Will some insulation need to be removed in a few years?
Our long-term plan is to add a deck/pergola/conservatory on top of a one-story room on our mostly two story house in Zone 5a. BUT, the roof on the single story leaks and will be unshingled/re-shingled NOW. We’ll use this opportunity to remove decking of the flat part of the roof (it angles from the flat part down to the three walls), access the inaccessible attic, and air seal/insulate before re-shingling.
I don’t know anything about building, so please read what I mean if I misuse terms. Some in on the project want to do a great job of air-sealing around the tops of the walls by spraying closed-cell foam in the angle of the ceiling and air baffles that will be mounted under the decking. I’ll guess this would go on the top plate and over the ends of the joists (cellulose will be used toward the interior), I think it’s likely the best way of air sealing/insulating this hard to reach area, and for a normal attic might be the way to go. BUT, seeing the rafters will come off in a few years and a new live-load floor added as a second story, I’m guessing new joists might have to sit flush on the top plate, their ends will have to be flush against the rafters or rim joist, some might have to be sistered flush to existing joists, a subfloor would have to be level on top of the combo of the old and new joists, etc.
Do surfaces that new joists/subfloors would rest on/against need to be so flat/level that a really good job of removing insulation must be done where new lumber will be added? If so, is closed-cell foam easily enough removed to accomplish this without much added cost? What about open-celled? If open-celled is easily removed, I still can’t use it because there’s no way of applying the vapor retardent paint to the surface that would abut the baffles under the angled roof, right? If neither should be used for whatever reason, is it reasonable to say that though carefully stuffing batts or cut board in the angle won’t seal/insulate as well as foam, it’s a good solution if some surfaces must be made level in the future? Thank you for your time.
Gordy_B
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Replies
Gordon,
I advise you to do a good job of insulating and air sealing now, when the new roof is going on. It's possible that your plan for a second-story conservatory may be delayed or abandoned, so it would be a shame to do a shoddy job of air sealing when you have the chance.
I'm sure that the carpenters will grumble when the time comes to remove some of the spray foam. But just because they will grumble, doesn't mean that installing the foam was a bad idea. Trust me -- they'll be able to remove the foam.
Thanks Martin! Anyone else? Addition going on in about five years on top of what's being insulated now. Stick with bead and/or tape sealing with removable rigid foam, batts, and cellulose because open or closed cell will be too hard to remove from the surfaces new joists etc. will sit on OR go for closed or open cell for the better sealing and insulating qualities, knowing it won't be a big deal to remove some of it in a few years?