I have an 1845 farm house with a stone basement about 2.5 ft thick. I had an energy assessment done and am losing a lot of heat thru the basement. We are thinking of using spray foam insulation on the walls.  I am  torn as I dont really want to cover up the stone with the srpay foam but I live in Ontario and  we are eligible for a government grant to cover most of the cost.  There will be some interior walls left in orginal condition.  Any ideas?? Pros vs cons?  Thanks   Cindy

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I don't know and time will tell like in the case of Aluminum siding. We thought it was great when it first came out but then years later we found out it was rotting our houses from the inside out. The materials used in the times gone by don't always mix with the new technology. By keeping the heat your house the mortar may be softened by moisture and condensation between the two temperatures. I still thing all the problems people are having with mold these days is because we are making out houses too air tight with all the tyvek house wraps, sealers, and insulation's. Houses are meant to breath a little. My parents used to insulate the basement using bales of straw on the outside. Not always the best look it did keep the house warmer. I would check into what damage sealing the stone foundation may do to the old mortar. Just my thought. Lair
Do you use the basement? I barely use mine, because of the low ceilings and many other shortcomings. If that is the same for you, couldn't you insulate the basement ceiling so that the basement is not connected to your heating area? Ontario is probably ridiculously cold, though, and maybe that changes the equation.
A traditional stone foundation is designed to release its moisture to the interior air space of the basement. If you apply insulation to the interior of the wall moisture will be trapped in the wall, which may very well lead to deterioration of the wall.

The stone foundation wall conducts some heat through the wall to the soil on the outside of the wall. This slight amount of heat keeps the frost in the ground away from the foundation, and prevents the frost from "heaving" against the foundation pushing the foundation stones inward. Heaving takes place because the water in the soil expands as it freezes. If you insulate the interior side of the foundation wall, the ground will freeze harder closer to the foundation and be more likely to heave stones out out place.

I have seen the combination of trapping moisture in the wall and that moisture freezing lead directly to stones getting pushed right out of a foundation wall within five to ten years, and in one extreme case within 3 years. I imagine that the frost in the ground in Ontario is much deeper and harder than here in Maine, USA.

If you are planning to save fuel dollars by insulating the interior of foundation wall, be sure to include to cost of future stone masonry repairs in your payback calculations.

There are many, many more effective ways to save fuel dollars. Since you really don't want to do it, why let the availability of a government grant influence your decision? "Free" now, does not necessarily mean free later.

John Leeke
Also, be careful about insulating between the first floor joists. Insulation can trap moisture in the joists leading to fungal decay. An important purpose of the basement is to provide a large volume of air that can absorb moisture from the wood keeping it dry and decay free.

I think spray foam insulation has a place (I used it in my home's walls), but it would not be my choice to spray it on teh surface of a stone or masonry wall. There is usually a lot of water and vapor drive coming off those..in many cases visible glistening from bulk water during rains..... and I believe you will indeed trap the moisture there. This will drive it upwards and to your sill plates, and possibly cause a mold problem.
I am new to the forum and have read your previous posts related to spray foam insulation (SPF-spray polyurethane foam) all the way back to January 2009 when you were deciding on what route to take and the methodology you subsequently employed around August 09. As I am considering a similar situation I would welcome your input.

I own an 1847, 5300 S.F. 2 story, w/ clapboard siding that needs to be replaced. The house was largely redone (if not restored) by the previous owners between 1994-98 and I have owned it since 2002. All of the major work (electrical, plumbing, hvac, etc.) has been completed and we have been fine tuning and upgrading as things need attention. The interior is finished and 90% of the original lathed plaster is intact. We are located in southwest Georgia, so we are in a predominately "cooling season" climate with the summers (mid May to mid Sept.) being hot and humid with highs in the 90's and lows in the 60's and the winters (mid Nov. to mid March) being fairly mild with highs in the 50's and 60's and lows in the 30's and 40's.

Since the siding will be removed, now would be the time to insulate and there is no doubt in my mind that closed cell SPF is the most energy efficient material available. I used it two years ago in the roof deck of a smaller and less historic house on the same property and what a difference in the HVAC load! As I would be spraying it in the wall cavities from the outside, my thought was to fill about 3" of the 3.5-4.0" cavity, then use Tyvek as required by code, then apply the new siding. There is no sheathing and I do not plan on installing any to keep from having to build up all the window and door trim. The attic currently has loose fill fiberglass on the attic floor providing for about an R-21 value and there is no insulation under the floor.

The SPF contractor indicates that he has done other old houses with lathed plaster from the outside with no apparent negative effects, but I am getting contact information to speak with these owners myself. He did mention that depending on if he encounters any gaps between the framing studs and the lath and plaster that he may need to "pre-foam" those areas with a low expansion foam before applying the closed cell to prevent the high expanding closed cell from getting in between and moving/cracking the plaster.

I welcome all thoughts and input.
Each case is different and depends in part of teh climate you are in, and there is always uncertainty associated with this. I can't tell you what you should do. But I can say that 3.5-4.0" of closed cell foam is a virtual vapor barrier and if you live in a warm climate,. it will tend to have a warm surface on the outside (facing out) and a cool surface on this inside (facing in to the house). You will not get condensation on the surface of the foam at the thickness you are using.

The fact that it would be away from the siding seems like a plus in my view, in that you allow for an air pocket to exist behind the siding. If you have 2 X 6 framing you likely will have a 2-2.5" air pocket between the siding and the foam, which permits drying out on the inside.

Sean is correct in that if you use foam directly on the back of your plaster and lathe, you would never be able to remove the foam without removing the plaster or vice versa. Also, I would be very cautious here -- I woudl take photos of all the interior walls BEFORE anyone sprayed so if there is buckling due to over explansion by a poor application, you will have the evidence.

If you are going to go this route, I think leaving that air space between teh insulation and teh siding is the way to go. Even though we did choose this spray foam route, I did agonize over the details and made the best decision I could make at the time. I believe in the end it may have been the right decision, but there are no guarantees.
Don't do it!... for all the various reasons already posted here. Is it really worth it?

It seems that people sometimes feel guilt over not being "green" enough. Replacing warm bulbs with expensive mercury laden CFL's to save a few pennies every month in electricity, is a good example. Wanting to cut your budget is one thing... thinking you can actually impact the Earth is another.

Here in the US Midwest many of the old farmhouses surround their foundations with bales of straw during the winter as already mentioned previously. It's not so airtight that you're going to get a lot of moisture build-up... rain will just drain through. But it's thick enough to block the wind and retain the heat.

I found that my sill plate was not sealed over the block foundation allowing a tremendous amount of air, not to mention bugs, into the basement. The air was passing around the sill where it covered the hole in each concrete block. It took a few dozen cans of foam but the entire sill is now sealed and the drafts in the basement reduced to zero. It stays cleaner and for the first time in decades, there are no crickets, no ladybugs, and very few spiders.

Paying a few extra dollars every month in energy consumption is a small price to pay for historical retention. Just use the energy guilt-free by enjoying life in your old house.
You said there is no sheathing? So you would be spraying the foam against the back of the original lath and plaster? I wouldn't do that. If you do have a problem later, then you will have to most likely remove all your original plaster.
Would using spray foam on the attic floor be ok? I was thinkg of doing it here soon, since it is getting cold in Mid-Southern Ohio now. I just have about an inch of rockwool now, in about 1/6 of the attic floor. I just don't want to cause any kind of other problems by doing so. I was thinking about doing spray foam in the basement under the 1st floor.. but that sounds like a bad idea after reading some of these posts.
OMG!!! I live in Michigan and bought a 140 yr old farmhouse this spring. The whole "Michigan basement" was filled with "Great Stuff" crap. My Mason couldn't believe it. It totally ruins everything. The previous owners put it everywhere in the house ie: corners etc. It ruined great hardwood floors because the crap expands. I hired a Mason to tuck point the whole basement. It was time consuming but the basement is draft free and looks 100% better.


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