spray foam over radiant heating? | Ask Mason Knowles - SPF Consultant | Spray Foam Technical Questions and Answers | SprayFoam Magazine Q&A Forums

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Posted: Feb 27, 2009 09:00 PM	spray foam over radiant heating? can you spray foam (2 lb cc)over radiant heating pex tubing ? thanx snider
Eric Machemer Posted: Feb 28, 2009 12:22 PM	We had the same question a couple of months back. I would check with the manufacturer of the particular tubing, but the brand we were dealing with OK'd the use of open cell foam but not closed. The reason had to do with the exotherm temperature of the foam being processsed. It seems that there is an oxidized coating on the tubing that can be compromised if temps reach over 250 F. We decided to use open cell to be safe, but if we were to use closed cell we would use smaller lifts to minimize exotherm temp. That being said, I don't know how tubing manufacturer would handle warranty issues if they found closed cell on the defective tubing. I would strongly encourage contacting the tubing manufacture if I were you. I am sure they would be happy to give you an answer. If they OK it... have them send it in writing. Hope this helps.
Frank Bood Posted: Feb 28, 2009 01:54 PM	Is there a PEX that can go over 200*F?
mason Posted: Mar 02, 2009 07:15 AM	The Spray Polyurethane Foam Alliance has been conducting research on spraying over PVC tubing including pex. As you mentioned the tubing has very low temperature ratings and closed cell SPF typically develops temperatures in excess of 200 degrees F during the rise period. Until some definite data and recommendations have been generated by the industry, I would recommend that you spray a 1/2 inch of foam first over the tubing let it set them build up thickness. This will keep the higher temperatures from reaching the tubing. Other issues from a few of the tubing manufacturers relate to perceived chemical incombatablitlies with SPF, but we have observed no evidence of this.
Bryan Kwater Posted: Mar 02, 2009 08:43 AM	What about using foam pipe insulation from Home Depot on the pex first, then spray foam over that. The closed cell foam would not touch the pipe itself.
William Gibson Posted: Mar 02, 2009 11:20 AM	Put a reflective barrier (reflective bubble wrap works good) under the radiant system then spray to the reflective barrier. Make sure there is a 1-2" airspace between the pex and the reflective barrier. If you spray right to the pex tubing then how good can the radiant system radiate?
Bryan Kwater Posted: Mar 02, 2009 11:59 AM	I am assuming he is not looking to insulate the pex that is in the flooring, but rather the tubing that comes up into the wall.
Posted: Mar 02, 2009 08:23 PM	Newmam11 has it correct. Foam right over pex thats in between 1st fl.fl. joists. House is on pilings with tital water beneath it.
William Gibson Posted: Mar 03, 2009 06:46 AM	I wouldn't "foam right over it". You need to create an airspace between the insulation and the pex. While your at it why not put a reflective in front of the insulation so it can help bounce the heat towards the living space.
SPFer Posted: Mar 03, 2009 08:19 AM	You do not want to spray over the pex, the foam will wrap the pex and hinder it's heating capabilities. I would install the reflective bubble wrap mentioned by Newman11 if the foam is going to be covered. If it is not to be covered, I would install the rigid board with the reflective surface. The reason for this is to have a stable surface for the foam so it does not fall out of the cavity. I do not trust the bubble wrap as a solid spraying surface.

Author

Comments

Posted: Feb 27, 2009 09:00 PM

spray foam over radiant heating?

can you spray foam (2 lb cc)over radiant heating pex tubing ?
thanx snider

Eric Machemer

Posted: Feb 28, 2009 12:22 PM

We had the same question a couple of months back. I would check with the manufacturer of the particular tubing, but the brand we were dealing with OK'd the use of open cell foam but not closed. The reason had to do with the exotherm temperature of the foam being processsed. It seems that there is an oxidized coating on the tubing that can be compromised if temps reach over 250 F. We decided to use open cell to be safe, but if we were to use closed cell we would use smaller lifts to minimize exotherm temp. That being said, I don't know how tubing manufacturer would handle warranty issues if they found closed cell on the defective tubing.

I would strongly encourage contacting the tubing manufacture if I were you. I am sure they would be happy to give you an answer. If they OK it... have them send it in writing.

Hope this helps.

Frank Bood

Posted: Feb 28, 2009 01:54 PM

Is there a PEX that can go over 200*F?

mason

Posted: Mar 02, 2009 07:15 AM

The Spray Polyurethane Foam Alliance has been conducting research on spraying over PVC tubing including pex. As you mentioned the tubing has very low temperature ratings and closed cell SPF typically develops temperatures in excess of 200 degrees F during the rise period.

Until some definite data and recommendations have been generated by the industry, I would recommend that you spray a 1/2 inch of foam first over the tubing let it set them build up thickness. This will keep the higher temperatures from reaching the tubing.

Other issues from a few of the tubing manufacturers relate to perceived chemical incombatablitlies with SPF, but we have observed no evidence of this.

Bryan Kwater

Posted: Mar 02, 2009 08:43 AM

What about using foam pipe insulation from Home Depot on the pex first, then spray foam over that. The closed cell foam would not touch the pipe itself.

William Gibson

Posted: Mar 02, 2009 11:20 AM

Put a reflective barrier (reflective bubble wrap works good) under the radiant system then spray to the reflective barrier. Make sure there is a 1-2" airspace between the pex and the reflective barrier.

If you spray right to the pex tubing then how good can the radiant system radiate?

Bryan Kwater

Posted: Mar 02, 2009 11:59 AM

I am assuming he is not looking to insulate the pex that is in the flooring, but rather the tubing that comes up into the wall.

Posted: Mar 02, 2009 08:23 PM

Newmam11 has it correct. Foam right over pex thats in between 1st fl.fl. joists. House is on pilings with tital water beneath it.

William Gibson

Posted: Mar 03, 2009 06:46 AM

I wouldn't "foam right over it". You need to create an airspace between the insulation and the pex. While your at it why not put a reflective in front of the insulation so it can help bounce the heat towards the living space.

SPFer

Posted: Mar 03, 2009 08:19 AM

You do not want to spray over the pex, the foam will wrap the pex and hinder it's heating capabilities. I would install the reflective bubble wrap mentioned by Newman11 if the foam is going to be covered. If it is not to be covered, I would install the rigid board with the reflective surface. The reason for this is to have a stable surface for the foam so it does not fall out of the cavity. I do not trust the bubble wrap as a solid spraying surface.

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