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Old 12-05-2010, 12:43 PM   #1
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Crawlspace insulation

Hi. I just purchased a property that has a dirt damp crawl space under wood joyces. The floor joyces have r-13 fiberglass insulation with paper side down stapled to joyces. The paper side is completely deteriorated and looks like isicles of paper/insulation hanging down everywhere. What should I do to insulate this area? Is there still a benifit to save insultion and cover with another type? It is approx 2400sq ft.
Thanks Tim


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Old 12-05-2010, 02:02 PM   #2
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The first thing I would do is put a moisture barrier on the damp ground. Think I would then remove all of the old insulation and install the paper up with new insulation. They have wire holders that are made to hold it up between the joists.


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Old 12-05-2010, 04:40 PM   #3
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I agree. Yard the existing out. Along with it, you will probably be disposing of alot of rodent droppings, nests and maybe even some rodents themselves. Install the new vapor barrier directly over the exposed dirt and then the new insulation will not need to be faced with paper.

Make sure that your crawl space vents are unobstructed. Cross ventilation is important for a dry crawlspace.

Upgrade your crawlspace insulation to at least a R-21 ( depending on your region )

Wire rods are availabe and will hold the insulation into the joists cavitys. Some folks also use twine stapled onto the joists in a zig-zag pattern basically creating a "net" that holds or keeps the insulation from falling from the joist cavitys

The insulation will "friction fit" (almost indefinatly) into the cavitys and stay in place. The above 2 techniques just prevent the insulation from falling, or being pulled out by critters later on down the road. I mention this because I dont want you to feel as if you have to hold the insulation in place with one hand while trying to fasten with the other. Fastners, or I should say "preventers" are a must but they dont have to go in immediatly. Insulation install one day, and preventers the next
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Old 12-05-2010, 04:47 PM   #4
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Crawlspace insulation

Is there any value to the old insulation? If I flipped it and added r-13 under it, with the deteriorated side up, and no face on new, what would happen? A lot of work,I know. New r-19 cost is $1400. Could a layer of 3/4" prodex help? cost is about $1400 also,but I wouldn't have to remove old. I was worried about moisture in between. It would only add r-5. 1" would add r-6.5, but it would cost $1700. Blue 1" would add r-5 at a cost of 1200.
Lots of questions -TIM

Still deciding best way to insulate crawl space.
* I decided that I don't want to remove old deteriorated/torn paper side down insulation-(way to much work and mess).
* I'm thinking of stapling prodex 16" or 48" to joyces under r-13 old deteriorated insulation. (On crawl space it said I would only add r-6, but taped at joints and added to my deterioated insulation I thought it would get down on some cold going through floor. My cost would only about $1100 this way.
* I still would put a thick plastic on floor-(6mill )???
* And mayby a 3/4' silver sheet glued to dirty concrete wall r-5 -- or blue 1' foam with no foil at r-5 glued to wall. Would any or all of this work? My cost total would be around $2000
Thanks tim

Last edited by Tim Sommers; 12-12-2010 at 04:34 PM.
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Old 12-05-2010, 05:02 PM   #5
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What zone do you live in? One school of thought recommends plastic on the floor and insulation on the side walls. Also, the vents tend to be open in the summer when the air is at it's most humid, not that I advocate opening the vents in the winter instead.
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Old 12-05-2010, 05:09 PM   #6
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Yes Tim, there is value to the old. Use it if you are trying to save some bucks. The paper face you see should be facing the warm side of the structure. Any insulation helps

"If I flipped it and added r-13 under it, with the deteriorated side up, and no face on new, what would happen?"

Nothing but add a better R value. Faced insulation in the crawl space is not necessary. Definatly add the vapor barrier over the exposed dirt
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Old 12-05-2010, 07:46 PM   #7
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Paper side down may be correct.... In a radon zone, wait on laying the plastic... Check for your required crawlspace R-value....Faced insulation may be required in your local area......

1. Are there any vents?
A few points: “A radon mitigation system will require ventilation of the crawl space to the exterior. Not planning for radon-resistant construction may necessitate air sealing the floor to mitigate the radon through ventilation.
Ensure that combustion furnaces and water heaters located in the crawl space are sealed-combustion units equipped with a powered combustion system.”

2. Are there any heating/cooling units or ducting down there?

3. Location?
“Cover the insulation with a house-wrap or face it with a vapor barrier. The orientation of the vapor barriers depends on the home's location or climate. In most of the country, the vapor barrier should face upward. However, in certain regions of the Gulf states and other areas with mild winters and hot summers, it should face downward.

Install a polyethylene vapor retarder, or equivalent material, over the dirt floor. Tape and seal all seams carefully. You may also cover the polyethylene with a thin layer of sand or concrete to protect it from damage. Do not cover the plastic with anything that could make holes in it, such as crushed gravel. Be sure the headroom of the crawl space meets local code regulations if you are considering pouring a concrete slab.”

Another option:



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