Heated/unheated crawlspace?


Old 11-02-02, 08:05 PM
Mark B
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Heated/unheated crawlspace?

I've been reading up on insulating my crawlspace, as well as following these posts on the subject. Yet, I still haven't found a definitive answer to my situation: is my crawlspace considered heated or unheated? I've read that you want to insulate the walls of the crawlspace if it is heated, and insulate between the joists if it is not.

My crawlspace has a dirt floor, cement block sides and is ventilated at all four corners (it runs under the entire house). Also, the forced air gas furnace and all heating ducting is in the crawlspace (the ducting is not insulated). Is this considered an unheated crawlspace? The original owner had insulated the walls with R-19 fiberglass batting, but not between the joists. The house is a drafty ice box most of the winter. I've considered removing the old batting on the wall and instead insulating under the floor between the joists. However, my greatest concern is for the plumbing within the crawlspace. Will this lead to frozen pipes, even if I have them wrapped in foam insulation? Also, if I eventually insulate the heating ducts, will this cause more concern for the plumbing? Thanks.
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Old 11-02-02, 10:07 PM
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The vents in your crawl space are there to prevent moisture problems in the crawl space. This moisture is a direct result of heat because all heat has moisture in it and heat condenses against cooler objects. The vents provide air that can absorb both the heat and humidity which avoids moisture problems in the crawl space.

There are several sources of heat in your crawl space, such as the ceiling of the crawl space, heating system, duct work and pipes. The truth here is that you want the heat from all these sources inside your home and not in the crawl space. This describes your thermal boundary. In other words, the place or area where you want insulation applied in order to use the heat from these sources for the home. As the heat is emitted from these sources are reduced in the crawl space, you decrease the probability of moisture problems in the crawl space.

You should insulate the ceiling in the crawl space, insulate the ducts and pipes too. You should have a service person inspect the furnace concerning the insulation around the exchanger and in the compartment for the blower.

Plastic covering for the dirt floor prohibits ground moisture from entering the crawl space and evaporation, which takes heat to occur.

So it is not a question on whether the crawl space is heated or unheated. It is whether or not you want the heat you paid for used in the crawl space or the home?
Old 11-03-02, 08:48 AM
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crawl way

Im sorry but i dont buy this. I dont know how many of the insulated floors I have had to take out and redo. Some the ply wood subflooring was comeing apart.We started doing this back in 1965. A 4 or 6 mil poly on the ground over lap it about a foot. also run it up the walls about 12". Cut up a roll of R30 and put them in the joist space up on the sill plate all around the home.Now do the wall with a 2" or 3" insulboard or what you can get there and put it on the walls close all of the vent for sure.Now take and cut in 2 register out lets in the heat duct and one in the return.If you have a door to this crawlspace be sure and put insulation on it. No we dont use insulated duct here in the crawlways. I think you are up in CO. It get cold and and wet here in MO. also. ha ve done this with oil, lp gas, elec, heat pumps. ED
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