crawl space insulating

Bill B.

I have a 16" to 18" crawl space under my floor. The space between the floor joists is not insulated. The ground under the structure is bare. I would like to know how I can winterize this space. What kind of vapor barrier to seal off the ground moisture? What's the best way to insulate the under side of the floor? The perimeter of the structure is sitting on concrete blocks and there is a small opening on each of the four sides for cross ventilation. After it's insulated, can I seal off these openings?

Unknown

I'm posting so I can see responses too, I have just this situation coming up for myself as well!

Lurker_2

Crawl Space

Fine Homebuilding had a very good article on this subject last year. You basically try to convert the crawl space to conditioned space and seal out moisture. You do this by covering the ground, first, with a good thick polyethylene plastic covering (or better yet Tu-Tuff Vapor Barrier) then a good heavy tarp (overlap and tape edges) that goes about 10 inches up the foundation wall. Then attach 2 inch thick blue board insulation to the foundation wall so that it covers the top of the tarp and seal all external air passages and external joist bays above the polystyrene with insulation (foam insulation is better). I've done this on my own house. I've had no moisture problems whatsoever. Just make sure any plumbing pipes are inside the conditioned space and not on the external wall.

Mike T., Swampeast MO

And a VERY good way at that.

Dirk Wright

Joseph Lstiburek: \"Builder's Guide\"...

In the book I have by him, "Builder's Guide to Mixed Climates" he states that crawl spaces should be sealed up and converted to "mini basements". If it was me, I'd excavate a few inches down, then pour a concrete floor (with plastic under the concrete of course), then insulate the walls and change the vent to a glass block window, add a small supply register, and insulate the floor. I'd also install a radon abatement system if radon is a problem in your area. Hope this helps.

Tom_35

Underfloor insulating

Wet-based cellulose can also be blown against the foundation wall if there is a contractor that is familiar with that function. Be sure to insulate the rim joists at the edge of the home as well.

Foundation vents are not recommended for ventilation anymore as well, although many building codes still have them in their codebooks.

The plastic sheathing and sidewall insulation are much better than the traditional method of batt insulation under the joists.

Tom Atchley
Ft. Smith, AR

Mike Thomas_2

JLC

Journal of Light Construction had a great article on this very topic, last year. You can get the article on line at JLC.com. Costs about 2 bucks to download, but a great step by step article. If you haven't subscribed to this great magazine yet, you are really missing out.

rob

Address?

I tried the JLC.com with no success. I'd like to visit website and possible subscribe. Is this the right www?
Thanks

hr

www.jlc-online.com

InsulTarp or The Barrier would be a good choice for the crawlspace. Put the white side up and it really brightens up the space.

it is a better R value than 6 mil, and a lot nicer to crawl on I also drapped my stem walls with InsulTarp. Foam blocks glued in around the rim joist, joist end, spaces.

I'm still hearing two versions of tightening up crawls. most agree, if it is dry, as it should be seal it up. if moisture is a problem it needs to ventilate. At least I think that is the latest.

Check the www.buildingscience.com website also.

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Mike T., Swampeast MO

Forgot to Mention

Make certain to check for brown rot (it's a fungus) while you're down there. You'll see tiny holes in the joists. If you find, such is a certain indication of high humidity. Strike joists with a hammer. You should hear a nice clear "ring". Wood infested with brown rot will have a thud. If severe you'll make a BIG dent. Slight cases probably won't require any sistering or replacement, but you MUST do something to reduce the humidity.

A heavy, very well sealed vapor barrier against the earth will do MUCH to lower the humidity. Sealing and insulating the perimeter is recommended because it eliminates the chance of condensation in joist bay insulation because you haven't used any joist bay insulation.

If you get liquid water in the crawlspace and cannot stop it, HotRod is likely correct that you're forced to ventilate. Don't even consider insulating the joist bays in this case! I've seen joists rot in less than 10 years in this area with a wet but ventilated crawlspace and fiberglass in the bays.

Lurker_2

vapor barrier

I've been following this thread since, I, too, am hoping to insulate my tiny crawlspace (18" or so) in the next few weeks.

It has a bare dirt floor and I was hoping to get someone to lay down a vapor barrier of some sort. What kind of contractors do I look for? Insulation specialists? Or are there other specialty trades I should look for to do this sort of thing?

Thanks,
-Michael

Patchogue Phil_29

Cleanspace Encapsulation

Do a google search on Cleanspace Encapsulation System.

Or go to basementsystems.com and request a local dealer.

RoosterBoy

Vapor barrier....

vapor barrier the ground and seal it withe tremco &or red tape...that is for Your health and comfort. like Mike said and Hot rod said you need someone to make a determination as to the moisture content and if there are any "Ventilation" openings other than the ones you think are there....it is still early in the year you could try some forced ventilation to get some of the moisture out on warm dry days..insulation is always a great way to go when the surfaces are dry,foam insulation doesnt stick to water.

mold and the like are a real concerne these days and because of the way some spores and crobes act on the human being i/d say that an erv might even be a pretty good answer...if you have an erv or hrv you can supply air to the space no problem,then, depending on the siding you might want to consider putting 2"foam board on the exterior of the crawlspace and up about 6" above grade ,to "finish" the foam you can have the local sheet metal company make some rather large Drip cap Z bar flashing type material it rises on the wall a few inches under the siding laps the insulation (by whatever thickness you chose and covers it down to the first few inches below grade,...if you want to do yourself a favor you can wrap the insulation with bitchuthane ...and mop the outside of the block with a waterproofing tarlike sealer then the foam then the trim then the siding...

from the inside you could have some foamer insulators come over when the crawl space is determined to be Dry and foam the box and rim joyst bays... and use some of the existing holes to place the erv supply and exhaust vents.the vents can be taken off from that space buh dont forget to make sure that they are taking air and exhausting air from 18" above grade *~/:)