# Do the radiant barriers work in the attic?



## imola ghost

I mean that it seems in theory it should/would work but does it actually help out any?

It it a DIY type install and the costs don't seem to be more than about $350 for about 3500sq ft of the foil. 

But does it actually produce any savings? Does it make the home feel more warm/cool?


----------



## operagost

It should work for the same reason an old-school glass thermos works, or a modern car sun shade. I'm planning on doing the same in my house. It's most effective at keeping heat out in the summer; unfortunately, I couldn't get it done in the spring to take advantage.

The two methods are to hang it from the rafters or to lay it on the floor of an unfinished attic. The former is best in a hotter zone. The latter is best in a cooler zone, but it also requires a little maintenance because over months or years you might build up some dust and it will become less effective. I would guess that when in doubt, the latter method is best in all but te hottest climates because it keeps your heat from ever entering the attic (where it's pretty much wasted the same as if it went out the roof)-- as long as you have good attic ventilation. If you don't have at least a ridge vent or turbine, an asphalt shingle roof might get too hot.


----------



## Gary in WA

Location, loc., loc.: http://www.ornl.gov/sci/roofs+walls/radiant/rb_02.html

Gary


----------



## operagost

Thanks for the informative link, GBR. I don't have central air, so I forgot about the attic duct issue. That's a big one! I do know that there are reflective insulating wraps for ducts, so one could still go for the floor and wrap the ducts for a little more expense.


----------



## Gary in WA

Compare the costs of a barrier to just more insulation: http://www.ornl.gov/sci/roofs+walls/radiant/index.html
Examine the hype: http://www.ecohomemagazine.com/ener...lose-look-at-common-energy-claims.aspx?page=5

Gary


----------



## Tedders

*Do radiant barriers "cook" the roofing shingles?*

Hi, y'all.

I'm considering putting radiant barriers on the underside of my roof (in the attic). Won't the reflected heat make the shingles so hot that the manufacturer's warranty be voided? Or, shorten the life of the asphalt shingles?

Thanks! 

Tedders


----------



## operagost

I have read a few studies on radiant barriers, and this was not a problem in any of them. The roof only gets a few degrees hotter.


----------



## BobbyParagon

*Keep radiant heat OUT in the Winter.*

I live in an area where we DO get 100 plus days in the Summer and some zero days in the Winter. 

I presume that the outdoor winter temperatures, angle of the sun for solar heating of the shingles and the interior reflection of interior attic heat [ what little there is] all tend to MINIMIZE the impact of winter heat loss if installed overhead on the rafters. 

My ceiling is well insulated and I actively exhaust the attic during the summer. So I think I'm going to go ahead and install it this Fall. Any comments???


----------



## TJ_in_IL

FWIW, I have used some paint additives before, on my house from HyTech Sales http://www.hytechsales.com/insulating_paint_additives.html 
I am in no way connected to them, except for a very satisfied customer. I found it made a HUGE difference in my house, which suffered from lack of insulation, and no easy way to add any. 
I started with a test batch, and painted the hallway ceiling in my ranch house. While I was in the attic in November running electrical wiring, I noticed above the bedrooms the plaster was warm when I moved back the insulation. I check over the hallway, and it was cool to the touch- a very noticable difference! So, I ended up painting the rest of the house.


----------



## BobbyParagon

*RE: Insulating coatings*

There's been a proliferation of insulating coatings in the DIY area. The ones that claim to reflect solar loads appear to work better than those that insulate from solar loads. If one googles or bings 'insulating coatings' you'll see quite a variety of coatings available, with claims all over the place. Many are linked to military applications related to stealth technology. 


It's kind of hard to argue with anecdotal evidence, but the numbers I've seen appear to favor the full spectrum reflective coatings over the microsphere types that seem to claim both insulating AND reflective qualities. And I'm sure you have to look at a cost/benefit comparison as well to make better sense of it all. 

I'd still like to read some stories on the success/failures of using these interior attic reflective materials that are stapled to rafters interiors, ceiling joist, etc.


----------



## BobbyParagon

Excellent information, Gary .....


----------



## TJ_in_IL

http://www.ecohomemagazine.com/news...ure-drop-in-attics-with-radiant-barriers.aspx


----------



## tom_matthews

I've installed the Enerflex radiant panels between the roof rafters in my workshop (and unconditioned 2-car sized outbuilding). The result during the summer was a vastly more comfortable interior space because the workshop didn't soak up near as much of the sun's heat.


----------



## algored2deth

Here is another opinion. A bit more general in nature...

http://www.greenbuildingadvisor.com/blogs/dept/musings/radiant-barriers-solution-search-problem


----------

