R-29 in 1" thickness?

[David Meiland]

I was in a designer's office yesterday and was shown a sample of an insulation product. It's basically 1" thick white foam board with foil on both sides. The foam itself resembles the type that is made into packaging... i.e. you buy a new computer and it comes in a box with corner pads made of foam... this foam looks like that, made of small balls or pellets all mashed together into a panel. Different material than XPS.

Anyway, he's been told that this material will achieve R-29. I asked whether he had been told to keep it spaced away from adjacent surfaces, or anything else, and the answer was no.

R-29 in one inch seems highly improbable to me. Can someone clear this up?

[Martin Holladay]

David,
Foil-covered expanded polystyrene -- that sounds like a product called P2000, although it may be an imitator jumping into the market with inflated R-value claims that are just as exaggerated as those of its famously inaccurate predecessor.
P2000 has lied repeatedly about its R-value, which is actually in the range of R-4 to R-5 per inch. Energy Design Update, in its June 2006 and August 2006 issues, has documented the company's exaggerations, and several provincial governments in Canada, and state governments in the US, have issued injunctions against the company, ruling that their advertising should reflect reality, and must not exceed R-5 per inch.
If you are able to find more information on the source of these exaggerations, post them for all of us to see. It's important to try to expose the fraudulant advertising of companies attempting to illegally take money from gullible architects, designers, and builders.

[David Meiland]

Thank you Martin. I suspected as much.

Can you fill us in on the foil face, what it does and doesn't do, and whether or not it needs to be spaced away from adjacent surfaces in order to be effective?

[Toolwhore]

David;

Here's a link for the Foil-Foam-Foil products I found awhile back:

www.insulation4less.com/tech_data_ffmf.asp

These are the manufacturers #'s. They sent me a nice sample pack, but we weren't convinced and never used it.

[Martin Holladay]

David,
The foil is a radiant barrier. Foil is a conductor, not an insulator, so it does not contribute to R-value. If a radiant barrier is installed adjacent to an air space, then the entire building assembly -- including the insulation and the air space -- will have an R-value greater than the insulation alone (although certainly not R-29); the R-value of the assembly will vary depending upon several factors. Radiant barriers are only effective if there is a significant difference in temperature between the surface and the adjacent air -- that is, if there is insufficient insulation. If the insulation is adequate to keep the surface close to the temperature of the air it is adjacent too, the radiant barrier doesn't do much. That's why they put radiant barriers in steel warehouses -- the buildings are uninsulated, so anything helps. If your wall or ceiling is adequately insulated, it doesn't need a radiant barrier.
Do a Google search on "radiant barriers" if you want to know more, but be wary of your source. Anyone selling radiant barriers is likely to exaggerate. You can trust the Florida Solar Energy Center (FSEC) Web site, as well as the Oak Ridge National Laboratory (ORNL) Web site.

[user843839]

Isn't readily available Thermax a foam with foil on both sides along the lines of this discussion or are you guys talking about some specialty product?

[Martin Holladay]

Tom,
To the best of my knowledge, Dow, the manufacturer of Thermax, is accurate in its R-value descriptions of the product and is not guilty of exaggeration. However, the manufacturer of P2000 is well known for exaggerating the R-value of its product.

[reinvent]

Here is the skinny from Dow it's self

http://www.dow.com/styrofoam/na/iso/thermax-ld.htm

[campster]

I don't mean to hijack this post but I have a question about Thermax.

Isn't readily available Thermax a foam with

I sealed my crwl space and was planning on using 3" Thermax to insulate the walls in the crawl space. I don't have much time for these projects so I wanted to buy a sheet or two each weekend until the project was complete. When I tried to find Thermax in Jacksonville Florida, no one knew what I was talking about. I finally called Dow to get a list of their distributors and found one in Jacksonville. I had to order a minimum of 15 sheets of the 3" boards at $80 per board. As I said, I don't have the time to install all of this at one time and I don't have the space to store the material either.

Is Thermax easier to get in other areas? Is the cost the same?

[reinvent]

Campster:
Why not store the insul in the crawl space until you are ready to install it. Take out what is in your way during each instal.

[campster]

I'd have to cut all the sheets down to 24 inch strips because the crawl space opening in pretty small. I'll have to cut them down anyway but I didn't want to chop up all 15 sheets and have them lay around for a year.


Does $80/sheet sound reasonable?

[Hausdok]

Don't know, call around to suppliers in your area and compare notes to find out. If there's only one, he might be paying more for it than the guy in a town where there are 20 and he's going to get whatever the market will bear.

OT - OF!!!

M.

[Mark Parlee]

Campster

Any reason you want to use the Thermax?

I buy 1" dow blue for $11/sht
2" for $21/sht

If you want three inches you could always buy some of each and lamineat them together with some styro-bond.

This equates to $32 for 3"s of foam, round numbers $50 less per sheet than using the Thermax

Is the Thermax any better for your specific application?

[campster]

I want Thermax because it's the only foam board product that I can find that does not require a thermal barrier. With Thermax, I can secure the boards directly to my crawlspace walls and not worry about an inspector questioning why it is not covered by sheetrock. If you look close to the blue stuff, it requires a thermal barrier.

Are there other products that can be used?

[Mark Parlee]

Why not use a spray foam insulation