Aluminum foil roof?

[Odin]

Originally Posted by Geonerd

Bare metal, be it aluminum foil, tin, or whatever, do not do well. While they do reflect a lot of heat, they also tend to be very poor radiators. The metal gets hot, and that heat works its way down into the house. Most of the 'cool roof' elastometric coatings are designed to be both highly reflective AND highly emisive. I live in Aridzona, in an old mobile home. The metal roof's original white paint had largely worn away, leaving bare, fairly bright, 'tin' in most places. Painting this with two thin layers of generic cool goop made a vast difference, reducing my summer cooling bill by ~50%. The roof itself is thin, without much insulation, so the 50% is probably a best-case situation. Now, if I can only do something about the poorly insulated walls...

Save the aluminum foil, it's too valuable as an anti-mind control device to waste on the roof! Get decent paint or cough the $ for light colored cool-roof tiles.

seems like you would be better just covering your roof with expanding foam or styrofoam sheeting

[Ford Man]

The foil was placed on the roof underneath the new metal roof a few weeks ago. I can already tell a difference in the house temperature. Although we haven't had a lot of really cold weather since installing it the house does maintain the heat better and we have already had highs in the low-mid 80's, but the warmest it's got in the house as far as I know is 77* and that was late in the afternoon after the sun had been shining on the house all day. I also put it on the ceiling of my garage, have insulated the walls with R-13 and started putting the barrier on the inside walls of it. I was in there today doing some work during the mid afternoon and was amazed how cool it was in there. It's a metal building and was actually cooler than the inside of the house and the house was only at 75*. This gives me even more reason to spend time in the garage instead of in the house with the wife.

[fidalgoman]

Originally Posted by sid

Both the Florida Solar Energy Center and the federal government have done tests and released the results on the net that show that white roofs save considerable energy in areas with high air conditioning requirements over any other color. These same studies show that white asphalt shingles, while performing better than other color shingles, still perform much worse than white metal or tile roofs.

Also, tests by the Florida Solar Energy Center show that properly installed radiant barriers on the underside of the roof do considerably reduce attic temperatures. But they still recommend at least R-19 insulation installed above the ceilings.

The Florida Solar Energy Center is funded by the state of Florida and may be a direct government organization.

This is right-on advice. Metallic (shiny) surfaces have been shown to be less effective than a highly reflective white. Also the purpose of an attic space is to separate the hot roof surface from the ceiling of the house. Insulation is used to further distance the heat source. One thing people overlook is just how hot your attic is getting. Way too little ventilation allows for a staggering amount of heat buildup that tends to creep into your home. Sometimes large slow moving fans are required to flush it out. Solar gain through walls and windows is another issue. One thing for sure, stapling aluminum foil to your roof will get you noticed, but perhaps not in the way you were thinking.

[Ford Man]

Thought I'd post an update on the radiant barrier. Our last electric bill was about $82. which I think is pretty good for a 1400 sf. home. We've been keeping the house at about 75* inside. I think the radiant barrier is well worth the money I spent. Where I was living in NC last year I was only cooling about 1000 sf. and the electric bill was running about $100.-$120. per month and the house wasn't as cool as where we are living now. I've also noticed that the a/c doesn't usually run for extended lengths of time. Since the 1st day of this month we have used about 400kwh and there have been a couple days where the heat index was between 110*-120*. I think our power bill for May when we didn't use the a/c at all was about $45. so the actual cost of cooling the house was less than $40. last month. I'd definitely recommend radiant barrier to anyone who's considering building a new home or just wants to make improvements to help on heating and cooling costs.

[j12piprius]

I finished stapling radiant barrier foil to the rafters a week ago and it's great. The garage used to get in the 90's and 130 under the rafters on 80 degree days. Today it was 90 out with bright sunshine, and the garage stayed under 78, very comfortable. The house was 77, and there is still a small more difficult section to complete.

The foil definitely helps, a lot.

I did it myself so it was quite inexpensive, a $10 stapler, and $65 each for three 500 square foot rolls.

[deathtrain]

I had to get a new roof after Ike came through Houston. I dont have an HOA so I had them put down the radiant barrier and install white r value shingles. I can tell you that it did make a change. the house is cooler and I seen average $100 savings in power during the summer.

[Ford Man]

Glad to see others trying it and having good results. My most expensive electric bill this summer was $112.xx and this has been an extremely hot summer for this area. The electric bills for June, July, and August were $82.xx, $112.xx, and $99.xx I'm cooling a 1400sf home with the radiant barrier cheaper than I was cooling a 1000sf house without it. I wish the walls of the house were also wrapped with radiant barrier and if I ever have to replace the siding on the house they will be.

[jakobnev]

I guess the next logical step is to aim all that sunlight somewhere it can be put to use, like block heater for your car, water heater, power generation... only your imagination sets the limits.

[j12piprius]

The climate is mild here so I never use a/c, even when it reached an all time record 112. I think the house (1367sf) got up to 83 that day, which wasn't bad, but I could feel the radiant heat.

My electricity use is 2.3 kwh per day ($6 month) and I only use gas for the hot water heater. I very much want to either convert the water heater to electric, or to build a solar water heater, depending on cost. The gas use is 3 therms a month ($6) mostly for the cost of generating the bill. The bills used to be a lot higher and so I did a lot of things to reduce them. Now I want to get rid of the gas bill, and keep working on getting rid of electric. I would love to be completely off the grid.

The gas bill used to be quite high from using gas heat in the winter.
I got a wood stove and haven't used the furnace for 8 years. I got rid of the gas range last winter.

The honda gets extremely hot though. I'm thinking of painting it white.

[foeller32]

A few years ago, I finished the attic in the house we lived in. The roof was only framed with 5" timber (old house), so I wanted to use 4" insulation, and leave a 1" air gap for circulation and to prevent mold growth. Almost on a whim, I bought a large roll of aluminum foil at Sam's Club ($20) and stapled it to the bottom of the plywood roof, shiny side out. Even before I insulated, I could tell a huge difference. I'm sure there are other products that would have performed better, but it definitely did work!

Though, I did lose out on all the free solar heat when the winter months rolled around.