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Concrete block house from 1904

Chovanec | Posted in General Questions on

I have a home in northwest Ohio. The home was built in 1904. The construction is concrete block.
I have converted the home into two rental units. I have two boilers
the lower unit has a 100,00 btu boiler and the upper unit has an 80,000
byu unit. both boilers have a single loop. My problem is when the temperature
drop to 15 deg. I can only get the building up to 59 deg’s.
I have replaced all the windows with insulated glass.
I am thinking about installing a foam board type of insulation on the inside of the building
can you recommend a product?
I am concerned if I use a board foam insulation I will trap moisture between the wall and the back side of the foam board.
Can you give me some advice?

Regards SMC

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  1. Expert Member
    Dana Dorsett | | #1

    Insulating the block walls with foam on the exterior is the way to go. It would hit current code-min with as little as R13 continuous foam on the exterior. A purpose-made retrofit system from InSoFast would make it pretty easy, but it's panels are only R10, not quite current code:

    It would be MUCH cheaper instead to use 3" of reclaimed roofing EPS on the exterior, strapping it to the block with 1x4 furring through-screwed into the masonry with 5" masonry screws (use cap screws or fender washers to keep it from splitting the furring) works, hanging new siding on the furring. There are several companies in your area trading in reclaimed & factory-seconds foam, judging by this quick search:

    Don't worry about trapping moisture between the wall & foam. A spray-applied weather resistant barrier ( ) on the block will keep the interior dry, and if the foam is EPS instead of polyiso the foam can take it. If the block is so smooth you're still concerned it won't drain, a mesh underlayment such as the 1/4" version of John Obdyke Rain Slicker ( ) would allow ample drainage without totally undermining the performance of the foam. With a drain mesh underlayment it's fine to use polyiso. To hit code min with polyiso takes 2" of foil faced polyiso or 2.5" of fiber faced roofing polyiso.

    160KBTU is a lot of burner! It's a bit surprising that boilers that big won't keep the place up to temperature, unless it's a VERY large house. I suspect you may be radiation-limited, not burner limited. It wouldn't surprise me at all if the radiation can't even emit heat at even half the boiler's burn rate. Can you describe how much radiation & type there is on each zone?

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