Insulating Basement Walls

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  #1  
Old 01-09-05, 08:25 AM
chopper33
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Insulating Basement Walls

Hello,
I have questions about insulating my basement walls. Our home is 4 years old and I am finishing the basement. The wiring is all but complete. The posts I have read on this site about insulating and using a moisture barrier are kind of opposing. Some say to use poly directly on the poured cement walls before the 2x4 studs go up and then again over the top of the insulation before the sheet rock goes on? Can you give me the real skinny of this? I have applied 1 thick layer of drylock to the basement poured cement walls already. Do I also need to put poly between the studs and the wall? It seems to me that this would trap any moisture that may come through the walls?
I was thinking of using un-faced R-13 batts of insulation and using a poly between it and the sheetrock. What is the advantage of using Kraf faced insulation when you are going to put poly between the insulation and the sheet rock anyway? How thick of poly is needed for this?
I also read somewhere that there should be a gap between the poured cement wall and the studs/insulation? How much of a gap is needed? I have a very small gap which varies between 1/8" to 1/2" or more. Anyway, how would you ensure that the insulation does not come in contact with the poured cement walls after installing it? Seems impossible to me... But then again I am not a carpenter by trade... Any advice?????

Thanks,
Chopper
 
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  #2  
Old 01-11-05, 12:54 PM
rluzinski
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This is basically my exact situation as well. I Drylocked the poored concrete walls and my studs are just barely not making contact. I bought Kraf faced insulation and a 4 mil plastic sheet (to be put on just before drywall).
 
  #3  
Old 01-11-05, 03:12 PM
chopper33
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Post But how?

But how do you ensure that the insulation batts are not in contact with the foundation walls after it is installed? Seems just about impossible? Do you need the Kraf faced insulation batts as opposed to non-faced insulation batts? I was thinking just becuase I am going to put poly over the top of the insulation prior to drywall or other materials.
 
  #4  
Old 01-11-05, 06:54 PM
rluzinski
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I guess I never realized that it was imperitive that the insulation NOT touch the wall. I got the faced insulation but that faces toward teh interior anyway. I have a new home with poored concrete basement walls. I taped aluminium foil to the wall for a week and found no condensation underneth afterwards. That was before I sealed them. Maybe I am being to optimistic?
 
  #5  
Old 01-12-05, 07:07 AM
123456
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I have a similar situation. My basement is poured concrete walls that are 4 years old. We are in the planning stage now, so we want to do it right from the beginning.
I am hoping you get some good response to this thread!
 
  #6  
Old 01-12-05, 07:22 AM
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Originally Posted by chopper33
But how do you ensure that the insulation batts are not in contact with the foundation walls after it is installed? Seems just about impossible? Do you need the Kraf faced insulation batts as opposed to non-faced insulation batts? I was thinking just becuase I am going to put poly over the top of the insulation prior to drywall or other materials.
It's quite simple, the more you move away from concrete the less of a chance of anything touching that wall - consider at LEAST 1 inch. Also, you can staple plastic strapping around the back side of the studs to make sure insulation does not expand beyond a certain point. Or you couls use spring rods to keep it in place, they'll compress it somewhat though. Don't sweat the small stuff, a strand or two of fiberglass will come in contact with the wall, but it is not a big deal, what you don't want is a big contact patch. And if you are going to hang poly over fiberglass, you don't need the Kraft facing. Good luck
 
  #7  
Old 01-12-05, 07:40 AM
Shadowman
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On the insulation, there's no need for kraft faced if you are putting poly up. It's just that some areas will sell mostly kraft faced so those people don't really have a choice. I used 6 mil poly.
 
  #8  
Old 01-12-05, 11:58 AM
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I have also seen a product out their that I don't recall its name but its bubbly on one side and sommoth on the other when i say bubbly I mean like the bottom of a soccer shoes that is placed on the wall and if water gets to it then they are lead to the bubbles unit they are at the bottom were maybe and hopefully the drainage are.
 
  #9  
Old 01-12-05, 04:28 PM
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Different areas require different applications. In some towns and countries, they require plastic be draped over masonry walls before insulating. This would suggest a high water table and/or low frost line. Everyone should check with their local bulding inspector's office for code requirements.

The gap between the insulation and masonry wall is known as a drainage plane. These are applied because of the difference between the moisture absorption and expulsion rate of the insulation and the masonry. Fiberglass insulation has a slow absorption and a fast expulsion rate to moisture, whereas masonry has a fast absorption and slow expulsion rate to moisture. Air also has the ability to absorb and expel moisture. In a Dead Air Space (drainage plane) gives it the ability to make up for the difference between the two materials, thereby creating balance. Which is the best term to describe nature.
 
  #10  
Old 01-12-05, 06:44 PM
chopper33
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Smile Great explanation

Resercon,
Wow, what a great explanation! I already have my stud walls up and they are not going to be easy to now move them further away from the foundation walls. If I already have dry-locked the walls, do I still have to worry about the insulation coming in contact with them? If I were to stapel plastic strapping to the studs to keep the insulation away from the walls, where would I get such a thing and what do I ask for at say Home Depot? How many straps are needed per every 16" x 8' stud space? Seems to me that if I don't have much of a distance between the studs and the foundation walls to begin with that even if I put straps up that the insulation will bulge and come in contact with the wall between where the straps are installed. Would a simple solution be to take a thin layer of insulation off each batt prior to installation to make the seperation from the insulation and the foundation wall greater?
I am hoping to clear up some great confusion on this thread! Thanks everybody for the input!!!!!
 
  #11  
Old 01-12-05, 07:50 PM
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Installing the strapping is impractical. You are better off using a less thick insulation to provide the separation. This is very important in your situation because of the Dryloc. Basement water proofing prohibits moisture flow in both direction (in and out of the basement). The drainage plane will reduce the probability that the moisture in the heat that manages to get through the insulation does not condense.
 
  #12  
Old 01-12-05, 08:26 PM
darren_1974
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You could put rafter vents in between each stud. I know they make some thin ones. They are made of styrofoam and are usually very cheap. They'd keep the fiberglass off the concrete
 
  #13  
Old 01-13-05, 07:01 PM
chopper33
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Question Another question

Resercon,
[Qoute] "Installing the strapping is impractical. You are better off using a less thick insulation to provide the separation. This is very important in your situation because of the Dryloc. Basement water proofing prohibits moisture flow in both direction (in and out of the basement). The drainage plane will reduce the probability that the moisture in the heat that manages to get through the insulation does not condense."[Qoute]

If this is the case, why do people waterproof there basement walls???? Do they make insulation in different thicknesses or would I have to pull off a layer of insulation off of each batt? Would it then be better to buy kraft faced insulation so I can staple the facing to the face of the studs to ensure that the batts are held in place and they won't get displaced and come in contact with the foundation walls? This is kind of stressing me out a little having to worry about mold problems happening if I do this wrong.... Thanks for the ideas this far!
 
  #14  
Old 01-13-05, 08:30 PM
AFH_98
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Smile I need similar help and advice!

This website/forum is awesome!

I am getting ready - I should say early planning stages - to remodel my basement. Currently, it has paneling up around all of the block walls using 1X2's. No insulation or vapor barrier, and the block walls are bare. It was that way when I bought the house. I am going to tear all that out and was planning on painting/drylocking the block walls and then applying drywall.

What is the proper way of doing this? From what I've read, I need to make sure nothing (including the frame/furrier strips) touches the block wall, and insulation is a must along with the vapor barrier.

In what order should these be? I am guessing drylock, frame & insulation, vapor barrier and then drywall. Is that a correct assesment? Any tips or suggestions? Thanks in advance!
 
  #15  
Old 01-13-05, 09:18 PM
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http://www.eere.energy.gov/consumeri...heets/bd4.html

This site discusses Vapor Diffuser Retarders (VDR) better known as Vapor Barriers. It also discusses Thermal Moisture Dynamics. It does explain that in different climate areas, vapor barriers are installed differently and in some cases, not even recommended. However, it applies to above grade applications. Basements are below grade applications and different factors come into play. I strongly suggest to everyone to check with their local building code officials what are the requirements for their area.

The drainage plane or Dead Air Space between the insulation and the masonry wall is considered a buffer zone. An added feature to prevent a possible moisture problem. For example. let's say there is an exit ramp on a highway. Due to accidents at the end of the ramp, a traffic light is installed. During most of the day, this doesn't pose a problem. However, during rush hours, traffic backs up onto the highway because of the traffic light. To prohibit the traffic backup onto the highway, the exit ramp is extended and widen to two lanes. The result is the traffic does ot backup onto the highway anymore during rush hours.

Here the cars represent moisture in heat, the exit ramp represents the masonry wall, the traffic light represents the basement water proofing, the traffic backup represents condensation and the extending and expanding of the exit ramp represents the Dead Air Space.

Does this mean if you water proof your basement and do not have a dead air space, will you have a moisture problem? The answer is NO. What it does mean is that it reduces the probabilty for a moisture problem to occur. Just like in the example, the determining factor was rush hour. In your basement, it is the amount of moisture generated inside the basement that is the determining factor. So if you do not have the drainage plane (dead air space), learn how to control the moisture generated in the basement.
 
  #16  
Old 01-14-05, 03:28 PM
chopper33
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Another great explanation

Resercon,
You are a Shakespeare at describing problem/solutions. Thanks for all the advice. The moisture thing seems to be a science in itself. The questions I am still curious about is from a prior posting here:

Would it be better to buy kraft faced insulation so I can staple the facing edges to the face of the studs to ensure that the batts are held in place and they won't get displaced and come in contact with the foundation walls? I assume that I don't need poly if I am using kraft face insulation?

AFH_98, I hope this set of threads helps you as it is helping me

Thanks a bunch,
Chopper33
 
  #17  
Old 01-14-05, 03:35 PM
chopper33
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Please also see the last post...

Resercon or whomever finds this thread,
Maybe a dumb question after all of this but here it goes... Correct me if I am wrong that on Kraft faced insulation, the Kraft facing should be towards the interior of the basement instead of facing towards the foundation walls?
The reason why I am asking is that I read the opposite was being confirmed somewhere else on this site?
Thanks!
 
  #18  
Old 01-14-05, 05:08 PM
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You are correct, the Kraft faced insulation should be between the insulation and the interior of the basement. So from the basement wall, the insulation, Kraft face (vapor barrier), sheet rock.

This is the norm when heating is being used in basements. Nonetheless, under certain conditions, the vapor barrier may face the foundation wall. This situation is usually enforced by building code and every store that sells insulation is aware of the code because it deviates from the norm. I doubt very much if you area requires it, but just to be sure, I would recommend contacting your local building officials.
 
  #19  
Old 01-14-05, 05:51 PM
rluzinski
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Great link, Resercon. In part it said,

"A good rule to remember is: To prevent trapping any moisture in a cavity the cold-side material's Perm rating should be at least five times greater than the value of the warm-side"

By greater do they mean higher or better at stoping vapor (lower perm rate). I would assume they mean a higher perm value, which would make sense.
 
  #20  
Old 01-14-05, 08:15 PM
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You are correct, the lower the Perm Rating, the least amount of moisture will penetrate the material per hour. The higher the Perm Rating the more moisture will penetrate the material.

It is good to note that most professionals and manufacturers use a material of 0.1 Perm Rating for vapor barriers. We do this to avoid violating the 5 to 1 rule.
 
  #21  
Old 01-15-05, 03:55 PM
mr three putt
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Before you insulate your basement, read this artcicle. It has lots of useful information:

http://www.eere.energy.gov/buildings...s/db/35017.pdf
 
  #22  
Old 01-17-05, 05:47 PM
rluzinski
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Well I put a cement sealer on very thin on 2 of the four walls, so I don't think i will be breaking the 5 to 1 rule. I got a 4 mil vapor barrier, is that most likely .1 perm (probably depends on the type, huh)?

For the walls I have no sealant and a 1" buffer, per our guy resercon's instructions.
 
  #23  
Old 01-17-05, 06:04 PM
rluzinski
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If I'm reading that link correctly, doesn't it recommend not installing a vapor barrier to the interior of the wall of any kind? Kind of tough for me to do, since code requires it. I'm pretty much to the point of not even caring anymore. Noone can seem to agree and while I fully respect the linked report, if my own state doesn't respect it, what can I do? In the report they admitt the code requirements in Min (vapor barrier on both sides) is the WORST thing you can do.

Is faced insulation considered a vapor barrier?
 
  #24  
Old 01-20-05, 02:51 PM
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Insulated Panel System

I'm thinking of doing my basement also and recall seeing somewhere (TV, magazine) a wall system for basements that was an insulating panel with a durable covering on the inside face that was prefinished. Installation was done by gluing on the wall with construction adhesive...am I dreaming or does this exist? I've done a search of the internet and can't find anything.
 
  #25  
Old 01-20-05, 05:04 PM
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Corning makes such a system but they do not glue it to the walls. I heard that it is very expensive.
 
  #26  
Old 01-24-05, 09:18 AM
Stickman
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The Corning system looks great but you are right it is very expensive and not a DIY, you have to go through an approved installer. But they do have a basement wall insulation system that is easily installed.
 
  #27  
Old 01-26-05, 06:16 PM
MylesOC
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So, I've been reading through a few of these threads, and from what I have researched (DOW, Owens Corning and Building Sciences websites) is that any studded wall with fiberglass insulation, vapor barriered on the warm side, moisture barriered on the cold side will inevitably fail. Now, I don't mean like the sky is falling (chicken little).... it may be fine for years, but from what I've read is that all vapor barriers cannot be perfect, and eventually allow enough warm moist air to penetrate through to the cold concrete surface, condense, and become a mould breeding ground. What everyone is saying, is if you don't have an ICF foundation, or external rigid insulation, you effectively need an expanded (good) or extruded (better) poly styrene foam firmly attached to the interior of your concrete walls. (ie: the closest thing to an interior retro-fit of an ICF foundation).

There will be 2 sources of moisture in your walls:
1) ground water penetrating the concrete through the exterior (including capillary action up through the footing)
2) water vapor in the interior air, which will condense if it comes into contact with a cold surface.
What I've found, is to prevent #1, you should have an exterior rubber membrane installed at build time. If you don't have that, you have to accept some water penetration through yoiur walls. The last thing you want to do is trap that. it will not dry to the exterior, below grade. (it will dry to the exterior above grade). This is why I've seen the moderator describe this space that is required between your wall and studs/insulation. Or, I understand you could use a rigid insulation tightly strapped to the walls (ie: no air space) and allows some permeability (ie: a type 1 expanded or type 2 extruded with a perm >= 1.5). It's properties will not be affected by the moisture. You then want your foam to be able to "breath" and releast moisture vapor to the interior, which must be able to get through a drywall and "latex" (not alklyd paint) panel. If you put vapor barrier behind the drywall or panel, you're again trapping water where you don't want it to stay or build up.
To deal with moisture problem #2, Ideally you insulate from the outside before you backfill. Not having that, you could insulate the interior with a completely uniform (no holes, or cracks) insulated foam covering of your walls, including your top ledge, and rim joist. This essentially eliminates the possibility of a cold surface coming in contact with interior air. It means you need to seal all the foam joints, and ensure it's held securely against the wall. You also have to deal with how you run your wiring etc..., and it's recommended to lay 2x3 strapping flat on top of the foam, which gives you at 1.5" depth to put shallow elec boxes and wiring without having to cut recessed holes in the foam. You can also then insulate with another layer of 1.5" foam between the strapping and cut around the elec boxes.

I know this is a long ramble, but anyone see any problems with this? I'm in the starting stages right now.
 
  #28  
Old 01-27-05, 12:07 PM
123456
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I think that I have come to a similar method as you have (if I understand you correctly!)
I do have a rubber coating and rigid insulation on the exterior of my basement walls, so I don't want a vapor barrier on the inside.
I am leaning toward putting EPS foam on the inside basement walls (no vapor barrier in that foam right?) and then putting 2 x 3 strips over the foam, then drywall.

Is this an acceptable method?
Do you tapcon the strips to the concrete wall in this situation?
Does that present a problem with the foam between the strip and the wall?
Do you keep the foam up off of the floor (an inch like the drywall) or put it all the way down?

Thanks
 
  #29  
Old 01-27-05, 05:45 PM
mr three putt
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"Ideally you insulate from the outside before you backfill. Not having that, you could insulate the interior with a completely uniform (no holes, or cracks) insulated foam covering of your walls, including your top ledge, and rim joist. This essentially eliminates the possibility of a cold surface coming in contact with interior air. It means you need to seal all the foam joints, and ensure it's held securely against the wall. You also have to deal with how you run your wiring etc..."

I wonder if one of the spray foam options (such as icynene) would be feasible for a renovation? Couldn't one simply frame the exterior walls, run the wiring, and then spray foam it? It's a little more expensive, but it is fast, easy, and completely seals.
 
  #30  
Old 01-28-05, 09:20 PM
MylesOC
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123456: I'm certainly not an authority, but have researched the crap out of this. I think it's important to understand that the vapor barrier on the interior is not directly related to having an external rubber membrane on the outside, nor having external insulation. However, I believe the external insulation (including above grade, up to your siding) does dramatically decrease the possibility of condensation/moisture on the inside of your foundation walls. The rubber membrane also should prevent external ground source water from penetrating into your foundation walls. However, you will still have humidity inside your basement, and with warm air, needs to be managed. With what you've done on the exterior, and using rigid EPS on the interior, if you completely cover your concrete with this insulation, I don't believe you need any vapor barrier. I'm starting mine tomorrow, and that's my plan.

As you indicate, I too am drilling my 2x3 strips into the concrete (and through the foam) with 4.25" tapcons. By countersinking them .25", I should get them a full 1" into the concrete. I have a hammer drill, and lots drill bits to pilot them. I think this is the best way, so that the foam is held tight against the concrete between it and the strips as you describe. I'm also running a heavy bead of acoustic caulk along the tops and bottoms of the foam and concrete and taping all joints. I'm going to have the foam right down flush with the floor, but keeping the drywall 0.5" up off the floor.

Mr threee putt: yea, I haven't looked into those spray foams, but there are a few out there. Sounds like the easiest plan to me, especially if you have an any unevenness in your walls. It looks great for hard to reach areas too (e.g.: all around the rim joist and box joist cavities at the top ledge of the concrete walls. I bet it would also seal-up any cracks in those areas too.
 
  #31  
Old 01-31-05, 01:42 PM
123456
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Thanks MylesOC- We hope to start soon too...Hope it all goes well for us both
 
  #32  
Old 02-02-05, 11:50 AM
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That's EXACTLY what I recently did... almost. I used construction adhesive to attach 2" polystyrene foamboard to the foundation walls (R13). The only difference being is that I studded the wall out and put blocks of wood between the studs and the insulation so that it was nice and snug. I ran into an issue that maybe you can help me with. The rigid foamboard is just that... rigid. And sometimes it doesn't fit plum against the wall... this stuff will NOT bend. This mostly happens at the top of the concrete wall. What I did was use thin, rolled foam to fill in the gaps. I also taped the seams. I fear that this may not be enough, however. What do you think?

Other than that, I'm very pleased with it's application in my basement.
 
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