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I have a government grant (2,440$) to insulate all of my exterior walls. The issue is, I cannot access them from the outside because I have a brick house.

My first guess was that I will need to take apart all the walls inside and insulate from there. The good part is, most of my walls are already pulled off or will be pulled off. I am replacing the current 3/8'' drywall with 1/2''.

What kind of material would be the best to insulate my exterior walls? I have a 28'x 40' house, will 2,440$ be enough? Also, if there's a better way of doing this than removing the walls, let me know.

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If you wish to preserve the brick exterior, you have the following options, depending on the wall construction:

  1. If you have a structural brick wall (e.g. multiple-wythe brick or brick veneer on block) then you will have to insulate the wall from the inside. This will entail applying rigid insulation board--either foam or mineral wool--over the inside of the wall, and then covering that up with drywall.

  2. If you have a brick cavity wall (e.g. brick veneer on the outside and structural brick or block on the inside) then you can blow water-permeable insulation like perlite into the cavity. You could additionally insulate this wall from the inside as per above.

  3. If you have a brick veneer on wood framed wall, then you'll need to insulate the stud cavities normally. You can use fiberglass batts, mineral wool batts, closed-cell spray foam, or dense-packed cellulose. All will be effective. One advantage to dense-packed cellulose is that you don't actually need to take down the drywall; you just drill holes in the top and blow in the cellulose. This could save you a ton of money if you haven't already removed the drywall. If you have to or plan to remove and replace the drywall anyway, my personal recommendation would be installing either mineral wool batts or dense-packed cellulose in the stud bays, covering the open stud bays with an additional layer of rigid mineral wool board, and then applying the drywall over that. An added bonus is that this will all but completely soundproof the house.

  • I have a brick veneer on wood framed walls. I was hesitant to use cellulose, won't it eventually find its way down to the bottom of the wall after a few years? Or is this why you call it "dense-packed" ? I would really rather just drill holes in the wall. – Alex Oct 3 '14 at 16:42
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    Yes, dense-packed cellulose won't settle like the loose stuff will. You've identified the major advantage to sense-packing a wall with cellulose: you don't have to remove any drywall! – iLikeDirt Oct 3 '14 at 16:47
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    Great. Thank you! Also I appreciate the comment with the other answer, very appreciated. – Alex Oct 3 '14 at 16:52
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The problems associated with insulating brick, block, or concrete walls vary depending upon environment, construction, and even sunlight. It is critical to get a proper assessment of the overall situation. This is an instance where money spent on a documented professional consultant is money well spent.

I have come behind DIY folks many times. Some of them did well but most threw dollars away, or worse, created far worse problems. When the Feds pushed for greater sealing of walls, it was soon discovered that the lack of adequate ventilation resulted in exterior paint bubbling, a reaction to vapor forming inside the walls, often rotting sheathing and studs. Mandatory additional room venting was required.

Cooking, showering, and just living creates enormous amounts of moisture that has to go somewhere. I have had success with batting interior masonry walls, leaving an air gap. In subterranean situations I have used brush on sealers. On both interior and exterior, even floors, to stop moisture intrusion in combination with employing venting methods. Often the introduction of a dehumidifier of a simple small fan will halt mold in corners. Remember to use vapor barrier paint under your finish coat. Great stuff.

There is more that almost 50 years of this work and a willingness to research has taught me. I can't emphasize enough the value of an expert for you.

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Your two options are going to be insulation batting or spray foam.

Batting is cheap, easy enough to do as a DIYer and will easily come in under your price tag.

The other spray foam is more expensive and typically requires professional install. There is a DIYer kit out there but I have never used them. Professional install you are looking at way over your budget but the DIYer kit is about $3k for your size of house.

  • Is spray foam a better insulator than the latter or are both similar? Either way I guess I have no choice but to take the walls apart using either method. Thanks! – Alex Oct 3 '14 at 16:41
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    Spray foam is a better insulator, but it has the following drawbacks: it is vapor-impermeable, very expensive, and highly flammable, especially during application, as it cures exothermically. Furthermore, it is rare, but some people develop spontaneous allergies to its toxic chemicals. If this happens to you, your house is uninhabitable. I honestly don't recommend it unless you have no other choice. – iLikeDirt Oct 3 '14 at 16:49
  • I have used the DIY kit that you refer to. It is labor-intensive, requires lots of prep (marking studs and drilling holes). But if you really plan and take your time, you can get a good outcome. Look at videos on YT to get a sense of it. When I did it, YT was but a gleam in someone's eye. – Buck Oct 4 '14 at 10:04

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