Do radiant barrier felt products work?
jimAKAblue
| Posted in Energy, Heating & Insulation on
I had a roofer tell me that the radiant barrier substitute for felt will help with energy savings. Hiker and I were having a conversation and we both agree that it’s a waste of effort and dollars if there isn’t a space behind the radiant barrier.
Does anyone have evidence otherwise?
Replies
Titanium says that with their product being light colored, it transmits less heat.
That didn't make sense to me either.
Tu stultus es
Rebuilding my home in Cypress, CA
Also a CRX fanatic!
Look, just send me to my drawer. This whole talking-to-you thing is like double punishment.
it helps a lot until you put shingles over it
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where ...
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I think you have got it right. From what I've read a radiant barrier needs an air gap to work. I think it was U of FLA that had done a bunch of research and a web site that said as much. We had a thread on this maybe a year ago. Links were given in that thread.
A radiant or reflective surface can work ... but only w/ 2 things: the air space AND a clean reflective surface - which will not often happen in normal construction whether that space is enclosed or not. Over time and/or during construction, it will get dusty/dirty. So radiant systems work and test well ... in laboratory conditions. And while their benefits can be appreciated and the 'tests' speak for themselves, this isn't a 'real world' kind of approach.
Radiant surfaces that cost you nothing (e.g. foil faced polyiso) maybe give you some benefit and it doesn't cost much. But spending extra money on it? nah.
In my engineering heat transfer class, radiant barriers require an air gap to reflect the heat being transferred. Without the air gap and with the barrier in contact with the adjacent surface, the barrier is an effective conductor or heat, not a reflector. Any time a "reflector" dosn't have an air gap, all the hype is just that, hype.
Can't fool Mother Nature.
I think we have a consensus.
Possibly one of the FEW occasions on Breaktime.