Insulating Basement Block Walls
#1
02-28-03, 01:33 PM
Insulating Basement Block Walls
IN A PREVIOUS THREAD DOUG ALESHIRE SUGGESTED TO ADHESIVELY APPLY CLOSED CELL FOAM TO WALL PRIOR TO STUDS TO ACT AS A VAPOR BARRIER. IF THE FOAM IS TO ACT AS THE VAPOR BARRIER THAN WHY WOULD YOU NOT TAPE TO THE SEAMS AND TOTALLY ENCASE THE BLOCK. AIR COULD INFILTRATE UNTAPED SEAMS COULD IT NOT?
#2
02-28-03, 04:02 PM
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daleg,
I hope this helps you out with your question. First, rigid used below grade is only for purposes of adding additional insulation. As with a roll or batts, you can use kraft faced or not. Where you use the vapor barrier or tape is another matter. If you look at the below article that I made up. Alternative #2 is stating to use rigid panels - 4x8 which can be tongue and groove or not. I stated that you do not have to tape the seems since we want any condensation that forms be able to BREATH and DRY. Taping the seams would not allow for this to happen with potential problems to follow if you did this. The issue here is condensation of moisture, not the issue of air infiltration. The 1 inch gap in traditional framing is to allow for ventilation, it doesn't take away the insulation quality but protects against mold and mildew issues. If the rigid is used above grade, exterior, I would have to agree that taping seams would be a good idea and in fact is recommended by the manufacturer. I continued to say that you would construct your traditonal wall framing and use your vapor barrier either via kraft faced insulation or 6 mil. This is your choice.
"I guess this is the best and most economical way to construct walls that would be placed on the exterior. I prefer to see 2x4 but as mentioned by others they can get 2x3's. You still need that W/T plate. Doing the framing 16" O.C. provides a solid base for your 1/2" drywall. If using traditional framing method, frame your new wall 1" from the vertical block/masonry surface if using R-13. The reason to keep the wood out from the walls is the moisture that could damage them. If using insulation like R-19 and only 2x4 studs, the insulation would touch the walls. I have stated before that if a homeowner did put thicker insulation in, and the wall was only 1" from the masonry surface, I have recommended hanging a vapor barrier between the back of the wall and masonry surface. This doesn't allow for the insulation to touch the wall and air movement is not restricted but at least you won't create damage to the insulation or wood. If you do want to increase the R value, move the wall out further or use the R-13 and then apply a rigid insulation over the studs (warm side) then drywall (not paneling) *Code advises a 15 minute fire rated material over any rigid insulation - 1/2" Drywall*..
Kraft Faced insulation is fine to use in the above scenario. No need for the poly and you can do everything easily. You may find this easier and I would do this versus unfaced and vapor barrier because I don't like to play with it any more than I have to.
Let me add one other thing, rigid insulation used on a concrete/masonry surface is fine. Considerations to make in using this is;
1. If you are just using 1 1/2" rigid and furring strips - A. You need W/T strips to protect the wood. B. The strips can be adhesively applied but they must be solid - mechanical anchors may have to be used to insure that if shelving is installed it will hold. Problem with this is, the penetration into a sealed concrete/masonry surface is damaged and subject to leaking. C. Any electrical boxes will have to be shallow - sometimes makes it hard to wire. D. You must use a fire retardant material over this as per Code.
(Most books, articles about rigid and furring strips fail to say anything about the use of W/T and this will get destroyed and be a good source for mold/mildew with the slightest hint of moisture)
2. Alternative which does add cost is to apply full rigid sheets to the concrete/masonry walls, adhesively applied, then place frame wall against the rigid, then insulate between studs, apply 6 mil vapor barrier if applicable, and cover with drywall. The Rigid insulation does then act as a the vapor barrier. Do not tape/seal the seams. This allows it to breath and dry up any condensation that may form"
Hope this helps!
I hope this helps you out with your question. First, rigid used below grade is only for purposes of adding additional insulation. As with a roll or batts, you can use kraft faced or not. Where you use the vapor barrier or tape is another matter. If you look at the below article that I made up. Alternative #2 is stating to use rigid panels - 4x8 which can be tongue and groove or not. I stated that you do not have to tape the seems since we want any condensation that forms be able to BREATH and DRY. Taping the seams would not allow for this to happen with potential problems to follow if you did this. The issue here is condensation of moisture, not the issue of air infiltration. The 1 inch gap in traditional framing is to allow for ventilation, it doesn't take away the insulation quality but protects against mold and mildew issues. If the rigid is used above grade, exterior, I would have to agree that taping seams would be a good idea and in fact is recommended by the manufacturer. I continued to say that you would construct your traditonal wall framing and use your vapor barrier either via kraft faced insulation or 6 mil. This is your choice.
"I guess this is the best and most economical way to construct walls that would be placed on the exterior. I prefer to see 2x4 but as mentioned by others they can get 2x3's. You still need that W/T plate. Doing the framing 16" O.C. provides a solid base for your 1/2" drywall. If using traditional framing method, frame your new wall 1" from the vertical block/masonry surface if using R-13. The reason to keep the wood out from the walls is the moisture that could damage them. If using insulation like R-19 and only 2x4 studs, the insulation would touch the walls. I have stated before that if a homeowner did put thicker insulation in, and the wall was only 1" from the masonry surface, I have recommended hanging a vapor barrier between the back of the wall and masonry surface. This doesn't allow for the insulation to touch the wall and air movement is not restricted but at least you won't create damage to the insulation or wood. If you do want to increase the R value, move the wall out further or use the R-13 and then apply a rigid insulation over the studs (warm side) then drywall (not paneling) *Code advises a 15 minute fire rated material over any rigid insulation - 1/2" Drywall*..
Kraft Faced insulation is fine to use in the above scenario. No need for the poly and you can do everything easily. You may find this easier and I would do this versus unfaced and vapor barrier because I don't like to play with it any more than I have to.
Let me add one other thing, rigid insulation used on a concrete/masonry surface is fine. Considerations to make in using this is;
1. If you are just using 1 1/2" rigid and furring strips - A. You need W/T strips to protect the wood. B. The strips can be adhesively applied but they must be solid - mechanical anchors may have to be used to insure that if shelving is installed it will hold. Problem with this is, the penetration into a sealed concrete/masonry surface is damaged and subject to leaking. C. Any electrical boxes will have to be shallow - sometimes makes it hard to wire. D. You must use a fire retardant material over this as per Code.
(Most books, articles about rigid and furring strips fail to say anything about the use of W/T and this will get destroyed and be a good source for mold/mildew with the slightest hint of moisture)
2. Alternative which does add cost is to apply full rigid sheets to the concrete/masonry walls, adhesively applied, then place frame wall against the rigid, then insulate between studs, apply 6 mil vapor barrier if applicable, and cover with drywall. The Rigid insulation does then act as a the vapor barrier. Do not tape/seal the seams. This allows it to breath and dry up any condensation that may form"
Hope this helps!
