Cold Floors and Crawl Spaces

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Old 02-18-15, 08:37 AM
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Cold Floors and Crawl Spaces

So I am looking for some advice on insulating my crawlspace. Last year I applied 2 inch rigid foam board around the crawl space walls and used spray foam to seal the cracks. (Note there is no insulation on the underside of the floors, but rather I am trying to make the crawlspace a conditioned area)

However this winter the floors of my house are still quite cold, which means either I need more insulation in the crawl space or there are still areas that need to be sealed better.

I am wondering if it would make sense to purchase one of those DOW Froth Paks and spray a 1 inch layer over the existing rigid foam. Not only will this add an additional layer of insulation, but it should insure that all gaps are sealed.

This will probably be more expensive than buying another round of rigid foam and spray foam cans, but I have to imagine that it will be much easier and quicker than trying to cut to fit more foam boards in that crawl space.

Thoughts? Does this seem like a legitimate plan to help insulate the crawlspace?

thanks for your comments.
 
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Old 02-18-15, 08:38 AM
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Do you have any heat being pumped into the crawl space/what's the temperature in there?
 
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Old 02-18-15, 08:54 AM
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I do have duct work in the crawlspace but it only serves to move heat to other parts of the house, in other words there is no direct source of heat in the crawl space.

I do live in Michigan, and so temperatures are routinely below freezing in the winter. I have heated floors in one portion of the house, the thermometer indicates that the floor is 40 - 46 degrees when the heating element is off. (During the winter months of course).
 
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Old 02-18-15, 08:55 AM
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Also, what is the finish floor? A hardwood or tile is never going to be warmer than air temperature and that is generally 25-30 degrees colder than body temp.. If you are walking around in bare or stocking feet there will be a noticeable temp. variation.

Spraying a foam pack will help but look at some other issues first. Is the top of the foundation sealed and insulated as well as the rim joists?

Although there is a time and place for foam packs I have generally found them to be as expensive or MORE expensive than having someone come in and do it. You may also then have them give you a price to hit the underside of the floor with an inch or so which will help in keeping the floor above from conducting heat to the crawl.
 
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Old 02-18-15, 09:06 AM
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Insulation only slows the transfer of heat. Given enough time even a well insulated area will get cold. The only way to keep it warm is to add heat. The earth and house above will provide some heat but over time even the ground under the house will chill. Ideally you would insulate the floor (ceiling of the crawl space) with the water pipes on the heated side of the insulation and not try to keep the crawl space warm.

It sounds like you've insulated your crawl space well. How do you ventilate it? Crawl spaces were never intended to be conditioned space. They rely on good ventilation to let moisture escape and prevent mold and rotting of the wood structure.
 
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Old 02-18-15, 09:19 AM
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The finished floor is a combination of wood floors, and carpet. But even the carpet (with padding) is cold.

I do agree that I need to look at the rim joist as well. I am dealing with a stack effect in my house, and I can feel cold air being sucked up from around my baseboards from the crawl space. My plan was/is to use the froth pak to seal the walls of the crawl, ensuring that I cover any gaps in the rim joist from below, and later filling in the wall cavities with cellulose insulation via small holes in the interior wall, thus hopefully ensuring the rim joists are completely sealed.

Interesting that experience has been that it is cheaper to have someone do the job. I'd hate to send someone down there, as it's so tight of a space!

Pilate Dane,

Hmm I thought the latest school of thought was to make the crawl space a conditioned area. I can't imagine I will be able to pump any sort of heat source down there. Perhaps thought it would make sense to spray the sides of walls and the underside of the floor... why not? It couldnt hurt.
 
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Old 02-18-15, 09:43 AM
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Given enough volume, you should be able to get closed cell foam installed for around $ 1.00 to $ 1.20 per board ft ,(1 sq.ft. At 1" thick). DIY kits are usually going to run that much just for material depending on the kit size and you cannot always expect to get the yield they advertise.

If you have shoe molding at your baseboard, you can also look into removing that and foaming/caulking the gap that may be at that point. Also don't overlook the exterior of the house, you may see gaps along the bottom edge of the siding where it covers the rim joist that can be foamed/caulked as well.
 
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Old 02-18-15, 11:18 AM
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Yep, a little more insulation and a heating vent down there should make a difference for you upstairs.
 
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Old 02-18-15, 11:34 AM
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Air sealing and insulating that rim cavity is a must. Also, adding some heat down there will quickly improve the cold floors, just not practical until all sealed and insulated.

By conditioned, most homes do not try to bring that space up to house temperatures, call it semi-conditioned.

And as Pilot mentioned, you will need to plan on ventilating the space in the summer. if home is air conditioned then sharing a little does the trick. Outside air may not be the best depending upon your relative humidity.

As for bringing in someone to spray, with the small space and small job I doubt the price will be that low. They like doing a whole house and right now and after this winter I expect them to be very busy.

A case of caulking or canned foam with extension tubes (cans like a vertical orientation). The froth packs may work, but that should wait for warm weather. You could always try one pack in a convenient location to see how it works and how much coverage you get. A trick I rad on one forum was to mist the surfaces with water before the foam. I can dig that up if needed, but it increased the coverage a lot. Need to verify that technique wasn't unique to one product.

Bud
 
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Old 02-18-15, 11:39 AM
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It sounds like you have not done anything with the rim joists yet? If that's the case, I would definitely address those first. In addition to the fact that the lumber by itself is not significant, there are as likely as not gaps around things like the dryer vent, outdoor spigots, and anything else that passes through the rim joists. I did not see a vapor barrier on the soil mentioned. That would be my second step, although hopefully it is in place, because I would have run it part way up the walls, behind the insulation. I have seen significant benefit in caulking the exterior bottom plates as was mentioned too.
 
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Old 02-18-15, 11:52 AM
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I only know about my own area but the Washington State Energy Code requires that non-ventilated crawl spaces have a connection to the heating/cooling system of the house. They specify a minimum airflow through the crawlspace although off the top of my head I don't remember what that minimum is, I think it is a percentage of the total airflow of the system and is something like ten percent. To do this you need to have a duct discharging conditioned air near one end of the space and a return duct at the other end to ensure the majority of the space is "swept" by the flowing conditioned air. Obviously, in such a situation you want the entirety of the space sealed from the outside air.


Oh, as far as the DIY foam packs...they require a minimum temperature to use, best is above 70 degrees but they will work, albeit with a lower yield, at somewhat lower temperatures. They also require a learning curve as you have at best 20 seconds from the time you close the spray nozzle until the next time you open the nozzle. Wait too long and the foam hardens in the nozzle. They do come with several nozzles and additional nozzles are available to get around this problem. Learning just how much to spray and how fast to move the nozzle is part of the learning curve. Move to slowly and you will build up way more than necessary but move too fast and you won't get enough build. Not enough and you can go over again but too much is just wasted.
 
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Old 02-18-15, 01:24 PM
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Thank you for all the suggestions. Unfortunately, it is soo cold here in MI right now (-10 at night) that I don't think it's a good idea to be doing anything with any kind of foam. I can tough it out for another month, but once the warm weather hits, I'd like to tackle the situation.

I agree, I definitely need to do something with the rim joists, and I will take a look around the exterior, and make sure my two access panels are snug.

Perhaps I will focus on those items first and see if it makes a next difference next winter before I go through with the spray foam.
 
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