Overwintering a Gutted House
We’ve recently gutted our house in Zone 6 (Southwestern Ontario — cold and very snowy) and won’t be able to complete the renovation before winter. We have to decide whether to (1) try to overwinter without insulation (in ceiling or walls), or (2) modify the plan in an attempt to get the house at least partially insulated over winter. (It will be unoccupied.)
The house is a small single story with full basement, heated by a forced air propane furnace located in the basement. The basement is only accessible from a separate outdoor entrance (there are no indoor stairs). It’s currently the only part of the house still insulated and has historically been one of the warmest, driest areas of the home in winter. There is (appropriately) no insulation between the basement and main floor, and several areas have been stripped to the subflooring.
Option 1: Overwinter with no insulation
As I mentioned, we’ve gutted the whole main floor, including the cathedral ceilings and attic, but the basement is still insulated.
We can shut down the water and drain the pipes, but have been told that frost heave is a concern in our area and may cause permanent damage to the foundation. The furnace is in the basement and we could move the thermostat to the basement and continue to run the furnace with the goal of keeping just the basement above freezing.
Has anyone done anything like this? Are there risks I’m not seeing? Bear in mind that the upstairs will be vented through the roof soffits into the uninsulated, unheated space. Will this create frost and moisture problems? Or, given that everything is open, will any frosty or wet areas be able to dry adequately in the spring?
Option 2: Reinsulate before winter by compromising on the original plan
Alternatively, we could make some effort to reinsulate by:
Insulating the 2×6 walls with rockwool and sealing them with poly (required in Canada), but NOT drywalling at this point. The reason not to drywall at this stage is because we plan to move some doors and windows and replace others, but that won’t happen until next year. I know poly can provide some air sealing if done right, but without the extra benefit of drywall for further air sealing, do we risk letting too much moisture into the wall cavities? This concern might be lessened by the fact the house would be kept only moderately warm over the winter (around 10C to 50F) and would be unoccupied so have less human-created moisture. I’m also a bit concerned about the mess that might be created by the acoustical sealant on the poly in the areas that we end up moving/reframing next year. Can it be scraped off and reapplied in a a few areas if we need to get into those wall cavities?
Sprayfoaming the cathedral ceiling BEFORE removing shingles and inspecting sheathing from the outside. Our ultimate plan is to replace the roof shingles with standing seam metal roof and to spray foam the cathedral ceiling to R40-R60 to make it a hot roof (not the greenest but a compromise to save a house with a difficult roof — low slope and hard to properly vent due to offset peaks). Gutting revealed some signs of water damage / light mold on the interior of the roof sheathing (see pictures). This occurs only over the kitchen and bathroom and I think it’s possible it’s on the inside only and is from moist air leaking into the cathedral ceiling cavities (poorly air sealed and no vent fans). Is there any way to confirm this from the inside? If we do gamble that it’s interior damage only and get it spray foamed this year, then later find the sheathing fully compromised when we strip the shingles next year, how big is the issue we’re creating? Can we still have roofers replace the sheathing in a few areas and get those cavities re-sprayed for a bit of extra cost, or does this create significant problems?
Having set this all out I’m leaning towards Option 1, but it would give me some reassurance to hear from people who have done this in a cold area.
Thanks in advance — any thoughts are much appreciated!
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