# Spray foam insulation under floor in crawl space



## webbie (Feb 23, 2010)

Our vacation cottage has no insulation under the floor, which worries me...the utility bills are not too high, but the groundwater table is high and moisture will definitely eventually attack the underfloor plus it also rises up into the house through various wall cavities (plumbing holes, etc.)

I was thinking of possibly spraying 2" of foam under the floor - it has floor trusses and seems easy to get at. 

I noticed there are now some DIY kits for this, but not sure it would be worth doing myself. I go under there regularly, so that is no problem in itself.

Does anyone have any info on the DIY or on the general prices for getting it done by a pro? I had one friend mention that it would cost about $1. per square foot per inch of thickness....does that sound right?

Unfortunately, it is not my primary residence, so no tax credit would be forthcoming!


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## JustWood (Feb 24, 2010)

The $1 figure sounds about right.
If it's being sprayed against wood you need to use a certain type (open cell I think, it's been a while since I did mine) so it breathes and doesnt trap moisture. I think 1" will be plenty in an enclosed crawl space. You'll be impressed with the insulating capability of 1" of that stuff.


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## kartracer (Feb 24, 2010)

We used some on a cabin from a kit.If I remember right one inch is about equal to r7.I have no idea how much the kit cost,but it was easy to put on.It does expand and I think it is the closed cell you want for underneath.If you want I'll check with some the adjusters tomorrow to see what they're paying.I'm sure the would be a little difference in price in our 2 regions.


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## daveswoodhauler (Feb 24, 2010)

Probably don't want to go this route, but Flatbedford did a insulation job in his crawlspace and made some notes and pics here....might be more than you want to spend, but the product looks good.

https://www.hearth.com/econtent/index.php/forums/viewthread/51170/


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## webbie (Feb 24, 2010)

Wow, thanks...some good info.
I don't really need to put it on thick.....it's multi-purpose for moisture sealing, air sealing and some insulation. 2" would be more than enough....
But it might be a DIY situation where they charge homeowners so high for the material where it might be worthwhile to have a contractor come in because he gets the materials for less and makes the difference.


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## kartracer (Feb 24, 2010)

If I rember right,when he bought the kit,they ask how many board feet there was.It goeson fast.I'm like you,I wonder if a contractor could do it almost as cheap due to volume.It smells pretty stout when you're spraying it,at least this stuff did.We caulked everything that looked like it needed before putting it down.Don't know if it makes any difference or not.


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## JustWood (Feb 24, 2010)

If the perimeter of the cottage is skirted an inch should be enough.
I had my shop sprayed with 1.25" ceiling and walls.
At zero degrees outside temp I can back a truck in thats been on the road all day , shut the door and in the morning it will be 45-55 degrees (from engine heat) inside with no heat running through the night.
This stuff if applied properLEE will outperform fiberglass 2 to 1. I believe it's  the  perfect seal that makes it perform better.


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## bjkjoseph (Feb 24, 2010)

i just did it this fall,i used foam it green.....closed cell ,you can get it with an antimicrobial agent added...they had a deal on shipping.....this brand is good because when you have the right mixture,it comes out green and they have good how to videos on there web site.


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## G-rott (Feb 24, 2010)

Craig,

Check with foam contractors in the area.  With building business being slow you might be able to get a price a little lower than a dollar a board foot, for 2lb or hard foam.  Some manufacturers 1/2lb or soft foam is also rated as a vapor barrier at thicknesses of 3-4".  
Also vapor barrier paint can be sprayed on after the foam is installed, covering expose truss webs and other framing.

It helps too if prep work can be done before the contractor gets there, cover up mechanicals like pumps and get clutter removed.  

A good installer can do your job as cheaply as you can with DIY kits if there is one in the area.  
These spray rigs are a manufacturing facility on wheels, they control the mix rate, pressure and temperature, all the way to the tip of the gun.  
DIY products don't / can't control these factors.  So the results are more variable and depend on ambient air temp and moisture.

Do you have a vapor barrier on the floor of the crawlspace? That would be an inexpensive first step.  6 mill poly is a lot less expensive than foam if you dont need the insulation.  

Pm me if you have any other questions,

Garett


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## smokinj (Feb 24, 2010)

I  sprayed mine in for the same reason my well hits water at 8ft this isn't a easy job by no means on a diy that stuff is not forgiving and if you lift for more than a few sec.s you will need a new tip. I only done the out side block and rim board and filled the joist up 12in. off the foundation.I was into it about a 1000.00.


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## Flatbedford (Feb 24, 2010)

I was gonna tell you about what i did, but somebody already did that for me. The proper way to do it is to seal and insulate the crawl space and make it part of the house's conditioned space.


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## dvellone (Feb 28, 2010)

What Flatbedford and exactLEE says. 
Don't know the cold you experience while you're at the cottage, but I put r42 between my joists ( sealed the whole underside of the joists with 2" foil-faced polyisocyanurate + taped the seams) and until I put a skirt around the perimeter you'd of thought I had r-11 under there.

Using the poly might be a cost effective solution compared to having it sprayed though I don't know about its water resistance.


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## ChillyGator (Mar 1, 2010)

I  paid $1.30 sq ft installed 3.5" (R13 min) open cell foam

Open cell is not a vapor barrier, but down here it is the correct version to use.  I did not want anything to hold moisture against the floor joists or subfloor.  My house is old and on piers so I will install 6mill black plastic on the ground to act as a vapor barrier.  The house has been here since 1937 with no vapor barrier.


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## tom in maine (Mar 5, 2010)

DIY Spray foam is not going to give you as good a result as a contractor who knows what he is doing.
The cost of a dollar a square foot is about the same for the DIY product (of you are lucky) and contractor installed product.

Use closed cell foam only. Make sure you get someone who knows what they are doing! Check references.


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## PatMcNr (Mar 8, 2010)

I'd ask your insulation contractor about fire ratings and the fire code.

Its my understanding that spray foam is very toxic if it burns and must be covered with some type of fireproof or fire rated material.


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## swingline (Nov 1, 2010)

There are foam insulations that work extremely well that I've used throughout my house, but Foam It Green is NOT one of them especially for a DIYer, and I would not recommend their product.  After purchasing several canisters and having a 3rd arrive at a cost of close to $1000.00 for all 3, we had a faulty canister with no pressure that would not spray as promised while on a job site.  I spoke with their office while in the middle of an application and they INSISTED we take photos (which meant we'd have to stop work and close the site) so that I "prove" the product wasn't working.  As everyone knows, you cannot stop workers, run home, grab a camera, take pictures, drive BACK home, download photos, upload them to Foam it Green and then wait for their little judges to decide if it was their fault or mine.  They have refused to work with me on this or even SPLIT the difference in the cost of the product.  Instead their answer is to force me to buy ANOTHER canister and they'll give me 30% off the price.  I said thanks, but no thanks.  I'm not a moron.  If they don't stand behind their product and instead insist on treating customers with suspicion or criminals wanting to take from them - NO ONE should buy their product.  It clearly lacks reliability, and their company lacks professional integrity I’ve received from others I do business with, and when a faulty canister arrives, you're stuck with it along with a high price tag...unless of course you're willing to answer dozens of questions for 4 different people and send photos, weights of canisters, etc etc.!


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## vvvv (Nov 1, 2010)

board foam is cheaper but not as light [lol] tongue & groove also. spray foam adheres initially but wood swells & shrinx with humidity= how long will they dance?


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