Aluminum foil roof?
 

Every year here in Arizona the temperatures soar in the summer time to around 120F. The heat is just as much from the sunlight as it is from the ambient heat in the air.

So here's my question:
if i were to roll out and staple down some shinny aluminum foil on my roof - the entire roof - then would that reflect heat out or would the foil only heat up after just a couple of hours and bake the house?

getting enough aluminum foil from the $1 store to do the whole roof would only cost me between $20 and $40.

(but it's probably piss off the neighbors because they'd get even more glare on their windows.)

It should take the radiant heat load off ;)

A more attractive method is to use something like a privacy screen that surrounds the house (not like a fence to keep people out - it would need to be relatively close to cast a shadow) or planting for shade. But, that doesn't handle the roof....

But you're not limited to foil - any opaque radiant barrier will work....

What happens when the foil starts ripping and blowing away in the wind? Foil isnt very strong. Maybe try some sheet metal?

Might as well just have an old tin roof.

Meh, that's just a practical concern :D:p

Planting for shade:
In this part of Arizona it takes a lot of time and money to get trees to a good height.
There's money for buying, time for planing, money and time to water enough to grow a good size tree in the desert.

Shade Screen:
A Shade screen wouldn't get the roof and the expense would be much higher than just simply buying aluminum foil and using my staple gun to shingle them on the roof.

what about the ''Oven Effect" though?

do'h - you're in AZ.... Planting isn't the greatest of options....

Oven effect.... Ovens work on radiant heat and natural convection... You'll be losing the natural convection (for the most part) but you'll be drastically reducing your radiant heat. If you have one...

Get a meat probe and stick it on your roof and cover it with some foil. Measure the instant temperature. As the roof has had time to get up to temp - that value will be how hot your roof gets without a cover.

Unfortunately, without going full scale (due to conduction), I don't think you'll be able to get a temperature with the foil covering your roof.

-----
The more traditional alternative is to install an attic fan with a thermostat. Blow out the air and try to keep the air temperature in your attic close to ambient. The one my parents installed in their home (South Florida) cost somewhere between $50-$75. slightly more than foil - but it won't blow away in a dust storm and is more aesthetically pleasing for you and your neighbors.

Even cheaper (maybe?) is foam roof channel stuff at your local mega home improvement place o.0 It installs the full length of the roof from base to top in the attic and creates a natural chimney effect - but you'll need a way to vent that heat near your roof's ridge...

Thanks for the input, guys.
I'll discuss these ideas with my wife when she gets home and - if we decide to try anything at all - then i'll let you know how the bill changes compared to last year.

Try the perforated reflective material designed to put in your attic. It reflects away most of the radiant heat that penetrates the roof, before that radiant heat comes through the upstairs ceiling and into the house.

A white or light-colored roof is also a good idea, as it reflects away lots of solar energy, not just in visible spectra but also ultraviolet and infared.

Best to keep the house from getting too hot in the first place, rather than spending dough to extract the unwanted heat.

bhazard -

In an ideal world (lots of money, no complaining neighbors) I would do that as a "second roof" so that there is an airspace serving as an insulation layer between the roof and the tin roof. This way the main roof would remain shaded and would not have any of the "hot tin roof" parts convecting heat to the house.

Better yet, with even more money, the tin roof would be solar panels generating at least enough electricity to power an AC unit. Shade and AC all in one!!!!

WaxyChicken, how windy does it get where you are?

CarloSW2

WaxyChicken -

I wouldn't want a tin roof in direct contact with the house. The metal will heat up and convect into the building. The good part would be that it would cool very fast at night and radiate to the "infinitely cold" night sky.

Assuming your roof is a "normal" shingle color, I would beg the wife for permission to paint the roof white with some kind of elastomeric paint (i.e. something like this : http://www.elastek.com/home.html). A white roof is the only way to go in the desert (aesthetics be damned).

CarloSW2

Windstorms only occur once or twice a year here. spending $1 to replace ripped or missing foil would be cheap and pay for itself - or so i'm considering.
our current roof is indeed a "normal shingle" pitched roof.

Attic ideas: nothing will work there. The attic space is so small that even the home inspector couldn't get into it when we bought the house. (with a pitch of about 15 - 20 degrees, and only 536 sq ft. there is of course not even enough room to crawl up there.) so this counts out alternate insulation techniques. if i'm correct then we only have blown insulation up there - i can't picture anything else. And i know already there is no way my wife would consent to a fan in the vents - that's just up the electric bill.

I'll look into the paint idea.
I'm also considering mirrors. (boy, that would be so evil to the neighbors! :D)

and Frank Lee - you've made more smart ass remarks in my posts than i can recall.
I just thought I'd point that out to you before you really begin to annoy me. I know that a civilized and intelligent individual such as yourself would be sure to prevent that from occurring.

What color are you shingles? light colored shingles stay cooler, and because they stay cooler they last longer, and keep your cooling bills lower, you can also get white roof paint, it's normally used for flat roofs, and would look mildly tacky on a pitched shingled roof, but it would last and not blow away, you would apply it most likely with a roller.
You can get solar powered attic fans, they are easier to install because you don't have to run a wire to them, they only come on when it's sunny out and they vent more then attic vents without fans, but the non fan vents are another option, simply making sure that your roof has enough vents at the ridge, and at the eves.
Also make sure that your attic does have insulation! I've seen some stupid stuff done in warmer states, lack of insulation is one of the biggest, a housing inspector might have just been looking for roof leaks.
I would NOT staple foil to your roof, the staples will destroy your shingles, creating 10,000's of tears in your shingles, and the foil will be gone in a week or two, if you really want to put tin foil on something put it on your cars roof, shinny side up, using contact adhesive, I did this with my glass sun roof and it helped keep the car much cooler, it's now painted silver.
Steel roof stay much cooler then asphalt, and the attics of houses with steel roofs tend to be cooler as well, although anything put in the sun will get warm, a glass of water will get warm, even hot if put in the sun, a steel roof will also last 100+ years if installed correctly, and it can be recycled and you will be paid for it, asphalt shingles need special disposal permits in most civilized states.

Here are some ideas, although many of them might not be practical. Hopefully they'll serve at least as a mental exercise for what is possible. :)

In order of most practical to least:

* Swamp Cooler
* Increased attic insulation
* Paint roof white
* Solar Chimney
* Earth Cooling Tubes
* Green Roof
* Roof Pond

Some of the neatest ways of keeping warm in the desert have been around for centuries, the windcatcher:

Windcatcher
http://upload.wikimedia.org/wikipedi...AnbarNain2.jpg

I get the feeling that houses could be designed better if you left a monkey alone in a room with a pen and paper. It's amazing some of the ridiculously poorly thought out buildings architects churn out around the nation.

"Oh, so you want a home in the mountains...how about a ranch style? Oh, the desert...how about a ranch style?"

- LostCause

I put a fan on my roof and it really doesn't do much for the electric bill. Maybe 50 cents a month at worst. But it makes a huge difference in the house temperature. I went from running the a/c a few hours a day to only running it when it gets really hot a couple of times a month. It doesn't get as hot here (WV) as you get though but I am sure it will help reduce your a/c load way more than the small amount of electric it uses.

I would also paint my roof white or chrome plate it if I lived in AZ :)

If the foil strips traps moisture below them you could end up rotting your roof. Maximizse the ventilation of the attic and if you redo the roofing get shingles that will dazzle the neighbors.

Yes, a radiant barrier would work, however, I would use aluminized polyester (space blanket) instead of foil. In my humble opinion, I would abandon the idea alltogether. To much work for something that will rip off in a short amount of time. (not to mention looking like crap):D

Instead...Insulate, Insulate, Insulate. Payback in all seasons.

You could also go with the radiant barrier idea in the attic by stapling alum. poly. to your rafters (assuming it is a stick built with enough room to work).

An attic fan as previously mentioned would do wonders. I am also going this route as soon at it warms up. They make solar powered ones, so no wiring, and feels good putting up pv.

Better yet, go to www.builditsolar.com This is one of the absolute best sites on the internet. I visit it just about daily and have implimented several projects listed there. Tons of info, ideas, DIY, FREE. >Check it out.

That is the coolest thing I have seen in a while! It always amazes me that humans have historically had such a level of ingenuity even when they can't properly describe the natural events happening...

I've always thought it would be cool to design my own house that is partially in a hill or mountain. Some areas waste so much simply by living above ground.

I totally agree, not to mention it looks like hell too. I think a low-polluting lifestyle includes low visual pollution...:D The mountain idea reminds me of Rod Rylander. While he may be living a more rustic lifestyle than you imagined, he offers good points on mountain-living. Or you could go to the other end of the spectrum and build a house like Bill Gates. :p

http://ourworld.compuserve.com/homep...P7140352-6.jpg

Personally, I wouldn't mind a half-submerged berm home...hobbit-like. Heavily modified earth-ship comes to mind, with an urban vegetable garden. Totally off the grid, totally sustainable, but still in suburbia/urbia would be awesome. 1/5 - 1/4 acre...but now it's just a mental exercise. Quite a bit different from the average dream of a mcmansion, I suppose. :)

- LostCause

I've liked the idea of a green roof ever since i saw it on "Extreme Home Makeover". I could save some money on the implementation by building my own roof units and save money on watering by sending my brown water up there.

but it would still be expensive to implement, which is why I'm considering a foil or mirror covering on the roof.

Today i went outside and measured the peek of the roof. From peek pitch to cealing it's only 18 inches. from the front of the house to the peek it is 138 inches.


________________|18 inches_________________
138 inches. . . . . .| . . 138 inches

i don't know how many degrees that is, but it's very low pitched.

Ok, so staples may tear the roof. but there's always adhesive. I'm afraid that adhesive would melt in the hot sun. out here I've used duct tape on my car. during the summer time that would only last a week or two before the glue melted off in the heat.

also, there is the possibility of finding reflective paint - but i expect that will be more expensive.

wind doesn't scare me. Just layer it like you do the shingles and keep it tight enough down so that the wind won't be able to get under it and lift it up.

The thought here isn't to block the sun from hitting the house, or to absorb the heat at a higher level, but instead to reflect the heat and sunlight it before it even hits the shingles.

And moisture shouldn't be a problem - it's a VERY dry heat out here. people get nosebleeds because of how dry the air is.

Wow, that Earthship thing is totally cool! Thanks for linking :thumbup:

because of the low hight of the peek of your roof (18") I still think you are going to be best off insulating your attic space, and even adding normal non powered roof vents, $50 later and you will have a well insulated, vented attic, keeping your ceiling cool, and adding resale value to your house, a white roof will also add resale value to a house in Arizona, because the shingles will last longer, and your cooling bills will be lower, white roof paint looks to be about $25 a gallon, and should cover 100-150 square feet of roof, last many years and it will never blow away.

I highly agree with everything said here. Insulation, vent fan, and white paint. I suppose it depends on purity of the color, but white paint should reflect nearly the equivalent of a mirrored surface. It's cheap, easy, durable, and less likely to piss off the neighbors...and less conspicuous. :)

Since it's so dry there, I think a swamp cooler could easily take care of all your A/C needs. Cheap to buy, run, and maintain. Not to mention, it'll help with the quality of life...especially the nose bleeds...:p

Thank you Ed Begley. :D

- LostCause

The "white paint" would be an white elastomeric coating. They use it on mobile home roofs (I known, I live in one). You can by that stuff anywhere. Not to expensive, and it's made for roofs.

EarthShip. Man was I totally into that for about a year. I read all of the books and loved the concept, but good luck getting it past p&z. (not to mention a LOT of work) However, despite not going for the earthship in the end, most of the concepts that are contained in the books can be modified and applied to your current situation. I have done this with my mobile home and as a result, I have an all electric mobile home that had a monthly power bill of no more that 40 dollars a month, even in winter. Another suggested read would be Morgage Free by Rob Roy. It is inspitational/informative and lead me down the path I am on now. (owning my own home +2 aces free and clear before i turn 30) Check it out.

LostCause -

Also, if you live near an airport, I could imagine the authorities getting upset with you.

CarloSW2

The sun packs a mean punch. We just don't know how to absorb it or deflect it altogether.

if you have eve troughs, a rain barrel, old cistern, or surplus tank, a small properly sized pump, a soaker hose or two along the peak. running 24/ 7 will cool the tank back down everynight. late fall thur early spring heat the house with it. it will save enough power costs to finance a solar cell, battery and eventually run for free. You will have to monitor the water quality and add bleach when necessay. i bet, i could build it for a couple hundred. the sound of trickling water in the desert, priceless.

WOW that's a shallow roof!

You want to search for 'radiant barrier' and 'building science' to find what you're looking for. They are normally installed in the attic and used with an attic fan.

I think foil would get torn up pretty quickly.

If water were plentiful you could setup a roof sprinkler. The sun heats up the water and evaporates it, cooling it.

Too bad you have almost a flat roof. Those solar powered vent fans really work very well, but it doesn't sound like you even have enough room for a gable-end fan.

Go with the roof paint. There are special ones designed for painting roofs to prevent heat absorbing in. Paint won't blow off or make holes in your shingles.

It is well worth the investment, you won't be sorry.

The solar roof vents I've installed had an adjustable mount so they could be put in a near flat roof, or if they were near the ridge they could almost work on the north side of the roof or on a roof with the ridge running north south and they work really well, limiting the number of holes you need to saw thru the roof.

Why not just put a tin roof on top of the shingles, well actually steel or aluminum these days.
Its done all time here, use 2x4 strapping to create some airspace between the shingles and put in a ridge vent all the way across. You might have to get a bit tricky with the stapping as usually its put in perpendicular to the grade which isn't ideal for venting. Unless you are 12 years old it will be the last time you even think about your roof.
Shingles are not enviro friendly at all so never having to replace them is good selling point to the wife.
Ian

If you live the SW USA , Texas, NM, AZ, purpose built reflective foil on the underside of the rafters will give you the most bang for the buck. I typical 100+ day can yield 160F in the attic. Properly installed foil is supposed to reduce attic temperature down to the ambient temperature. Insulation?? Once the foil is done, you may forget the insulation.

Foil on top of the roof? Three possible problems: neighbors, city codes, winds.

CB

aluminum roof
 

I'm going to weigh in on the side of light colored roofing,and perhaps a spray-on radiant barrier on the underside of the roof deck.With the low pitch it sounds like you couldn't access parts of the attic if you had to.Avoiding all the load you can will pay dividends.Whatever you can do to insulate and ventilate will also pay you back,even if you have to shove the material in with a broom stick.You may have watering restrictions to stretch the Salt River,and so your not likely to be planting Burr Oaks to shade the house.Artificial xero-scaping,adding any manmade shading devices to any exterior sun-exposed surfaces will, as others have mentioned, give you some immediate relief.And I also advocate the swamp-cooler over refrigerated air,so long as all the golf courses,agriculture,and swimming pools have so altered the climate that they'll no longer function.

I like the foil idea... it would spare you having to wear the foil directly on your head, which would look really silly.

http://i350.photobucket.com/albums/q...spa/foil-1.png

Im here because I was thinking about this today. I have done something similar but it was on a RV roof. When doing a major repair on the RV roof I accidentally purchased a product called Peel and Seal (reflective) I thought I was getting the white stuff but I was happy after thinking about it for a min. Note that the white stuff is exactly the same but painted white. This comes in rolls and has a tar backing. IMO I think its perfect for what you want to try and wont look that bad if you use a heat gun to help conform to your existing roof. AND.,. if you don't like it you can paint it white or any color you like and keep the reflective benefits.

I look at the heat problem the same way the people who make fire suits do. Less insulation needed if you reflect the heat away.

ABOUT THE ATTIC FANS These are a bad idea no matter what way you slice it. I myself figured this idea was good until researched it. Bottom line is: Negative pressure in you attic will draw inside a/c up and out. You just cant seal enough to make it worth it. It took a lot of research to make my mind up about this one but.... Google: "do power attic fans work" Answer NO

Don't give up on the foil idea its going to work!:thumbup:

It probably has already been mentioned, but making your roof white [raises] the albedo.

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.

Huh? White reflects more electromagnetic energy in the visible spectrum than any other color. How can making your roof white lower its albedo?

I know this is an old thread, but someone had revived it so instead of starting a new thread about basically the same thing, I just wanted to know whether anyone has installed radiant barrier to their roof and what kind of results you got. I'm getting ready to install a new metal roof on my home which will be installed on firring strips above the existing roof which will leave approximately a 1" dead air space between the existing roof and the new roof. Everything I've read on the internet says the dead air space is necessary to receive the benefits of the radiant barrier. I installed Prodex insulation to the interior walls and ceiling of my garage at the home I used to live in and could tell a noticeable difference in the temperture of the garage even without any a/c or heat, so what I'm looking for is opinions of how well it will work both winter and summer if placed on the exterior of the roof. The main reason I'm going to the exterior instead of the attic space is because I live in a modular home and have no access to the attic to place the radiant barrier directly above the living space. I'm interested in hearing from anyone who has used radiant barrier in their attic or especially in the application I am thinking about.

I have installed a radiant barrier on the underside of most of my roof. I stapled it to the bottom of the roof trusses. Since my roof has a rather shallow pitch of 3 in 12, which is typical for a lot of older Florida houses, I couldn't do this closer than about within 2 feet of the eaves, since that is where the roof trusses overlap the ceiling joists. Since my house is only 24 feet wide and has a hip roof, that leaves about 20 % of the roof with no radiant barrier.

Still, it probably reduces the attic temperatures during the hottest part of the summer by about 20 degrees F. It is noticeably cooler in the attic, but it's still hot up there. So additional insulation on top the ceilings is still needed.

Hi,

I mistyped, and I have now corrected myself. Higher albedo closer to 1 reflects more heat and light; while a lower albedo closer to 0 absorbs more heat and light.

Kinda like open ocean water has a lower albedo than snow and ice.