelope. Bulkheads on the load bearing walls allow for the addition of more insulation than the attic space alone allows.

Unfortunately, money was only half the battle. There were several inconvenient aspects to our house. The attic was too low at the edges to house substantial insulation without resorting to spray foams. The crawl space under the new section of the house was only inches tall and did not grant one access. On the bright side, we wanted to change the house layout and the arrangement of windows on the exterior walls and so we were committed to a fairly intrusive process anyhow. I will detail changes to the layout in the next entry, but suffice it to say for now that the first step was stripping back the house from the inside to just its basic framework. This was done in sections, allowing us to set up “Dexter Kill Chambers” (areas tented with plastic) in which to live as we proceeded. Changes to the exterior wall to accommodate windows or to repair structure where it had been compromised by previous renovations were completed at this time. A second wall with studs offset from the outside wall was then erected inside of the exterior wall, with the space of a couple inches between. This wall was shorter along the load-bearing walls to accommodate the construction of a bulkhead, which in turn allowed for the installation of vapour barrier and insulation below ceiling level to compensate for there being inadequate space to install lots of insulation in the attic.

Staggered stud wall

Staggered stud construction reduces thermal bridging. Batts are R20 and R14, with small parts of insulation cut to fill the remaining voids.

Insulation was then put in the walls — a mix of R20 and R14, carefully cut and fitted so as to fill the entire void. Vapour barrier was installed on the inside surface, including travelling around the ceiling joists to meet up with the vapour barrier in the ceiling. This being done, our outside walls looked like this:

In addition to having a greater nominal insulative value of R34, the staggered studs removed the thermal bridges the studs create in conventional construction. There is now no way for heat to conduct through the walls without encountering at least some fibreglass along its route.

The vapour barrier going around the ceiling joists took a lot of tuct tape but allowed for vapour barrier to be layed on top of the ceiling joists, covering the existing R12 insulation in the ceiling. Batts of R-40 attic insulation were then layed into the bulkheads and over top of the vapour barrier in the attic. This was supplemented where it would fit by new R20/R14 left over from the walls or purchased new as well as old insulation pulled from the walls provided it was in good condition. The end result is a massive stack of insulation in the attic, while still allowing adequate ventilation. In order to ensure proper air flow, rigid foam attic baffles were installed at the edges, ensuring that air could flow from the soffits up into the main cavity and out the vented peak.

The last part of the equation was to install insulation in the floor. Although I had provided supplemental drainage for the foundation and put vapour barrier over the bare earth, crawl spaces are still inherently damp places. We did look briefly into spray foam but at the time couldn’t find anything at a reasonable cost and even had refusals to work in the crawlspace given its cramped dimensions. Instead, we resorted to Roxul, which is far more resistant to dampness than is fibreglass batting. The next problem we had was that the floor joists in the original section of the house were only 2×6. This not only resulted in minimal place for insulation but also left the floor pretty flexible, even after bracing the center beam. The first step here, therefore, was to screw-and-glue 2x4s along the edges of all the joists. This helped increase the stiffness of the joists as well as providing added depth for insulation. Roxul was then installed — 2 R14 batts for a total of R28. Mesh was then installed below this to keep out animals and keep insulation in.

A mix of old and new framing during the transition in layout.

The newer section of the house had much more substantial floor joists but had the problem of being inaccessible from below. Thus, we were required to tear up the subfloor in that section of the house and install a similar system from above. This was an interesting process, as the residual heat and dampness under the house had made it an excellent breeding/overwintering spot for mosquitos. Upon tearing up the subfloor we released thousands and thousands of mosquitoes into the house in November. Fortunately, the process of putting vapour barrier over the dirt, mesh under the joists, insulation between the joists, vapour barrier over the joists and a new, more sturdy subfloor ensured that the escaped heat and residual moisture were no longer sufficient to support our mosquito population and we no longer have that issue.

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