radiant barrier

[Darn Cat]

has anyone installed radiant barrier for attic insulation?

how is it performing? any issues or tips?

 

[SteveF]

has anyone installed radiant barrier for attic insulation?

how is it performing? any issues or tips?

I haven't installed one but after reading the stuff on radiant barriers on
the ORNL web site you probably won't want to either. Also search on FTC to
see the cease and desist orders on the companies that sell radiant barriers
for inflated performance claims.

Steve.

 

[Darn Cat]

after reading the stuff on radiant barriers on
the ORNL web site you probably won't want to either

if it's ornl.gov, there are so many documents, could you provide a direct link or two?

what specific issue was negative, ie. moisture retention, hyped performance, something
else?

 

[SteveF]

if it's ornl.gov, there are so many documents, could you provide a direct
link or two?

what specific issue was negative, ie. moisture retention, hyped
performance, something else?

http://www.ornl.gov/sci/roofs+walls/radiant/rb_01.html

I use Alltheweb and get a number of hits with "ORNL radiant barrier" and
"FTC radiant barrier" as search words.

Steve.

 

[Darn Cat]

http://www.ornl.gov/sci/roofs+walls/radiant/rb_01.html

what was the negative issue in the above link?
I read it with a view toward learning the reason why I don't want to install it.

 

[SteveF]

what was the negative issue in the above link?
I read it with a view toward learning the reason why I don't want to
install it.

That the radiant barriers are good a blocking radiant energy but that
radiant heat gain is only a small part of the heat movement that needs to be
handled. Increasing conventional insulation will accomplish more. Radiant
barriers are most effective in places where radiant heat gain is a major
factor, like Florida where, strangely enough, most of the radiant barrier
companies seem to do their testing.

Steve.

 

[daestrom]

what was the negative issue in the above link?
I read it with a view toward learning the reason why I don't want to
install it.

The only 'negative' that I see is that claims of saving 15% to 42% are
misleading. It can save up to 42% of the ceiling heat load on A/C. But the
ceiling heat load is <25% of the total A/C load, and the A/C load is not the
entire electric bill.

So if A/C accounts for 75% of your electric bill in the heat of the summer
months, an optimistic view would be that installing a radiant barrier will
save you 42% of 25% of 75% of your electric bill. That works out to just
under 8% of your electric bill.

Yes, radiant barriers work (when installed correctly). But some suppliers
have been accused of over-stating their performance by taking quotes from
NREL like, "Radiant barriers ... can save up to 42% of the heat load from
your attic." Sounds a lot better than it actually is (< 8%).

daestrom