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jhedger69 07-22-2010 01:57 PM

Insulating above grade concrete wall
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Hello all. I am new to this forum and am in the middle of gut job remodel. My house is a brick cape cod. It has a brick facade and poured concrete walls. I do not believe there is any type of gap between the two. My question is, how do I insulate my exterior walls? I just tore down the plaster walls which were attached to the poured walls by furring strips. So now I'm looking at bare concrete walls (well, nearly bare - see the pics. They are poured concrete with a running thread of brick in-between. It's really odd! Also note the picture still has the furring strips on the walls but they are now removed). There seems to be some disagreement among the contractors about whether or not a vapor barrier needs to be in place before bat insulation is placed because it is above grade. I do not know if the walls 'sweat' at all. One contractor has said there's no needs to put a vapor barrier for above grade wall. Another says I need to a paint sealant (Drylock?) on the walls before I do anything. What my plans are is to construct timber framing up against the concrete wall and then fit the insulation between the studs. I cannot afford the foam spray insulation, because it is not DIY friendly and very expensive. But I have also been told it is the best for my situation. My house was built in 1950 and I'm in southern Ohio, btw. Any thoughts or suggestions would be appreciated.

jklingel 07-22-2010 02:47 PM

You could glue XPS to the wall, then secure w/ firring strips, also attaching sheet rock to them. Securing to concrete will be fun, but doable. The best place for the XPS is outside, if possible. j

concretemasonry 07-22-2010 04:35 PM

You do not have poured concrete walls above the basement and there may be a 3/8 to 3/4" gap between the block and the brick.

Do NOT use batts (especially fiberglass) applied to the wall. As suggested earlier, use XPS (not the white EPS beadboard) applied directly to the concrete masonry units.

With a massive XPS wall insulation on the exterior with a veneer (stucco, brick, etc.) id ideal, but you change the appearance considerably. Exterior insulation allows you to take advantage of the thermal mass of the wall for comfort and economy.


forresth 07-22-2010 05:17 PM

the rows of brick are to tie the brick and the block together. I'm guessing there is no gap, but you could compare the length of the bicks to the width of the wall to get a better idea. If there is or is not a gap, it doesn't matter. air gaps act as insulation too.

if you put siding over your brick, your house will lose value and require more maintenance. Why would you do that if the bricks are still good?

Thermal mass is thermal mass and will have an effect no matter what side the insulation is on

how much added width can you take before it becomes a problem?

one nice thing about the glued up sheet insulation is it can be put up without a wooden stud breaks to act as a thermal conduit. I'd then do 1" or 2" stips (probably secured with masonry screw thought the foam), then the drywall. like I said earlier, the airgap will act as insulation too. I believe you could glue the drywall directly to the insulation too, but I don't think I'd trust that so much over the long run.

stuart45 07-22-2010 06:03 PM

You could use an insulated plasterboard put up with the dot and dab method.

jhedger69 07-23-2010 07:01 AM

Thanks everyone for your suggestions! I am not covering the exterior brick. The insulation installation is strictly being done on the INSIDE of the wall, not exterior.

concretemasonry 07-23-2010 08:06 AM

The brick course is probably a "header" course, although different terms are used for the description. This course of brick is laid across the wall every two courses of block vertically to tie the exterior brick to bearing part of the structure. The exterior photo does show the details too well because of the small size. The more visible repaired portion indicates that some of the brick have been turned across the wall to provide the tie.

Since brick are available in many different sizes, measuring the length of the brick and the actual thicknesss of the wall will give you an idea of what width the gap could be. The construction of the wall (from the inside) is one brick thickness, a mortar joint (usually 3/8") and one brick length. Compare that to the actual wall thickness to determine what the gap could be. If those are traditional modular brick (usually 3 5/8" thick and 7 5/8" long) and the block are 8" block (actually 7 5/8" thick) the wall would be 11 5/8" thick with a 3/8" gap. If the block are 6" (5 5/8" thick) the wall would be 9 5/8" thick. Usually in residential construction the 3/8" collar joint is not filled with mortar. If the block are 4" (3 5/8"), the thickness of the wall would be 7 5/8" and the collar joint between the block and brick would be filled solid.

I understand you appearance reasons to for not using exterior insulation to maintain since you want to maintain the traditional SE Ohio appearance. Actually, the location of the insulation on the exterior is critical in the performance to take advantage of the thermal mass. This is why the thermal mass of solar heated and cooled homes is inside the insulated envelope. The last professional to put the insulation on the inside is still committed and is awaiting a petitioned release from the mental institution after years of confinement.

When selecting the interior wall insulation system, think about the electrical wiring method and space required. Do not forget the vapor barrier and avoid fiberglass if at all possible for space reasons and long term insulating value.

Good luck.


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