| 1168.1 |
| I would like to insulate the exterior walls of my cottage on Georgian Bay. The buildings are about 60 years old, and were not intended for winter occupation. There is no sheathing material in the construction. Lapped 1×6 western red cedar boards were nailed directly onto the studs. When the interior panels were removed to upgrade the wiring, I could see that water had penetrated the spaces between adjacent boards. If I were to fill the entire stud cavities with some type of insulation material, I suspect the moisture that penetrates would remain inside the wall cavity and create problems with time. I had an idea that goes something like this. If I nailed 1/2 inch spacers vertically to the inside surfaces of the siding, I could cut rigid foam insulation panels to fit the stud bays and install them against these spacers. The remainder of the cavities could be filled with blown insulation, since standard bats would no longer fit. This would provide a one-half inch air space behind the exterior walls, and maybe enough air would circulate in these spaces to allow the walls to dry out after a heavy rain. Any comments would be greatly appreciated. I am a do-it-yourselfer without a lot of knowledge of such things. Cam |
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Replies
I renovated a similar old house for my in-laws in a high wind area on a bluff in Southern MD. We just stapled a6" wide strips of 6-mil plastic to the studs, pushing it against the backside of the siding, then normal batt insulation. Eighteen years later, water build-up hasn't seemed to be a problem.
That house is balloon framed, though, so some infiltrated water would go all the way to the lower sill, 10" below the first floor, and leak out down there in the crawl.
Forrest
Here is a SWAG: My first thought is sprayed in closed cell foam as it is mostly impervious to the absorption of water. Lots of $$$ though, and you would still need to make sure the wall assembly would dry properly.
Cam -
By insulating the wall cavities you will lower any potential for drying if the cavities get wet. Your walls have managed to survive water infiltration in part because there is no insulation so the cavities can dry more easily (you are effectively heating that space n addition to the rest of the cottage now). By adding insulation, the sheathing will be colder (in winter) than it is now and you will reduce the potential to dry.
You would do well to add a real weather barrier under the sheathing before you insulate. You could possibly also insulate in this step by removing the sheathing, adding rigid foam to the exterior of the studs, then reattaching the sheathing over furring strips. You may need to add a housewrap somewhere since foam isn't intended to be a weather barrier for high rain areas. You may also need to add some plywood to combat racking. Detailing at windows and doors may be difficult, however, as a retrofit.
You mention that you have interior paneling which is probably not an airbarrier - another reason for the approach above. Currently you do not have an interior or and exterior air barrier and adding one would accomplish more than insulating alone. The above accomplishes and exterior air barrier and insulation in one step.
You should check out the buildingscience.com website.
I think it would work.
What condition is the bottom sill? Not rotted?
If you cut the foam a little small, you can get a foam gun & foam it all in place to seal the foam to the studs.
This looks like a knock off of a Prageis gun, Ebay for $28.
http://cgi.ebay.com/Foam-Insulation-Professional-Applicator-Gun-New-in-Box_W0QQitemZ6054848988QQihZ009QQcategoryZ41991QQssPageNameZWD1VQQrdZ1QQcmdZViewItem
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A couple cans of foam should do your Cottage, don't get it in your hair.
Joe H