Home Fix: Insulating an older home

Q: Just bought a 1910 house in Queen Anne. We love the house, but it’s very chilly.

I thought I would start with insulating the basement because I can feel jets of cool air coming in a certain points when walking around down there. I also need to install a dryer vent, so I removed a section of the lath and plaster, removing the interior lath and plaster to expose the stud bays. There was no sheathing, just what appears to be tar paper behind the clap boards.

So now my question is, how to insulate? Everywhere I look recommends something different. I am concerned about a vapor retarder and trapping water in the wall that will lead to mold. I thought about doing rigid foam insulation surrounded by spray foam. But I hear that will leak over time when the house contracts and expands. Considered batts, but how does that seal air leaks? Any advice would be appreciated.

A: The tarpaper on older homes is an excellent air and moisture barrier, much like the house wraps used today. Insulating older homes presents several problems for the average homeowner. For instance, using a rigid foam insulation provides resistance to thermal transfer, but the foam board cannot be left uncovered.

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