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Radiant barriers seems to be a huge deal — Dallas is inundated with advertising about the energy and monetary savings that can be had if you just pony up the cash to install a radiant barrier. But what’s the big deal, and why haven’t my Toolmonger friends in the Midwest ever heard of it?

According to the U.S. Department of Energy, a radiant barrier is a highly reflective material designed to stop heat from passing from one open space into another. In other words, a radiant barrier is to heat radiation what a mirror is to visible light. This heat mirror can keep your attic cooler, or your house warmer.

Radiant barriers are less effective at keeping in winter heating energy than at keeping out the summer sun, and because they’re a whole-house solution, they’ll have the greatest impact if the whole house is cooled. Traditional insulation may still provide a better solution for keeping your house comfortable, but the radiant barrier is a good tool for the sunny South.

Photo of house-wrap application of radiant barrier posted on Flickr by Giles Douglas.

Radiant Barrier Fact Sheet [ORNL.gov] (Oak Ridge National Laboratory = U.S. Department of Energy)
Reflective Insulation [Energy Star]
Toolmonger Photo Pool [Flickr]


8 Responses to What’s A Radiant Barrier?

  1. pete J says:

    I installed a foam board insulation with a radiant barrier under the siding on my house. It was 1-1/2″ foam covered with a perforated foil. It was comparable in price as just the plain foam and it was easier to install so I bought it. My house is warmer in winter and cooler in summer now, but I would like to know if the foil really makes a measurable difference over just the foam.

  2. Rob says:

    I would like to know how it does in moist enviroments
    like the west coast does it compare to things like tyvek house wrap

  3. James says:

    I recently sold a 2000 sq/ft 2 story in the Austin area with no radiant barrier and my electricity bill ran about $380 per month with 1 AC unit. The house was bought new and 5 years old when I sold it

    I moved into a brand new built 1 story 3000 sq/ft home that has the radiant barrier and 2 AC units. Been here 3 years and the electricity bill is still $160 per month.

    The barrier does work.

  4. James says:

    The numbers I quoted are in the dead of summer.

  5. Ed says:

    Most of the advertising you hear is for the spray-on radiant barrier paint which at best will reflect about 75% of the heat. Unfortunately, there are some less than honest contractors who will dilute the paint with water since it is very expensive. Radiant Barrier Attic Foil will reflect 97% of the radiant heat and you can install it yourself with a staple gun and utility knife.

    Get a buddy and get it done! It’s a fairly inexpensive project that can have significant results.

    For complete info, pictures and instructions visit: http://www.AtticFoil.com

  6. phraust says:

    We used “Astrofoil-E” on a home we built last year, under a tile roof. After we had installed it, there was a significant drop in temperature. It went in easy enough (just staple it to the rafters, and metal-tape the overlap), and really wasn’t all that expensive.

  7. Toolboss says:

    The reason your Midwest friends haven’t heard of it is tat they don’t need it near as badly as y’all do in the South.

    We’ll average 70 or more days per year of below freezing weather, but only 10 days or so where the barrier against radiated heat (sunlight) is needed.

    On other words, it isn’t cost effective.

  8. Zathrus says:

    Most of the advertising you hear is for the spray-on radiant barrier paint which at best will reflect about 75% of the heat

    Which is about as effective as simply using some white paint.

    Spray on radiant barriers do not work. The Journal of Light Construction just had a bit about this (note: this link will NOT work after August 2008 unless you’re a subscriber: http://www.jlconline.com/cgi-bin/jlconline.storefront/EN/UserTemplate/82?c=890065e559a1af419c2202d7216b912a )

    Reputable organizations that don’t have an interest in your wallet (like southface.org and fsec.ucf.edu) do say that in warm weather climates (the US SE and SW) a properly installed radiant barrier can save you ~10% on your AC costs (not overall energy costs) during the summer.

    Note that FSEC also discusses their testing of radiant barrier paint and its utter uselessness.

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