Cold exterior wall

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Posted by: from Belleville
2/20/2012 at 10:00:10 AM

All my exterior walls are cold to the touch on my main floor. My main floor walls are plaster walls. Should I get blown in insulation or remove exterior wall and put new insulation in and put up drywall?

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Date/Time2/20/2012 at 12:13:49 PM

Hi David,

There is a product that I have used in the past referred to as Icynene Pour foam. It is injected into the wall cavities and expands 60 times its initial volume without removing the wall.

You do require at a minimum the existing plaster to be installed on strapping to leave a cavity in behind. The other alternative as you suggested is to remove the existing plaster, re-stud and I would suggest using spray foam to achieve better R values and air leakage while minimizing the stud size.

Hope this helps.


Kingsway Construction Inc

Glenn Rosborough

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Date/Time2/20/2012 at 5:20:52 PM

Foam is the best product, however it is not cheap. Another alternative would be blown in insulation, assuming you have a cavity behind the plaster. It involves 2-3 holes to be drilled in each stud cavity, similar to the foam, only larger. If there is no cavity, then you will have to build interior walls.

Another alternative would be to insulate from the outside. It would involve siding the whole house, but would be cheaper than the interior route and not take away from your floor space.

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Hamish from Natural Solutions in Coquitlam
Date/Time2/20/2012 at 7:42:15 PM

Hi David, well, if I was you I would be pricing out the blow in insulation .

To get the old lath and plaster off if a lot of dust and cost, so to speak ! Besides, the old plaster is a lot more hard warring than dyrwall.

The blow in would be much easier fix, and your walls will be insulated.You should be conforming to code (At least in the Lower Mainland) with an R14 insulation, so check on the R value that the blow in will give you.


Hamish W.

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Date/Time2/21/2012 at 12:14:15 PM

Hi David,

To use bow in insulation will be much cheaper, and much less mess than removing the old plaster. There are a few things you do need to know before you can make an accurate decision. One of them is how deep your wall cavity is. If you don't have a large enough wall cavity you won't be able to use foam or loose insulation, and in this case you would have to remove the plaster to get the Insulation value you would like. If you do have a large enough cavity then you will find that foam is much more expensive than loose insulation. So this may factor into your decision as well. Foam does have the greatest R-value though.


Matt O'Coin

Marquise Construction

Belleville Ontario

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Date/Time2/22/2012 at 9:01:29 AM

Hi David,

Your problem is a common one in all older houses. It is important to determine the type of construction used in your house.

If it is what is known as a "double brick" house, you will find that the space you have behind your plaster walls is only 3/4" wide. Filling this area with any type of insulation is completely ineffective. However if your wall is constructed with some form of wood framing, then a loose fill product like blown in fibreglass, cellulose or sprayed in product like open cell icynene or polyurethane or closed cell polyurethane would be beneficial. The thickness of the insulation really is an important consideration in calculating the value of the application.

There is something else to consider that is equally important and that is air and vapour movement. Right now it is likely that your home is leaking air at a startling rate. This is terrible for energy efficiency but great for drying surfaces out. Once you fill the cavity in your walls you can actually create a far greater problem and that is moisture retention which leads to the development of mold and mildew. Of the types of insulation used for cavity fills listed above, only closed cell polyurethane acts as a vapour and air barrier. It is also the most expensive option and as with any sprayed in application that expands greatly upon contact with air, it is quite probable that you will bow out your interior plaster walls, possibly even breach them.

All of the cavity fill solutions (unless it is a framed wall) are simple band aids with all of the focus on not having to spend money on "non-insulation" work. It seems to make sense but really is the opposite. You will be spending a great deal of money to gain about R-1 (if it installed correctly everywhere) and have to patch holes all over your walls and possibly trap moisture and create a serious mold problem.

The best solution is to either create a larger cavity and insulate and vapour barrier correctly (interior framing) or add a "blanket" to the exterior either by closed cell rigid foam covered by some type of siding (complete new look for the house as well) or open cell rigid foam (lower R value) and an EIFS (stucco) coating. The latter of which will add about R-4.5 to your wall. These are more invasive measures but are the only ways to achieve any real gains. For the RValues of common insulation have a look at CMHC's website

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