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Author	Comments
paul rogers Posted: Sep 11, 2010 08:06 AM	hot water tubing mason, Customer has a crawl space he wants foamed. We have always foamed down the bond beam/wall and tied into 6 mil or thicker plastic.covering the dirt floor. Customer wants the thin board under the plastic tubing to be sprayed with foam. What is the best way to spray this crawl space?
mason Posted: Sep 11, 2010 03:03 PM	Is this radiant heating for the floor? Please provide some more detail on the construction. Is it wood floor, with radiant heating tubes running under the floor? Then a thin sheet of something, then the foam?
paul rogers Posted: Sep 11, 2010 06:49 PM	Mason, Wood floor/radiant heat tubes under floor/thin sheet of something. (customer is trying to figure out what material to put under the tubing) Then 2" of closed cell foam sprayed to the bottom side. (crawl space side)
mason Posted: Sep 12, 2010 10:04 AM	OK I got it. The foam would be sprayed over the thin sheathing and on top of the sheathing would be the tubes fastened to the underside of the flooring. Two concerns: 1. Will the foam stick well to the sheathing? Conduct an adhesion test on a small piece. 2. If the tubes spring a leak, the closed cell foam will trap the water. I am more concerned about this possibility. Those tubes are not real resistant to pressure and I can see this as a possibility that should be addressed. How have others addressed this situation?
paul rogers Posted: Sep 12, 2010 10:12 AM	Mason, Adhesion test is a good idea. Leaking? how often do these plastic lines leak? I have no experience with this type of heat. If we spray the crawl space walls, will the tubing warm up the crawl space just like the heating ducts? I am thinking we could accomplish the same efficiency with less foam and less cost to the customer.
John Shockney Posted: Sep 12, 2010 01:17 PM	Razerback The tubing used in radiant floor heating is unlikely to leak we put the same pex tubing in concrete. It will expand 3 times its diameter without bursting when frozen and return to its original size and shape after thawing out. The HVAC contractor installing the radiant floor should pressure leak check all the tubing before you insulate it and everything should be fine. The idea of just spraying the walls will not work in this system because the wood sub floor and floor coverings are insulators and if you don’t have more insulation below the tubing the heat will always travel in the path of least resistance heating the crawl space not the living space above. Of course you could heat the crawl space to 85deg plus to get the living space up to 70 but this would not be very efficient. You are correct that that you should cover or separate the tubing from the spray foam because if you spray directly onto the tubing or transfer plates the foam will wrap around the tubing and insulate it from the house defeating the way the system is to work. I have used house wrap or landscape fabric stapled in place as a separator and you should leave an air space between the tubing and the foam. Hope the helps Airpro HVAC Airpro Spray Foam
mason Posted: Sep 12, 2010 01:36 PM	Thanks for the first hand experience Airpro. Definitely make sure they pressure test the tubes. That would be my major concern of the application.
Daniel X Posted: Sep 12, 2010 03:16 PM	I don't understand how you expect to spray foam on the walls in the crawl space, over the tubing and then heat the crawl space...? Why would want to heat the crawl space?
paul rogers Posted: Sep 12, 2010 07:34 PM	dl123, Let me clarify. If we only spray the crawl space walls, would this provide enough heat for the house. (meaning it would also heat up the crawl space too) But airpro set me straight. just spray the thin board with foam from the underside. This is how I will approach this job when I meet with the customer. Without this forum, I would have sprayed the bond beam and wall down to the plastic. I Will suggest plastic on the floor anyway to slow/reduce the vapor drive. So airpro: 2" of CC to underside of board?
John Shockney Posted: Sep 12, 2010 10:44 PM	Razorback Yes 1-2 inches of closed cell will do the job, though I would also do the walls and rim joist also to keep pipes from freezing. Please keep in mind that you want an air space between the spray foam and the radiant tubing/ heat transfer plates. Thanks Airpro

Author

Comments

paul rogers

Posted: Sep 11, 2010 08:06 AM

hot water tubing

mason,
Customer has a crawl space he wants foamed.
We have always foamed down the bond beam/wall and tied into 6 mil or thicker plastic.covering the dirt floor.

Customer wants the thin board under the plastic tubing to be sprayed with foam.

What is the best way to spray this crawl space?

mason

Posted: Sep 11, 2010 03:03 PM

Is this radiant heating for the floor? Please provide some more detail on the construction.

Is it wood floor, with radiant heating tubes running under the floor? Then a thin sheet of something, then the foam?

paul rogers

Posted: Sep 11, 2010 06:49 PM

Mason,

Wood floor/radiant heat tubes under floor/thin sheet of something. (customer is trying to figure out what material to put under the tubing)

Then 2" of closed cell foam sprayed to the bottom side. (crawl space side)

mason

Posted: Sep 12, 2010 10:04 AM

OK I got it. The foam would be sprayed over the thin sheathing and on top of the sheathing would be the tubes fastened to the underside of the flooring.

Two concerns:
1. Will the foam stick well to the sheathing? Conduct an adhesion test on a small piece.
2. If the tubes spring a leak, the closed cell foam will trap the water. I am more concerned about this possibility. Those tubes are not real resistant to pressure and I can see this as a possibility that should be addressed.

How have others addressed this situation?

paul rogers

Posted: Sep 12, 2010 10:12 AM

Mason,

Adhesion test is a good idea. Leaking? how often do these plastic lines leak? I have no experience with this type of heat.

If we spray the crawl space walls, will the tubing
warm up the crawl space just like the heating ducts? I am thinking we could accomplish the same efficiency with less foam and less cost to the customer.

John Shockney

Posted: Sep 12, 2010 01:17 PM

Razerback

The tubing used in radiant floor heating is unlikely to leak we put the same pex tubing in concrete. It will expand 3 times its diameter without bursting when frozen and return to its original size and shape after thawing out.

The HVAC contractor installing the radiant floor should pressure leak check all the tubing before you insulate it and everything should be fine.

The idea of just spraying the walls will not work in this system because the wood sub floor and floor coverings are insulators and if you don’t have more insulation below the tubing the heat will always travel in the path of least resistance heating the crawl space not the living space above. Of course you could heat the crawl space to 85deg plus to get the living space up to 70 but this would not be very efficient.

You are correct that that you should cover or separate the tubing from the spray foam because if you spray directly onto the tubing or transfer plates the foam will wrap around the tubing and insulate it from the house defeating the way the system is to work.

I have used house wrap or landscape fabric stapled in place as a separator and you should leave an air space between the tubing and the foam.

Hope the helps

Airpro HVAC
Airpro Spray Foam

mason

Posted: Sep 12, 2010 01:36 PM

Thanks for the first hand experience Airpro. Definitely make sure they pressure test the tubes. That would be my major concern of the application.

Daniel X

Posted: Sep 12, 2010 03:16 PM

I don't understand how you expect to spray foam on the walls in the crawl space, over the tubing and then heat the crawl space...?

Why would want to heat the crawl space?

paul rogers

Posted: Sep 12, 2010 07:34 PM

dl123,

Let me clarify.
If we only spray the crawl space walls, would this provide enough heat for the house. (meaning it would also heat up the crawl space too)

But airpro set me straight. just spray the thin board with foam from the underside. This is how I will approach this job when I meet with the customer.

Without this forum, I would have sprayed the bond beam and wall down to the plastic. I Will suggest plastic on the floor anyway to slow/reduce the vapor drive.

So airpro: 2" of CC to underside of board?

John Shockney

Posted: Sep 12, 2010 10:44 PM

Razorback

Yes 1-2 inches of closed cell will do the job, though I would also do the walls and rim joist also to keep pipes from freezing.

Please keep in mind that you want an air space between the spray foam and the radiant tubing/ heat transfer plates.

Thanks
Airpro

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