How to insulate my uninsulated house?
I live in a house in Kamloops, BC (40c in summer, -20c in winter, dry climate) that was built in the early 1950’s. From inside out: Drywall, Foil-backed paper, 2×4 framing, Drywall (local plywood shortage at the time of construction), Tarpaper, Wood siding. There is no insulation in the stud cavities. The exterior is due for replacement, and I would like to add some R value at the time. I have researched PERSIST designs, and think it would work, but have a couple of concerns.
1) We do not have central air. Would this lead to a lack of air exchange in an air tight design? Could it be offset with exhaust fans?
2) Would the drywall exterior sheathing be OK to cover with peel and stick membrane. Don’t see why not, but have not seen it addressed. Furthermore, would there be a problem adding the insulation directly over the existing siding?
3) Would the system work if the roof was left as is with a blown in attic?
4) Would there be a failure if the Insulation added to the outside was only 2 1/2″ thick (R 12.5)?
Thanks in advance.
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Replies
Ben,
Q. "We do not have central air. Would this lead to a lack of air exchange in an air tight design? Could it be offset with exhaust fans?"
A. Every tight house should have a mechanical ventilation system. There are lots of ways to ventilate a house: with an exhaust system, a supply system, or a balanced system. More information here: Designing a Good Ventilation System.
Q. "Would the drywall exterior sheathing be OK to cover with peel and stick membrane?"
A. Yes. However, many PERSIST builders skip the peel-and-stick and put the rigid foam directly over the sheathing.
Q. "Would there be a problem adding the insulation directly over the existing siding?"
A. It depends on how bumpy it is. Whatever you do, you need to plan a way to ensure an airtight installation, and you need to think through your window flashing details.
Q. "Would the system work if the roof was left as is with a blown in attic?"
A. Yes. The combination of PERSIST walls and insulation on the attic floor is called REMOTE. More information here: REMOTE: A Manual.
Q. "Would there be a failure if the Insulation added to the outside was only 2 1/2" thick (R 12.5)?"
A. No. But of course, the more insulation, the better.