[WisJim]

The color of your roof can make a noticable difference in energy use in a home. A black roof (or other dark color) is generally the poorest choice. A dark roof is hotter in the summer, heating the attic and the rest of the house, adding to air conditioning or cooling cost. In cold climates, the snow melts off a dark roof before melting off a light colored roof, and you then lose the insulating value of the snow cover.

I wonder how much energy could be save world-wide if dark roofs were prohibited in most areas? One study claims $10 billion dollars energy and equippment savings in the USA. A no-cost method of saving lots of energy, and reducing equipment costs.

A few sites I found that touch on the subject:
http://www.consumerenergycenter.org/coolroof/
http://www.lbl.gov/Science-Articles/Arc ... color.html
http://www.ornl.gov/sci/eere/PDFs/sci_t ... 4p9_10.pdf
http://www.colormatters.com/energymatters.html

[thuja]

Like all new construction in the decades ahead, roofs will go through changes as well. Because we use petroleum based shingles right now- we will more than likely phase these out except for the very wealthy. What will we use?

Metal roofs are a good alternative but they will also be expensive as it is energy intensive to mine and manufacture metal products. We may move to wood shingling and perhaps thatch in some areas. It may take 50 years before roofs change completely and in that time we'll start seeing a lot of old and badly weathered roofs. My guess is that houses will start to fall apart due to poor roofs and the lack of money to replace them.

Lighter colored roofs are a good idea and there may be a shift towards lighter colored asphault shingles while we still have time (a decade?) but then we will be forced towards more traditional choices not based on fossil fuels.

[emersonbiggins]

Light-colored roofs and homeowners' associations are typically at odds with one another, especially in the south.

Too bad.

[willjones4]

not to mention the expense and resources used (from raw materials to supply chain) to reroof all those houses...

[Pops]

It is actually kind of hard to find extremely light colored shingles, I couldn’t get as light as I wanted.

Another case of detachment from reality, how many people that make the decision even consider radiated heat?

I don’t know how great the return is but I have considered a radiant barrier since our 2nd story has no A/C.

Here is an overview; they mention laying the barrier on top of attic floor insulation, which IMHO is a very bad idea without a vapor barrier under the insulation. Even with air holes I would be afraid it will trap moisture migrating from the interior.
http://www.ornl.gov/sci/roofs+walls/radiant/rb_01.html

[lateStarter]

Timely topic for me, as the walls should be up in another week or two. Here, in my part of Poland, most of the newer homes going up have either ceramic tile or steel roofs. Most popular choices seem to be dark red, brown or dark grey/slate. We were thinking of going with dark green, but I may rethink the choice. I would really like to use the snow for insulation in winter and keep it as cool as possible in the summer. BTW, we will have no AC.

I am also looking at getting some fast growing trees in ASAP to help with solar cooling. Amazing what a few well placed shade trees can do for cooling comfort in the summer!

[Pops]

I assume you would want to leave a space at the top and bottom for circulation even with the perforations?

I worry a lot about trapped moisture after repairing lots of dry rot over the years…

[rogerhb]

$this->bbcode_second_pass_quote('WisJim', 'A') black roof (or other dark color) is generally the poorest choice. A dark roof is hotter in the summer, heating the attic and the rest of the house, adding to air conditioning or cooling cost. In cold climates, the snow melts off a dark roof before melting off a light colored roof, and you then lose the insulating value of the snow cover.

[HamRadioRocks]

The roof of the house I'm renting has light gray asphalt shingles, as do most other houses in the area. The house is painted a cream-white color, and the siding is made out of wood. I believe that the vast majority of the daytime heating of the house is due to the asphalt shingles, because the asphalt absorbs heat and the roof gets more direct sunlight than the walls.

On a sunny day like today, the house can heat up by 8 degrees or more from the early morning to early evening. This isn't so bad on a day like today (68 to 76 degrees, so no need for air conditioning), but I need to use the air conditioning A LOT on a day that combines 100-degree heat with an 80-degree dew point and wall-to-wall sunshine. The daytime heating would be even more if it weren't for the big tree in the next door neighbor's yard that shades the house for part of the late morning and early afternoon.

Is there anything I can do to cut down on the heat absorbed by the roof? Since I rent the house, I can't install reflective metal shingles or solar panels on the roof. I'm wondering if it would be a good idea to install a big tarp on the roof and use rope to tie the tarp to anchor points.

[HamRadioRocks]

By the way, the roof is sloped, so a roof garden is not an option.

Yes, I know that a tree that shades the house would help, but a tree takes many years to grow.

[Heineken]

How would the owner feel about your making such an alteration? Better check your lease, or better yet contact him.

Installing a metal roof or solar panels would cost you a lot of money you might never recoup. I wouldn't go that route with a house I was renting.

Maybe you could try painting the roof a lighter color to reflect sunlight. The paint would wear off eventually, but it would last a while and be renewable. A much cheaper, easier, and more realistic option. It won't look very good, though. There's a reason why roof shingles tend to be dark---they look a lot better than white ones.

[HamRadioRocks]

$this->bbcode_second_pass_quote('Heineken', 'H')ow would the owner feel about your making such an alteration? Better check your lease, or better yet contact him.

[Heineken]

Thinking it over, I'd say a white or reflective tarp is your best option---your own original idea. Tie it down well or it will blow off. It will look like hell, though, and the neighbors may complain (if you're living in suburbia).

[xrotaryguy]

I live in Phoenix Az. Many people here install exhaust fans in their attics. The fan can be set up to turn on and off with a thermostat, or a timer, or by hand. This can decrease the temps in your attic from a scorching 140 degrees F to a barely livable 115 F. The temperature differential between your homes living space and the attic will be greatly reduced, and the energy used to run the fan is negligible compared to the cost of running the AC.

Spraying water on the roof will also help. Don't ask me how much. it seems to be that it would be best to spray water on the roof during the hottest part of the day to keep it from getting too hot in the first place.

I have a programmable thermostat in my house that helps out quite a bit. SRP (the local utility) offers a plan that charges the consumer more during peak power demand times, and substantially less during low power demand times. Here is an example of how I take advantage of this. Peak hours are from 1pm to 8pm in the summer months. So, I set the Thermostat at 77 degrees F from 8pm one day, to 2 pm the next. At 2 pm the thermostat goes up 1 degree. At 4 pm it goes up again. At 6pm it goes up one more time. At 8 pm it plunges back down to 77 degrees. We have reduced our electric bill by about 1/3 since the installation of the programmable thermostat. For us, that was a savings of about $50 USD. The thermostat paid for itself in 2 months

[nailud]

The fan idea is probably a good one for your situation. I put a cheep box fan on a timer in the trap door going from the garadge to the attic and blow air up into the attic in the hot part of the day during the summer. It helps.

[Heineken]

It's not exactly true that "tarps don't work," Gideon. They are often used to cover roofs that are leaking, when the owner can't afford reshingling, or to buy time until the roofer can get to work. I've seen tarps remain successfully attached to roofs for YEARS. Obviously they can blow away, if they're not attached right. And all bets are off in a hurricane.

Also, paint will indeed stick to asphalt shingles. Not forever, of course. A roof is a punishing surface. But go out and try it. Paint an asphalt shingle, lay it on the ground, and see how long the paint adheres through sun and rain and time. You'll have a long wait. With a roller for rough surfaces, it would be very easy and fast to paint a roof. I agree that the idea is basically dumb, just like the tarp. It won't significantly relieve the heat problem.

The options you propose are expensive. They probably don't make economic sense for a renter who's trying to save a little on his electricity bill.

You're right that an attic needs to get fairly hot. The reason is to prevent condensation problems, right?

I don't think I'd spend a dime making changes to a house I was renting. Maybe put a powerful box fan in an attic window, if there is one, to pull air through the house.

The best option of all, for the long run, is a tree or group of trees that shade the house. There are some very fast-growing shade trees.

[drew]

$this->bbcode_second_pass_quote('Gideon', '2'). Painting shingles - Really bad idea. I mean REALLY bad. A huge waste of time and money, and unlikely to make much of a difference at all. Further, will not stick to asphalt shingles.

[NEOPO]

Yes, tarps attached with 1x2's every 3-4 feet works fine or as you suggested "with rope at anchor points".

Painting shingles might work yet you would probably have to prime first as most shingles are somewhat porous.

Exhaust/vent fans would work but since you are a renter just get a squirrel cage fan and mount it by the attic exhaust area so if you leave you can take it with you.

Light grey is a neutral color so I do not think going with "white" would reduce the temp that much yet it would help.

Speak with the owner, you may find the owner open to ideas and willing to buy the materials if you do the labor etc etc but then again many do not want any changes made if it involves their money so...

[Pops]

An attic fan makes a huge difference and sticking a box fan in the access door is a great idea in your case – probably your most cost effective solution. Alternately one in the gable vent would work too.

If you have any insulation in the attic already, a radiant barrier installed under the rafters and as instructed would probably be the next more expensive, do the same job as the tarp, be up there forever and not bring the landlord around yelling at you.

Additional insulation if yours isn’t up to the recommendation for your area is probably the least cost effective in your case (again if you have any up there already) because as R value increases it has less and less effect per increment and will take a long time to payback the cost.

But again like NEOPO says I would talk to the landlord who may be happy to help pay some of the costs.

Just my experience…

[Pops]

Oh and since I don’t think it was mentioned, you run the attic fan at night after the heat of the day. Open the windows turn on the fan and it draws in the cool air and pushes the heated air in the house up and out the attic vents cooling the entire house.

In the morning close the windows draw the curtains.

We had an insinuated concrete block house with only a little rock-wool insulation in the attic. it was in Central Ca where it can get over 110*F in the summer and an attic vent was our only cooler for several years.

It made a much greater difference than when we added additional insulation later...