insulate a crawlspace

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Old 12-20-03, 05:22 AM
101lineman
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insulate a crawlspace

I have a 12x14 extension off of my kitchen.This is over a 2.5 foot crawl space.The previous owners put regular bat insulation in between the floor joists.My problen is the floor is allways cold.Is there a method I could use to insulate the crawlspace/floor.I live in new york and in gets cold.I use oil to heat my house and presently have baseboard in the room.Could radiant tubing be a solution?Any advice would be nice. Thanks
 
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Old 12-20-03, 07:45 AM
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Lot of folks with similar situation here in the midwest will put a row of straw or hay bales all around the outside perimeter of the addition in the winter.

A layer of house wrap, like Tyvek, stapled to the underside of the floor joists might also help considerably.

There are a variety of floor heating solutions, particularly if your floor would hold a tile installation, Nu-Heat, & Warmly Yours are a couple that come immediately to mind.

If you had access easily to either nat gas or propane, there are ventless gas heaters that are becoming very popular also in this area for that sort of situation.

There's a few ideas, hope it helps. Happy holidays.
 
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Old 12-22-03, 06:02 AM
jmiddleton
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Fiberglass batt insulation doesn't work if it is exposed to the wind. You have to cover it with an air barrier. Tyvek is a good choice - make sure you tuck-tape the seams and tape over the holes made by the fasteners you used to install the Tyvek. Also be sure to completely seal the edges. If any air can get in, you're wasting your time. Another product that may be a bit easier to work with in the crawl space is Levelwall by Mitten. This product consists of sheets of thin styrofoam covered with foil and connected in a fan-fold. Like the Tyvek, you must tape all seams and edges to make an air-tight seal. One advantage of this product is that it adds a bit of insulation under the joists to create a thermal break.

Make sure that whatever product you use is permeable so any moisture that passes through the floor can escape.

Last, but not least, your choice of floor covering will make a big difference. Carpet is the warmest, tile the coldest.

Good luck.
 
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Old 12-22-03, 01:15 PM
101lineman
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Thanks for the info.The tyvex seems the way to go.
The kitchen floor is all ceramic so it conducts the cold real good.If I can keep the cold from comming up Ill stand half a chance. thanks again
 
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Old 12-30-03, 09:29 AM
A
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I have the same situation as 101lineman. We just extended the kitchen 10' x 24' and this new part sits above an open area 2.5 feet off the ground (where a deck used to be to help you picture it). It is effectively a crawl space that I have closed off on two adjacent sides with 1/2" durock cement board; a third side (one of the long sides) is of course the foundation of the origial house, and the fourth side (10' wide) is still open, but I plan to put up lattice (the basement dryer vent comes up into this crawlspace so I can't completely seal it).

So far I have placed R-19 kraft-faced insulation in the joists, with the paper side facing up towards the plywood of the floor. The fiberglas part of the insulation is exposed (which I have now realized based on the replies above is not a good thing).

Thus, I wanted to augment my current insulation by installing some type of board on the underside of the insulation: a) I'd like to increase the R-value just for the heck of it and b) I guess I need to provide a wind barrier for the fiberglas.

The 1-inch thick pink rigid foam boards sold in sheets of 4'x8' seem easy enough to install against the joists. I could even go cheaper and get the more flimsy styrofoam boards (lower R-value), or perhaps go with those boards with the balck shiny film (I don't know what those are).

Any recommendations? Also, any concerns of unwanted moisture buildup? Whatever board I use would be nailed/screwed directly to the joists and essentially come into contact with the fiberglas as the fibergalas is just about even with the bottom of the joists.

Thanks!

PS...I'm in Massachusetts.
 
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Old 12-30-03, 10:24 AM
MusicField
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You don't want to use any foam board that has a vapor barrier on it. You can use the pink foam board (extruded polystyrene), which is a vapor retarder, but not a vapor barrier. I'd go with the two inch thick stuff. It is tounge and grooved so it fits together nicely. Attached to the underside of the floor joists with the proper length screws/nails, it should do a nice job at helping to warm up the floor, as it eliminates the short circuiting (like a bridging effect) caused by the undersides of the floor joists being exposed to the cold.

Under floor radiant heat is the cadilac; if you do it, make sure you do it right.
 
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Old 12-30-03, 11:19 AM
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Lightbulb Open crawl

Azzurri Id for sure vent that drier on out from under there . Also cut vents in the other walls and let the other end open like you said Id put down a 6 mil poly on the ground there also.

Like Musicfield said you dont want any V/B on this other insulation board you put up there on the joist. Just think of this floor here as an outside wall of the home. let all the air get under this as you can. ED
 
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Old 12-31-03, 12:11 PM
jmiddleton
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Azzurri:

As mentioned above, LevelWall is designed for this application. It's fairly thin 3/8" or so but it is permeable and it covers the joists so, in addition to improving the effectiveness you your insulation by stopping convective loss you get some insulation over the 20% of your floor that has none right now. You should be able to get this stuff, or a competitor, anywhere that sells vinyl siding.

Adding an inch or two of foam would be even better but you need to make sure you have a good vapor barrier on the inside because this stuff isn't permeable and you will still need to cover it with tyvek to keep the wind out. You didn't say what floor covering you chose - ceramic tile will be cold no matter how thick the insulation is unless you have a heated space (or infloor radiant heat) underneath it.
 
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Old 01-01-04, 09:22 PM
A
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Great info, guys.

Based on your feedback, I looked up the Levelwall product on the web. If I can find it at a store this weekend, I think I'll likely go that route. If not, I'll use a layer of extruded polystrene covered by Tyvex.

By the way, I was mistaken about the dryer vent...the vent is actually from a basemet bathroom heat fan/vent that is hardly ever used so I think I'll be okay with letting it remain as is. As my kids get older, if they do start using the basement bathroom more regualrly, then I can always extend the vent duct to the edge of the crawlspace and thus to the true outside. Still, while I'm no expert, I would think that a bathroom fan is a far cry from a dryer and I'm probably good as is.
 
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Old 01-02-04, 02:48 AM
jmiddleton
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I've seen pictures of what can happen if bathroom fans are vented into an attic - it isn't pretty unless you like the look of rot and mold. I recommend that you buy a few lengths of ducting and a roll of duct tape and dump the vented air all the way outdoors. You should be able to solve the problem properly for $20.00 and a couple of hours effort.
 
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Old 01-03-04, 01:14 PM
bwlcardinal62
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insulating a crawlspace - ideas?

Along these lines, I'm looking to insulate my crawlspace which is 61' x 32' and help myself with energy costs. What impact might putting a layer of the pink stuff between the floor joists have? From a cost and heat perspective. I've priced it to be roughly $500 to do. Any thoughts?
 
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Old 01-03-04, 07:07 PM
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Lightbulb Dont do it

Go to the gov web it will tell you dont try and insulate the floor over a crawlway. Put a 6 mil poly down on the ground insulate the walls . and in the joist space up there on the sill plate all around the home
 
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