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Insulating Concrete Block Walls

I live in central Florida and I have a concrete block home built in 1983. I am debating whether or not to have the spray in foam insulation placed in the walls. I have heard that this can save up to 25% on your energy bill.

I’ve been doing some research on the subject and it seems to me that the spray in foam insulation would not be that effective if it only filled the void within the concrete blocks. I have read that if the insulation only fills the void within the concrete block, it will only increase the R value of the wall by 2 (because heat can still be transferred through the edges of the concrete block, where there is no insulation). I was wondering if anyone had specific data on the subject – what is the R value of a concrete block wall with no insulation and how much does adding insulation to fill the void increase the R value of the wall?

From what I have said previously, it doesn’t seem like the R value of the wall increases significantly. I was wondering if there is any significant energy savings obtained by sealing any air leaks that may exist in the walls?

Getting the insulation installed will cost around $1000 and I want to make sure that it will be worth the money.

Re: Insulating Concrete Block Walls

I live in northern California and also purchased a concrete block house built in 1951. Out here summers are warm (80 to 100 degrees F) and winters are cold - sometimes down to freezing with occasional snow. We are in a wooded area with a lot of shade, so summer temps are not too bad but winter temps keep the walls very cold. The previous owners only used the house in summer and wintered in Arizona.
In order to insulate, I framed the interior of the house as you would any newly built house, put R-15 insulation between the studs and drywalled it all. That worked OK for most of the house but in areas like the kitchen and bathroom where you can't get to the walls without major renovation, the walls are still bare and cold. By doing this, I decreased the size of rooms by 4 inches for each exterior wall.
If you find a better way, I would appreciate knowing. Also how to insulate the walls from the outside, if possible.

Re: Insulating Concrete Block Walls


The webbing of the cement block is a significant thermal bridge through which heat gains access to your home. Have you considered clading your home with insulating foam and either new siding or synthetic stucco? Insulating cladding on the outside of the walls would keep the Florida sun from heating up your walls in the first place. My brother-in-laws' 1976 house in Germany has just such construction. DryVit, which is a German company, is one of the leaders in the synthetic stucco field.

Synthetic stucco has to be properly installed on wooden homes to prevent rot, but many of those problems are not a concern over cement block or concrete.

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