Insulation under sad for radient flooring Heat

[johnems]

I have talked to three different installers of Radiant Flooring heat in a slab type insulation. All three have a different approach for the ground insulation under the slab:

1) Want to use triditional 2" bluboard
2) Wants to use a white fome with aluminum reflector in the center. The calm is that this will reflect heat upward into the slab.
3) Is a fome product that has black plastic on each side of it. the calme is the it is break between the ground and slab.

I just want to think about what is the best insulation system under the slab I can do. To me the pay back over time makes this an important issue.

Also I am being told the bubble type insulation is not that good.

Any help people can give would be appreciated. Thanks

 

[sneezer41]

bubble is useless

AFAIK, reflectors only work with an airspace, so.....


unfamiliar with the black plastic coated

blue foam seems to work

 

[Chris J]

Agree. A reflective surface only works if it is adjacent to an air space, so bubbles and foam with an aluminum layer don't work in this type of application. Panels with bonded poly for a vapor barrier will only work if you seal the joints between all the panels.

Much easier and better seal with separate poly layer and blue foam.

 

[ScaldedDog]

In the spirit of adding to, rather than hijacking, this thread: Do any of you have experience with Insul-Tarp? I'm leaning in that direction for mine, but would like more opinions.

Mark

 

[brad d]

Dow SM, any foil is smoke and mirrors to me.

 

[5wndwcpe]

2" rigid, 25 psi, period. Many claims have been made for bubble type, foil reflective type, laminated poly etc.etc. and all have their detractors. But no one has ever come up with a good argument against rigid foam. It just works.

 

[sneezer41]

Insultarp is a waste of money. Check out the radiant heating sites.

 

[ScaldedDog]

Insultarp is a waste of money. Check out the radiant heating sites.

I did, and it looks like you're right. Thanks!

Mark

 

[Kevin54]

A reflective surface only works if it is adjacent to an air space, so bubbles and foam with an aluminum layer don't work in this type of application.

A reflective surface (to me at least) would only work if there was some sort of light present. For example...an infared heater or say even a Kerosun heater. They give off heat, but also give off some type of light, so in essence you are trying to reproduce what you already have by reflecting it back. But if you have a black garden hose and run hot water thru it, stick a mirror behind it, would it reflect heat back. I don't think it would radiate, but instead maybe just warm the mirror slightly. But like with a kerosun, the flame produces light and with that light comes heat. You are reflecting the light back off of a reflective surface and with that comes a certain amount of heat. Just the same as the sun shining on a mirror, you can direct the mirror to heat something up. But when the sun goes down, even though the mirror might remain in the same spot and it is still warm out, you lost any heat from the mirror. So a reflective surface under a slab in total darkness would be a total waste. But what you want is to insulate to keep from losing the heat that is being produced. You want the heat to escape up but not down or out thru the sides.

 

[rburke65]

Compare the "R" ratings. The rest would fall under the catagory of opinion.

 

[sneezer41]

RE: light vs heat

heat can be considered infrared radiation. through air a reflective surface will reflect non visible wavelengths of light. A metal panel on 1 inch spacers behind a wood stove is a reflective barrier.

 

[Kevin54]

heat can be considered infrared radiation. through air a reflective surface will reflect non visible wavelengths of light. A metal panel on 1 inch spacers behind a wood stove is a reflective barrier.

Not arguing the point, just trying to understand. Would it be a reflective barrier, or would it actually just absorb the heat and then add to what is already being put out by the original source? I guess it would be interesting to see an experiment with a stove to see what the difference would be with say a mirror behind a woodburner and a black metal panel behind a woodburner to see the difference in heat output. Anyone got MythBusters phone number?

 

[comp]

hey thats a good one to send to Mythbusters