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Our unfinished basement has hollow cinderblock walls and I am wanting to insulate it and drywall the basement. Our house sits on a slope so the font of the house, including the basement, is ground level, but the backside is underground. What is your recommendation for insulating it? The house is located in North Alabama. I have YouTubed a few different methods of insulating. Option A: 2" rigid foam board, then 1 x 4, and finally sheetrock. Option B: 1/2" and 3/4" rigid foam board, air gap, stud wall with 2 x 4, then roll fiberglass insulation, vapor barrier, and finally sheetrock.

Option A seems like a good option for the back part that is underground to maximize the space but on the front part of the room, I feel I need to utilize option B since it is an exposed hollow wall. Attached is a picture to help describe the situation of the basement. enter image description here

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    Did you look around the Home Improvement site for other discussion threads? I know I've participated in several over the past couple of months. Here's one: diy.stackexchange.com/questions/182977/… – SteveSh Feb 6 at 12:33
  • Unfortunately your question is both broad and opinion-based, both of which make it off-topic here. both are viable options, but you will need to decide what cost, R-value, and effort level are appropriate. – isherwood Feb 6 at 14:38
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    This covers a lot of topics and techniques: buildingscience.com/sites/default/files/migrate/pdf/… – DaveM Feb 6 at 17:40
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    I have to add another topic, if you finish the area you will need outlets every 12’ or no space more than 6’ away from one. So you need enough space to put boxes in the walls, unless you want surface mount boxes and conduits on the walls. I like the wiring to be concealed. – Ed Beal Feb 6 at 18:20
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I don't know that there is a "perfect" way to insulate basement walls. When I built my house, 40+ years ago I did this:

  • outside layer of foam board
  • mastic (tar) on outside of block
  • inside wall, 6 mil vapor barrier, taped
  • fir studs, with high R board
  • drywall

I have not had moisture problems, but mileage will vary.

One's biggest concern will be heat loss, and moisture. One wants the moisture away from wood and drywall, and at the same time, one wants reasonable insulation. Alabama does not get the cold that we do up north, so that will make moisture control easier. If air flows over a cooler surface, it can condense if the surface is at or below the dew point of the air. Since the temperatures and dew point will vary in a house, it is desirable to have a good spread to assure dry materials.

While I am not endorsing either option A or B, I am pointing out that your strategy must address moisture management, and then more obviously heat loss. Not managing the moisture has the likelihood of being more expensive, should you have to replace materials and re-mediate mold after a few wet seasons.

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  • This house is about 40 years only as well. About 6 years ago water ingression was a real problem but the previous owner had a weeping wall installed with a discharge drain on the backside. Before we do anything I will seal the block with a water cinder block sealer to be safe. From that, I hope I can decide on a path that is most effective in moisture mitigation and insulating the home. It sounds like you did, with more detail than I outlined, option B from your description. Thank you for your input! – Roberts2600 Feb 6 at 17:09
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    Part of my success was location...at the top of a knoll. Also, not in your question, but I did a bit of planning in my basement and put 6 mil plastic (and more insulation) under the slab. That and the protections on the wall have helped keep the basement bone dry, free of visible mold. If you decide to put in flooring, use a vapor barrier on top of the concrete, the, fir up, and leave high R insulation under the floor. – mongo Feb 6 at 18:23
  • I had not considered fir up (raising the floor) to add some R-value and help keep the room warm. I will have to research this and might have some follow up questions later. – Roberts2600 Feb 10 at 12:47

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