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What is your opinion of using LOW-E reflective insulation for slab insulation?

I'm starting a home in South Eastern Wa. State. It will have a daylight basement. I was going to use for slab insulation LOW-E Reflective Insulation. Has anyone used that material before and what is your opinion?

The material is !/4 " foam foil.

Asked by Dan Easton
Posted Jan 1, 2013 11:35 PM ET
Edited Jan 2, 2013 6:53 AM ET


6 Answers

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Is this some kind of rolled, bubble-foil material? Is it 1/4" thick?

Answered by David Meiland
Posted Jan 1, 2013 11:38 PM ET


i think if you search here you'll find your answer.

Answered by John Klingel
Posted Jan 2, 2013 3:24 AM ET


The straight answer is that it is a con. Worthless. Junk. All of it. The person selling it to you is a crook or a fool.

Answered by Keith Gustafson
Posted Jan 2, 2013 8:21 AM ET


Thin foil-faced products -- with or without bubble wrap -- have extremely low R-values (generally about R-1 or R-2). When used under a slab, such products are virtually worthless.

To insulate under your slab, use real insulation (EPS or XPS) with a total R-value of R-5 to R-20, depending on your climate zone.

More information here: Martin’s Useless Products List.

In that article, I wrote, "Distributors of foil-faced bubble wrap “insulation” have a rich history of exaggeration and fraud. A September 2003 exposé in Energy Design Update documented several wild exaggerations by manufacturers. Although foil-faced bubble wrap has an R-value of about 1 or perhaps 2, several manufacturers have falsely claimed R-values ranging from 5 to 10. In hopes of avoiding FTC enforcement action, the manufacturers, caught red-handed, sent EDU a comical cavalcade of apology letters. The bottom line: foil-faced bubble wrap costs just as much as — and in some cases much more than — 1-inch-thick rigid foam. As building scientist John Straube pointed out, “I might recommend it if it were half the price of R-5 rigid foam, but if it costs more than R-5 foam then you have to be crazy or stupid to use it.”"

Answered by Martin Holladay
Posted Jan 2, 2013 9:04 AM ET
Edited Jan 2, 2013 9:38 AM ET.


I'm using silvered bubble wrap [Reflectix] as window shades.
Works great, totally opaque, rolls up nicely. Might actually
function somewhat as a radiant barrier as there's air space
on either side of it, but at a quarter-inch thick or so I'd
never depend on it for any sort of conductive R-value.


Answered by Hobbit _
Posted Jan 2, 2013 4:55 PM ET


Martin and others have pointed out in threads with similar questioning that foil faced radiation reflection can only happen if facing some air space, which obviously is not the case under concrete floors .

Conductive is the solely transfer mode of energy from the ground through your slab,
and foam insulation is the key there.

depending on its local availability, type 2 or HD EPS foam ( white foam ) is probably the best/cheapest option in ur case.

Answered by Jin Kazama
Posted Jan 3, 2013 1:15 AM ET

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