Radiant Insulation

ed_19

Radiant Insulation

What kind of insulation have you guys had luck with for radiant staple up systems? Watts recommends a foil faced batt insulation, but I am having trouble locating that. We have used the bubble type, and the solid foam foil faced board in previous projects with no complaints. I am curious why Watts specifically recommends not using the bubble type. At this point my best idea is to use the bubble type for the foil and add regular batt insulation for the r-value needed. I would like some advise from people with practical experience, not just regurgitation form a book. This is important due to the fact that this is my house.
Thank you
Bill

Mark Eatherton1

Save the aluminum for something more important...

like making beer cans:-)

Unless you can guarantee that NO dust will ever foul the face of the insulation facing upwards, the spectral reflectivity factor of the aluminum will be lessened to the point that it just not worth the effort. Use craft paper instead and save the aluminum for making beer cans.

What IS important is making sure that the rim joists are well insulated, and that a consistent air gap is maintained between the face of the insulation and the subfloor/tube assembly. I had a customer once with staple up that flat plain wouldn't put out the heat, even at 180 degrees F. They even added baseboard above the floor to help augment it and it STILL wouldn't keep the space at a desireable temperature. We went in and found that the insulators had pushed the insulation up tight to the subfloor/tubing assembly. It also wasn't foil faced insulation. We went in and simply pulled the insulation down and maintained a 2" gap throughout and VIOLA, the floor started heating like a banchee. We ended up having to lower the water temps to around 150 degrees F to keep from over heating the room.

I'm not sure why the Chiles bros keep advocating aluminum faced insulation. It works GREAT in the laboratory, but when applied to the real world field application, it gets a nice coating of dust on it thereby killing the spectral reflectivity.

I hope you did your hoomework prior to using plateless RFH...

ME

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ed_19

I did quite a bit of research before the installation. I did use plates. I put them around the exterior walls and any room I plan to use tile. I was really thinking about onyx, but the lack of plates frightened me a bit, being in upstate NY and on top of a mountain. It seems like all of the manufacturers suggest some sort of foil-faced insulation. If this doesn’t work then why do they recommend it? I guess as long as the R-value is there and what you are saying about the dust is true then no one would ever know.
I also used spray foam around the entire exterior bad joists to close any gap and provide insulation. It is a ranch so it worked out very well, and I figured it would work a lot better than batt.

Unknown

They bought the hype and then didn't follow up on the research out there that ORNL did, apparently. The foil really isn't worth the effort in floor applications.

Also, you don't need an airspace if you are using plates, just to make sure you don't misread ME's post.

R value is king in heating systems. It really is that simple. There are no reflective shortcuts in floor systems, not in joists, and not in slabs.

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Mark Eatherton1

Thanks for the clarification Rob...

I didn't know he was using plates. As Rob said, if you're using plates, NO AIR GAP. If you're doing suspended or staple up without plates, USE AN AIR GAP.

ME

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Ted_9

Wait a sec guys, doesnt RTIs' Radiant trak specificly say to use a 2" air gap?

PATRIOT HEATING & COOLING, INC.

Unknown

If it does, it shouldn't. There is no benefit to an air gap in a conductive plate installation. You are not trying to heat the air in the joist like you are with suspended tube without plates.

Wirsbo's joist trak diagram... joist trak being RTI's radiant trak rebranded... does not show a 2" air gap, btw. it does show insulation solid to the subfloor with holes bored in it for the tubing to run in.

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