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Old 03-03-2013, 03:41 PM   #1
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Insulation (floor underneath crawlspace)


Hey guys,...My kitchen was an addition (Crawlspace underneath) and the floor gets cold as ice in the winter. I'm thinking of putting some batting between the joists in the crawlspace area. But what side would the paper be facing? My guess is the warm side but then I'd have raw fiberglass hanging down. Not sure how I would attach it too. Doesn't seem right. Any suggestions?

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Old 03-03-2013, 03:55 PM   #2
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Insulation (floor underneath crawlspace)


#1 go back and add your location to your profile.
#2 There needs to be a 6 mil. vaper barrier on the ground first.
#3 The rim joist needs 2" blue foam and air sealed with expanding foam.
#4 Any holes in the floors from plumbing or wiring also need to be air sealed with the foam.
Paper goes toward the conditioned surface.
Depending on your joist spacing you use 16 or 24" insulation hangers.
http://www.bing.com/images/search?q=...lectedIndex=24

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Old 03-03-2013, 04:07 PM   #3
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Insulation (floor underneath crawlspace)


How far are the floor joists off the ground?

My suggestion: if you're laying on the ground looking up at the bottom of the floor, install fiberglass batts with the paper side TOWARDS the heated surface. In this case it would be plywood. At this point you will have exposed fiberglass to the elements. By elements I mean rodents who would love to rip the glass to shreds and make nests out of it.

You can plastic over it but it's not recommended...this will trap moisture and create a huge mess. My suggestion is to use Dow board (foil faced ridgid foam board that come in 4' X 8' panels and in 1/2", 3/4" and 1" thicknesses) and install that over the joists to hold and cover up the fiberglass. Between every panel you just need to leave some gaps to allow for air flow. You may also want to drill a few air holes as well.

To secure the Dow board use button head or cap head nails!

If you forget about the insulation, remember this: heat transfers from hot to cold. In the winter the outside wall is cold, your house is warm/hot and where the two meet, the air condenses! the paper facing on the insulation essentially "prevents" this condensation or keeps it on the warm side so it can then evaporate!

Hope this helps!
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Old 03-04-2013, 10:53 PM   #4
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Insulation (floor underneath crawlspace)


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Originally Posted by DIYChick45
Hey guys,...My kitchen was an addition (Crawlspace underneath) and the floor gets cold as ice in the winter. I'm thinking of putting some batting between the joists in the crawlspace area. But what side would the paper be facing? My guess is the warm side but then I'd have raw fiberglass hanging down. Not sure how I would attach it too. Doesn't seem right. Any suggestions?
Google Building Science and then search for crawl space insulation. They recommend insulating the rim joists with foam boards, closing any vents, and treating the crawl space as part of the interior. That way you will reduce the chance of having condensation down there and your floors will be much more comfortable. I followed their recommendations and my crawl space now averages 63-65 degrees all year. Possibly no need to install insulation under floor either.
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Old 03-04-2013, 11:56 PM   #5
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Insulation (floor underneath crawlspace)


In Ohio, the paper facing goes toward the warm-in-winter= up. In a cooling climate,(eg. FL) warm-in-winter is down. If you go with PIC, the foil is the vapor barrier, tape the seams w. foil and don't put holes in it; http://www.buildingscience.com/docum...n-crawlspaces/ If the foam is thick enough for your location, you won't need asphalt paper-faced batts with old style floor boards for sub-floor. If they used plywood/OSB for sub-floor, it has a low vapor perm rating similar to paper-faced.
If you close it off by insulating the walls, then follow through and condition it with an air supply per code; http://www2.iccsafe.org/cs/committee...E_06_64_07.pdf

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Old 03-20-2013, 09:00 AM   #6
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Insulation (floor underneath crawlspace)


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Hey guys,...My kitchen was an addition (Crawlspace underneath) and the floor gets cold as ice in the winter. I'm thinking of putting some batting between the joists in the crawlspace area. But what side would the paper be facing? My guess is the warm side but then I'd have raw fiberglass hanging down. Not sure how I would attach it too. Doesn't seem right. Any suggestions?
I re-did my crawl space about two years ago. My Kitchen, Dinning, and Living room is over a crawl space and I felt the rooms were very cold. I added XPS Foam board to the crawl space foundation and sealed the seams with proper tape. Secured the board with a combination of adhesive and also bolts with large washers. I then added insulation between the joists. I used Roxul, I can't stand fiberglass, but that's just a personal preference. I spray foamed the sil ledge filling up gaps that were letting air in. I also sealed the rim joists which were a big culprit for letting air in. I cut the XPS foam board to fit and sealed edges with spray foam. I sealed up any electric, cable, etc.. holes with spray foam as well as any gaps around venting. I finally added a proper vapor barrier to the dirt floor and taped. I noticed a nice difference and I feel comfortable knowing what's down there is done right and the air I am breathing is much healthier. I keep a wireless temp and humidity gauge down there along with a dehumidifier which runs in the summer time.

I think a place to start is adding some insulation between the joists and air sealing the crawlspace. Air sealing is probably best think you can do, stop that cold air from getting into your crawlspace will help allot. Good luck
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Old 03-20-2013, 11:57 AM   #7
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Insulation (floor underneath crawlspace)


@ cbaur. Glad you see the difference in your project, but you probably did too much in foamboard on the walls and insulation in the joists as well as an airseal. If your vents are open, you are probably not seeing much ROI on the foamboard on the walls.

@ OP. Rim joists and airsealing are going to make a big difference in your climate control in the room, but your issue is with conduction, not convection. Now, you HAVE to airseal to see the full effect, but decide where first. if you want to do foamboard around the walls, seal any penetrations to the outside, along with the perimeter, and install at least a 6 mil vapor barrier that runs up behind the foamboard. No need to foamboard the wall that connects the addition to the basement.

If you decide to address the floor directly, seal the perimeter, any penetrations in the floor, and any connections the crawlspace has to the basement. Apply your batts to the floor, and foamboard the connection wall to remove the crawlspace from the envelope.

If you have ducts or water lines in this area(I would assume you do as its the kitchen) the first option is the way to go. If not, the second is your best bet. No sense in heating and cooling the extra footage for no purpose.
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Old 03-20-2013, 01:10 PM   #8
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Insulation (floor underneath crawlspace)


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@ cbaur. Glad you see the difference in your project, but you probably did too much in foamboard on the walls and insulation in the joists as well as an airseal. If your vents are open, you are probably not seeing much ROI on the foamboard on the walls.

@ OP. Rim joists and airsealing are going to make a big difference in your climate control in the room, but your issue is with conduction, not convection. Now, you HAVE to airseal to see the full effect, but decide where first. if you want to do foamboard around the walls, seal any penetrations to the outside, along with the perimeter, and install at least a 6 mil vapor barrier that runs up behind the foamboard. No need to foamboard the wall that connects the addition to the basement.

If you decide to address the floor directly, seal the perimeter, any penetrations in the floor, and any connections the crawlspace has to the basement. Apply your batts to the floor, and foamboard the connection wall to remove the crawlspace from the envelope.

If you have ducts or water lines in this area(I would assume you do as its the kitchen) the first option is the way to go. If not, the second is your best bet. No sense in heating and cooling the extra footage for no purpose.
@asinsulation, thanks for the info I appreciate it, however my crawl space has been converted to a conditional crawl. All vents have been sealed up and closed. I see small degree difference in the crawl space compared to my living space.
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Old 03-20-2013, 01:10 PM   #9
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As mentioned above, you either insulate and seal the floor from the crawlspace, or the crawlspace from the exterior. You don't do both.
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Old 03-20-2013, 01:11 PM   #10
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As mentioned above, you either insulate and seal the floor from the crawlspace, or the crawlspace from the exterior. You don't do both.
Unless it's a conditioned crawl
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Old 03-20-2013, 03:18 PM   #11
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Unless it's a conditioned crawl
No cbaur, that is not correct. You would not insulate/seal a conditioned crawlspace from the other living space. That is what asinsulation was correcting you on as well. You would either insulate and seal the crawlspace walls, making it part of the building envelope, or you would seal and insulate the crawlspace FROM the other living space, making it outside of the envelope.
Personally, I recommend the former. As they mention in the article, it should be treated as a "mini-basement".
http://www.buildingscience.com/docum...ace-insulation
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Old 03-20-2013, 03:22 PM   #12
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Insulation (floor underneath crawlspace)


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No cbaur, that is not correct. You would not insulate/seal a conditioned crawlspace from the other living space. That is what asinsulation was correcting you on as well. You would either insulate and seal the crawlspace walls, making it part of the building envelope, or you would seal and insulate the crawlspace FROM the other living space, making it outside of the envelope.
Personally, I recommend the former. As they mention in the article, it should be treated as a "mini-basement".
http://www.buildingscience.com/docum...ace-insulation
I won't argue with you I've done allot of homework on the subject years ago and that's what I came up and implemented. Its working very well for me and I notice a nice difference in my home.
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Old 03-20-2013, 04:06 PM   #13
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Insulation (floor underneath crawlspace)


its good that you do see the difference. but with the vents sealed and the outside properly insulated with a vapor, you are pretty much just storing the batt insulation in your crawlspace
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Old 03-20-2013, 04:09 PM   #14
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Insulation (floor underneath crawlspace)


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its good that you do see the difference. but with the vents sealed and the outside properly insulated with a vapor, you are pretty much just storing the batt insulation in your crawlspace
I really don't think so as there is a noticable temp difference down in the crawl space and I don't want that colder air coming up through the floors making the room feel cold especially with no socks on

No matter how much you insulate the walls it's going to still be a cold room. Not as cold as before but it's still going to be a cold space IMO.
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Old 03-20-2013, 04:40 PM   #15
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Insulation (floor underneath crawlspace)


yes, but the reason you have a temperature difference is because you have stopped the circulation into the crawlspace. which is fine for now. just that it will leave alot of potential for moisture issues in the future, and drying out your floors. same principle as somebody who insulates both the attic floor and the roof rafters in the attic.

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