Cuthbert Renovations – Day 16; “Insulationist Theories”
Tuesday, September 30th, 2008Previously, I detailed how the ceiling joists were replaced over the master bedroom and closet, thus allowing for proper insulation. Well, this is the other half of the story. The photos above show the ceiling above the Bathroom and Guest Bedroom. The ceiling in these rooms are not in our scope of work, nor was the attic, but the insulation situation was cause for concern.
Concern #1: The insulation is a rock wool bat installed between 2×4 joists. This type of insulation has an R-value of 3.5 (basically, R-value is a measure of resistance to heat transfer, or how well it holds heat in; the higher the number the better). At a thickness of say, 4 inches, the R-value is 3.5×4=14. This value assumes that the insulation is not compromised by gapping or product deterioration. In this case, I’d be willing to take the under. Modern building standards for attic insulation is R-30, so this is clearly below par. This whole area represents a weakness in the thermal boundary between the conditioned space below and the unconditioned space in the attic. As you can imagine, this thermal bypass causes heat loss in the heating season, and heat gain in the cooling season. Long story short, it’s a waste of energy and a waste of money accordingly.
Concern #2: Look closely at the picture above. See the pink insulation in the center of the triangle. It’s different than the rest of the insulation up here, so it must be pretty important, right. Or maybe it’s just hiding something. Keep that in mind, and we’ll come back to it shortly.
Proposed Solution: Several insulation options were explored for properly insulating the attic. Ultimately, it was agreed upon to remove the remaining insulation and replace with new fiberglass bats that will match the R-value of the new work over the master bedroom.
Follow Through: Decking was pulled up, old insulation removed, and the bays were vacuumed to remove any remaining dust and debris. Now, remember the pink insulation in question earlier? Under it we found a bath fan! Bath fans are important because they remove moist air out of your house…except when it’s not vented. In this case, no ducts were installed to the outside, so the moist air simply blew into the attic. Less than ideal. Easy fix though; we’ll just add a duct and vent it through a side dormer without disturbing the roof. ?

































