Living Efficiently With Tom: Crawl Space Insulation
Thinking about making energy efficient home improvements? Home insulation is a classic homeowner example that comes to mind. Despite long-held aspirations, it was only recently that I tackled the project of insulating the crawlspace beneath my dining room. Cold floors during winter months finally convinced me it was time for insulation.
Choosing the Target
First there was the challenge of getting the large foam board panels home — they certainly wouldn’t fit in our small car. Finally, with a van rented for an unrelated home improvement project, I was able to get three of the 4-by-8 feet sheets home. Procrastination left them waiting in my attic (although, in theory, they helped a little just by lying on the floor up there) until they were featured in a recent interview on changes in energy efficiency tax credits with a local television station. With the added encouragement that they be installed before New Years to claim a 2010 tax credit, I was moved to action.
Getting Started
My first task was to tidy the space up. Fiberglass offers less insulation when it’s bunched up as some of this was. I needed to get the foam board snug against the joists to securely nail it into place and to reduce any air flow above the insulation, which the various scraps of wood and siding would prevent. A temporary solution came in the form of large quantities of duct tape held to the joists with equally large quantities of heavy-duty staples. Once in place, the foam board held the old fiberglass up.
Choosing Insulation
The insulation I chose was the most insulating rigid foam board I could find locally. It has a radiant barrier lining on one side which allowed it to face towards the conditioned room and reflect heat in or out, depending on the season. The other side has a moisture barrier to face outwards and limit dampness getting into and through the insulation, which could cause mold.
The 2-inch thick polyisocyanurate closed-cell foam is rated “R-12.” R values measure the insulation’s ability to resist heat flow. The higher the R value, the more effective the insulation is. The R-12 foam is a great deal more insulating than fiberglass batts and also controls air flow that might cause drafts. Added to the existing fiberglass between the joists — about 4 inches worth — this project easily exceeds the insulation value needed to qualify for a tax credit. It’s not a big credit, though. This was a pretty cheap project. It cost about $100, making it worth a whopping $30 credit on my 2010 income taxes. But hey, every little bit helps.
Missteps Along the Way
After cutting the foam board sheets to size, and maneuvering them into place (requiring the much appreciated assistance of my wife, who had to be called into the dust of the crawlspace), I had a bit of a learning experience as the nails affixing the first sheet began to pull through the foam board under the force of gravity. This was not entirely unexpected — I had tried to find long roofing nails for this project, as they have a plastic disc about an inch wide to prevent them from tearing through roofing materials, but I was unable to find roofing nails long enough to go through the 2-inch insulation and into the joists. My gamble with regular large-headed nails did not pay off.
While scrambling in the dust to keep the nails from tearing through the foam board, I happened upon a ready solution. There were plenty of scraps of relatively thin wood laying about that had previously been used in attempts to hold the old fiberglass insulation in place. Fortunately, the nails I had were long enough to go through small scraps of this wood, through the foam board and securely into the joists. We were back in business.
Once all three sheets were in place, some spray foam into gaps and vapor barrier tape on seams between the sheets and over nail holes ensured that everything was nice and snug to prevent outside air bypassing the insulation.
Mission complete.
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