Insulation for UltraFin

Alan (California Radiant) Forbes

We have just completed an UltraFin installation and are ready for insulation. I've spoken to a few insulation contractors; many of them think that foil-faced insulation with the foil facing the UltraFin is the way to go, saying it will reflect the heat away from the crawlspace and towards the floor. My thoughts are that once you heat the air with the UltraFin, reflective foil being a metal will only absorb the heat, not reflect it. Paying extra for reflective foil insulation is a waste of money.

Your thoughts?

ChrisJ

My opinion is you can only reflect radiant heat, so it depends on what's radiating, if anything? Try to picture anything that will be glowing (infrared) because that's what you can reflect.

It's not going to do anything to help with air.

hot_rod

I think the reflective qualities disappear shortly after installing any reflective materials under a floor. I opened a ceiling not long after a staple up rubber system was installed with foil faced batts. The foil was so dusty it was hard to tell it was even foil faced?

This was a new home construction so a lot of sheetrock and other construction debris had made it's way down onto the batts.

In theory the UF sets up some convective current in the joist space, so any dust seems to be distributed in the space and onto the insulation.

I'd rather spend money on thicker batt than reflective.

Canucker

It may help for a short time (not likely) but what happens when it gets covered in dust under the sub floor? Won't work very well then. If it were me, I'd pack as much insulation into the cavity as possible without a radiant barrier. It's cheaper and you'll be farther ahead.

Terry O

For what it's worth here's a link to some interesting info on reflective foil products:
http://www.healthyheating.com/Page 55/Page_55_o_bldg_sys.htm#.WZHkK1X5hEZ

ChrisJ

I looked up what UltraFin is, that would help right?

In my opinion, a reflector would be beneficial. At the same time, the concerns about dust may also be true.

50/50?

Gordy

In a crawl space the Vapor retarding face of the insulation should be up away from the unconditioned space.

ChrisJ

Gordy said:

In a crawl space the Vapor retarding face of the insulation should be up away from the unconditioned space.

Depends on where you are and the conditions.
For example, in Florida, I would likely put it facing down.

Gordy

You don't want condensation trapped in the joist Bay Area. Which is what will happen if the vapor barrior is to the unconditioned space. If we are installing ultra fin we are most likely not in Florida. Even if we were in Florida vapor barrior to conditioned space.

ChrisJ

Gordy said:

You don't want condensation trapped in the joist Bay Area. Which is what will happen if the vapor barrior is to the unconditioned space. If we are installing ultra fin we are most likely not in Florida. Even if we were in Florida vapor barrior to conditioned space.

Incorrect.
Vapor retarder faces the warmer (typically) side. At least that's my understanding. It's kind of confusing, so who knows maybe I'm mistaken.

But as you said.
No one is installing this in Florida.

Gordy

It can be confusing. Then throw in the mix if this crawl space is vented, or not, and is the floor dirt, or concrete with a vapor barrier in its detail.

When walls are insulated with FG insulation batts with a vapor barrier. The barrier is always to the conditioned space. No matter what climate. However if we blow insulation in walls there is no vapor barrier, unless there is house wrap on the exterior which is breathable. Then there is spray foam....


Personally I have seen the foil vapor barrier to the bottom of the floor joists in crawl spaces, which is not correct with zero issues. However the floor was not heated. The crawl space was not vented only to the existing full basement which was conditioned. So the crawl space was semi conditioned.