insulation and radiant barrier

[weicm3]

The attic above my garage is not insulated at all. Will insulation in the attic help reduce the summer heat in the garage "A LOT"?? The two walls that are not adjacent to the house aren't insulated as well. I'm not planning to tear up the walls and insulate them.

Anyone uses radiant barrier? It looks like aluminum foil. Can I use it without putting the insulation in my attic?

 

[Shocker]

Yes it will make a difference. Alot

 

[red]

What about attic ventilation? A fan would help a lot. Personally I would insulate the ceiling with R-19 and install the radiant barrier on the rafters with a dual switch for the attic fan. Switch has the normal on/off for the auto thermostat and a second on/off for over riding the auto controls and being able to turn the fan on at anytime you need to work in the attic.

 

[weicm3]

What about attic ventilation? A fan would help a lot. Personally I would insulate the ceiling with R-19 and install the radiant barrier on the rafters with a dual switch for the attic fan. Switch has the normal on/off for the auto thermostat and a second on/off for over riding the auto controls and being able to turn the fan on at anytime you need to work in the attic.

Thanks. I have soffit vents and gable vent. It shouldn't be hard to install a fan there. Do you have dual switch wiring diagram that you mentioned handy? What thermostat switch do you recommend? I found this on amazon.

As for radiant barrier, should I just get it from HD? Anyone knows where I can get it cheap?

 

[SpudMaker]

I installed radiant barrier foil insulation from AtticFoil.com a couple of years ago. It has worked really well, is easy to install and tear proof.

 

[seabass]

I have the ATTIC FOIL the Spud mentioned and it has been awesome so far...

 

[Heath568]

I have a metal pole barn in KS that I installed the radiant barrier also. Wished I had done it when I originally built it.

http://www.radiantbarrier.com/index.htm

Had the attic foil guys beat by the shipping price when I bought. I think it all very similar.

I have been running some wires up in the attic this summer. Just finishing the last few wire runs, and I cant believe how cool it is compared to before.

 

[nonhog]

It seems most is perforated. I have a roll of non perforated. Any concerns ?

 

[Dolfan]

I have also been considering the radiant barrier products, but one issue I have is part of my attic is extremely tall inside, about 18-24'. Can I still get some gains by covering the areas that I can get to in a reasonable manner?

 

[rwhite692]

Yes it will make a difference. Alot

What Shocker said.

 

[Racer_X]

I had some leftover Reflectix foil+bubble radiant barrier from some experimenting I've been doing. Yesterday I stapled some up to the roof and took some readings this morning when the sun was directly facing that portion of the roof.

Outside: 81 degrees
Inside: 82 degrees
Bare metal: 108 degrees
Radiant Barrier: 91 degrees

Now I'm curious about the Attic Foil product. I bet it would be a lot easier to hang than the foil+bubble stuff.
I'm also curious about the perforations to let moisture through. I'm not sure if I need that or not.

 

[Racer_X]

I have also been considering the radiant barrier products, but one issue I have is part of my attic is extremely tall inside, about 18-24'. Can I still get some gains by covering the areas that I can get to in a reasonable manner?

This method may work well for you:

http://www.atticfoil.com/flat-top-instruction.htm

 

[Racer_X]

Bare metal: 108 degrees
Radiant Barrier: 91 degrees

I took another reading at high noon:
Bare metal: 120 degrees
Radiant barrier: 96 degrees

So far it looks like it makes a 14-17 degree difference at roof level even without any insulation or ventilation.

 

[SpudMaker]

Man, compared to my attic this is a breeze. Just staple the attic foil to one end, push it through the trusses and have someone else pull it tight on the other end. Staple and trim and your done. It will hang a little between the trusses (looks like about 10 ft) but will work fine and not much stapling. This should go pretty quick. Just leave a space at the top/bottom for ventilation.

 

[Dolfan]

I took another reading at high noon:
Bare metal: 120 degrees
Radiant barrier: 96 degrees

So far it looks like it makes a 14-17 degree difference at roof level even without any insulation or ventilation.

Your number look pretty good. eve a 10 degree drop in the attic should translate to a good savings.

Your also right the flat top method would help me in several places.

 

[GarageEnvy]

These readings are similar to what I've scene. I was at a home with two identical sheds in the backyard. One had radiant barrier roof sheathing and the other didn't. The owner was a mechanic and did it as an experiment before roofing his house. On a 90 degree day there was a 17 degree difference between the sheds. It was enough to convince me to use the sheathing when I re-roofed last month. This week is 100+ and I don't have any readings but I do know that my air conditioner is working less than in the past. I don't have any experience with the foil other than seeing one garage with it and the owner sweared by it. It was an old garage with no insulation.

 

[Car54]

What does this do to the shingle material? Does it concentrate more heat and wear them out faster? My roof had inadequate venting and it was literally popping the nails out.

 

[csp]

Both the AtticFoil and Radiant Barrier links mention that the difference to the shingle temperature is negligable. Of course they are probably using data from properly ventilated roofs and install the material so that the ventilation is not disturbed.

 

[Car54]

But it kind of blocks the soffitt venting, no?

 

[Racer_X]

But it kind of blocks the soffitt venting, no?

No, it doesn't block them at all. This instruction page may give you a better idea of how it is installed:

http://www.atticfoil.com/radiant-barrier-instruction.htm

 

[Racer_X]

The Attic Foil folks sent me a sample of their product. It was too small to put under the roof of the barn, so I taped it to a picture window, along with a piece of the Reflectix double bubble product.

Here are the temperature readings from my test:
Glass window: 108 degrees
Attic Foil: 90 degrees
Reflectix: 81 degrees

So, it appears that Attic Foil works very well, but Reflectix works even better. If maximum temperature drop is your primary goal, that looks like the product to buy. Some other things to consider are:

Reflectix is about 2.5 times more expensive. Attic Foil is 13 cents per square foot and Reflectix is 35 cents per square foot. I only looked at Lowe's and Home Depot - it may be cheaper elsewhere.

Attic Foil is lighter, at 28 pounds per 1000 square feet. Depending on whose website I looked at, Reflectix is somewhere between 55 and 70 pounds per 1000 square feet. I only mention this because if you are hanging it by yourself, the extra weight may make it more difficult to handle.

 

[randydupree]

Paint the roof with Lanco Urathanizer ,i painted the roof of my 8000sf building and the temp diff is incredible.
I didnt have a temp gun,but i did spray half of a sheet of roofing tim with it,leaving the other half un-painted.
The un-painted half was to hot to touch and the painted section was cool,i was feeling the bottom of the tin.
On the house the roof is tin,with a 1 1/2'' airgap,then 3/4'' pine tougue and groove,the pine wood was too hot to touch,after painting the tin,the ceiling was cool to the touch.

 

[Goobzilla]

Right now I'm in the research/planning/cost estimating phase of insulating my 40x64x12 pole barn. Looking at Prodex, Reflectix, and the Temp Shield product from Innovative Insulation. Any others I should consider? I've asked for samples of the Prodex and the Temp Shield. Looks like I'll need about 5000 sq ft if my calculations are correct. If I had to do this project in 2 parts which hopefully I won't, I would think doing the roof would be the best bang for the buck right off.