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Question DetailsAsked on 1/3/2015

how much should it cost to insulate a crawl space

I have an older home (built in 1935) that has no insulation in the crawl space. Vapor barrier just replaced. The house is a two story 1800 sq. ft. house.

I understand from another post that unfaced is the best insulation to use. Just wondering what price range I should be looking at, as I have two strikes against me: 1. I am not knowledgeable; 2. I am a female.

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2 Answers


You can find a number of prior similar questions with hints and ballpark cost info in the Home > Insulation and Home > Basement Waterproofing links in Browse Projects, at lower left.

Unfortunately, unless your vapor barrier (assuming on-ground type) is either a VERY heavy one (say 30 mil or more) or has a protective sand or insulation covering over it, it is likely to have to be peeled back to do the insulation or a protective layer placed on it, because the workmen putting in insulation in the flooring joist bays (assuming a ventilated crawlspace) will otherwise tear it up crawling around on it, destroying the vapor control you just put in.

If an under-joist vapor barriear, then it will have to be removed to place the insulation between the joists. Unfortunately, the vapor barrier is the last thing that should be installed - I am surprised the installer did not tell you that and try to upsell you on insulation at the same time.

For more info on crawlspace insulation fundamentals, you can go to manufacturer websites or websitaes like Inspectapedia, Home time, This Old House, and numerous Youtube videos to see the basics, and to learn about the essentials of moisure control.

Answered 5 years ago by LCD


Presuming that the thumbs down came from the original poster, sorry I did not give you what you were looking for in an answer.

I imagine the thumbs down was for lack of a typical cost - the reason I did not give a cost range was because there are a number of ways of insulating crawlspaces, depending on house construction and whether the crawlspace is being left open to outside air ventilation or being converted to conditioned air space. Also, moisture control is critical - donw wrong, it traps moisture and causes rot in the framing.

For a ballpark number for an outside-air ventilted crawlspace with full vapor barrier on the ground and no water infiltration issues through the foundation wall: assuming there is about three feet or more of crawlspace headroom to work in, just putting in batt insulation in the exposed floor joists and covering it with a housewrap product (to keep it from becoming a bug and rodent haven) can typically run from about $1+ to around $1.50/SF, depending on insulation thickness used and on whether the pipes are being foam-wrapped at the same time. For foam-in-place insulation - which can be a pain in the future if pipe or electrical repair is needed, and may not be suitable depending on what type of wiring you have (many types cannot be foam encapsulated), can run into the $2-3/SF range as a ballpark number.

Answered 5 years ago by LCD

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