Do I need crawl space insulation?

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Old 01-26-02, 11:30 PM
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Question Do I need crawl space insulation?

I live in a 1 story house built over a crawl space. I live in Michigan, where we have alot of temperature changes. My questions are: Do I need insulation in the crawl space? If so how and where should this be installed? What R value do you recomend? The crawl space is about 3 high cement block walls with a cement floor. There are 2 small vents and 1 large opening built like an outdoor cellar opening-a cement pit covered by a wood plank top. The opening itself has a glass window-which we use in the winter, and a screen that we use in the summer. Is this opening set-up ok? Thanks
 
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Old 01-27-02, 06:05 PM
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The set up with the crawl space door is fine.

You should use R-19 with a vapor barrier. The vapor barrier should be between the house floor and the insulation. In other words, you install the insulation in the crawl space with the vapor barrier facing upwards. The way you hold the insulation in place is with joist hangers. They look like a straight metal bar about the size of a clothes hanger and at the ends it is sharp. Once you install the insulation, take a joist hanger and push it between the joist to hold the insulation every three feet. The joist hanger is a little bit longer than the distance between the joist and the sharp points at each end dis into the joist to hold the insulation in place.
 
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Old 01-28-02, 05:28 PM
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insulation

I previously asked about insulating my crawl space. I want to make sure I understand your answer and directions.
Can I buy R-19 insulation with a plastic vapor barrier? Or is the paper faced considered a vapor barrier? If I don't put a plastic vapor barrier under the insulation - toward the floor of the crawl space, what prevents the insulation from asorbing the moisture that gets into the crawl space? Thankyou
 
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Old 01-28-02, 06:12 PM
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Vapor barrier

You can cover the soil in the crawl space with at least 6 mil polypropylene (plastic) for a vapor diffusion retarder.

Go to www.doityourself.com/insulate to learn more about insulation. See the article on vapor diffusion retarder (barrier).
 
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Old 01-28-02, 08:33 PM
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All faced insulation regardless if it's foil or paper is a vapor barrier. If you look on the packaging, you will see a rating usually SP-15. This rates the performance of the vapor barrier. Putting plastic after the insulation is installed will create a moisture problem. You will trap the moisture inside the insulation.

I understand your concern about moisture in the crawl space. Cold air can hold less humidity than warm air. When two masses of air that have different temperatures and humidity levels meet, they have the tendancy to mix and become one temperature and humidity level. This is known as Equilibrium Relative Humidity (ErH%). This is what your vents in your crawl space does for you. By providing access of the low humidity cold air outside to the somewhat warmer and higher humid air inside the crawl space, the two masses of air will equalize. Since there is considerable more low humid cold outside than inside the crawl space, the moisture problem is eliminated. Your vents are actually there for the winter and not for the summer.
 
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Old 02-02-02, 06:59 AM
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Thanks for all the info on insulating the house floor. Now I have another question ! Should I wrap insulation around the furnace ducts in the crawl space? Would the expense of the insulation outway the savings in heat loss from the ducts?
 
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Old 02-02-02, 07:22 AM
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Insulating ductwork in crawl spaces is mandatory. You lose 2 to 3 times more heat through the ductwork than through the floor. And is probably the major cause for discomfort in the rooms above, much more so than the floor insulation. Insulating ductwork in unconditioned areas usually have a payback in considerably less than a year. Whereas the floor insulation will be 2 to 3 years.
 
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Old 02-04-02, 05:27 PM
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OK !! So now I know I need to insulate the duct work in the crawl space; but what do you suggest I use ? And is there any special instructions on doing it? Do I need to look for the R value on this insulation also? Thanks
 
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Old 02-04-02, 07:50 PM
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Duct insulation usually comes in a roll that is 1 inch thick and 18 inches wide. You wrap it around the ducts and tape the ends together. DO NOT BUY THAT STUFF WITH THE SELF ADHESIVE, it usually falls off after awhile. Wear a face mask and eye wear. There's usually a lot of dust on top of the ducts. I like doing the ends first and all the joints, they are usually the most difficult to do and if you have to make cuts to fit the duct, I'd rather do it in the middle of the duct than at one of the ends or joints. Relatively easy job, but a dirty one.
 
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Old 06-08-02, 04:53 PM
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Crawl space insulation

My house is a single story wood frame home built in 1950. I live on the far north coast of California. The house is redwood construction with the floor joists being 4X8" beams 4' OC and 2X8" T&G subfloor with 3/4" oak finish flooring. I have already installed a vapor barrier on the dirt but not sure if I need floor insulation. Even so given the construction how would I install it?

In addition to the unusual floor framing my exterior is redwood siding with 1/2" of what looks like sheet rock underneath it. Anyone ever see this before?

OT - how do you get rid of those RD special offer pop up windows?

bit
 
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