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I'm helping out a group which is restoring a early 1900s farmhouse. One of the things they want to do is better insulate the house. One contractor has proposed spraying foam insulation on the underside of the roof in the attic. I have concerns about doing so and wonder if anyone can suggest some of the possible downsides to doing so--as well as comment on the cost effectiveness. I think there are much more important areas to insulate and I'm concerned about creating a moisture barrier under the roof. Plus, how long might it be before it starts to deteriorate?
Also, they are considering drilling into the mortar of the outside bricks to spray foam insulation into the wall space. Since the wiring is older (redone in late 40s/early 50s) I can't help but think that would make it much more difficult to re-wire the house when it comes time to do so. The interior walls are typical wood lathe and plaster.
Any thoughts about either of these proposals? Any other downsides or possible benefits? Thanks!
I'm helping out a group which is restoring a early 1900s farmhouse. One of the things they want to do is better insulate the house. One contractor has proposed spraying foam insulation on the underside of the roof in the attic. I have concerns about doing so and wonder if anyone can suggest some of the possible downsides to doing so--as well as comment on the cost effectiveness. I think there are much more important areas to insulate and I'm concerned about creating a moisture barrier under the roof. Plus, how long might it be before it starts to deteriorate?
I don't know much about using spray foam insulation up against the underside of the roof sheathing. I've thought about doing this with my own attic, but I haven't done much research into it, yet. I know there is some debate about it; mostly about whether or not you should allow some kind of space for venting between the insulation and sheathing. But I will say that the attic/roof is one of the first areas you should insulate.
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Also, they are considering drilling into the mortar of the outside bricks to spray foam insulation into the wall space. Since the wiring is older (redone in late 40s/early 50s) I can't help but think that would make it much more difficult to re-wire the house when it comes time to do so. The interior walls are typical wood lathe and plaster.
Any thoughts about either of these proposals? Any other downsides or possible benefits? Thanks!
I wouldn't drill into the mortar joints to inject foam insulation, but I wouldn't remove the interior plaster, either, unless it's in poor condition. Good electricians, that have experience with old houses, can do minimal damage to the plaster, so that it can be patched. In my own 112 year old house, since my plaster walls are in decent shape, I plan to just leave the exterior walls uninsulated.
Debate-
Roofing manufacturers want their product vented- obviously can't do that with foam under the decking
Roof damage, won't know there is decking damage for a loooong time.
I still believe the best overall "system" is a combination of radiant barrier, vented attic, and at least R-38 blown-in fiberglass insulation.
As for the walls- if there is any doubt about the electrical in the walls- upgrade now. Then you can proceed with foam injection. As previously noted, good electricians can fish wire with little to no damage requiring repair.
A thick layer of fiberglass insulation will he put in the attic. That's a given. Thanks for the comments to date. Any others? I'll rep all once this goes a bit longer.
Personally I would recommend against "sealing up" a roof / attic system that had survived for 100 years. Inviting trouble!
Similarly the risks of creating a real nihgtmate scenario for water intrusion / vermin infestation by drilling into bricks far offsets any potential for energy savings from "injecting" insulation which more that likely will NOT make it into the cavity in any uniform way...
If moisture gets trapped behind the injected foam you'll a literal zoo of fungal growth in there --
Debate-
Roofing manufacturers want their product vented- obviously can't do that with foam under the decking
Roof damage, won't know there is decking damage for a loooong time.
I still believe the best overall "system" is a combination of radiant barrier, vented attic, and at least R-38 blown-in fiberglass insulation.
As for the walls- if there is any doubt about the electrical in the walls- upgrade now. Then you can proceed with foam injection. As previously noted, good electricians can fish wire with little to no damage requiring repair.
^^^ All this. Especially the recommendation for radiant barrier rather than sprayed foam insulation.
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Especially the recommendation for radiant barrier rather than sprayed foam insulation.
