'Cool' roofs – a hot idea?
This hidden-in-plain-sight upgrade can mean saving on your electricity bills and enjoying a much more comfortable home during hot summers.
© MCA Superior Roof Tiles; Custom-Bilt Metals
Linda Hanson is accustomed to long, hot summers, and she wanted to find a new way to reduce her cooling costs.
Hanson owns a home in Canyon Lake, Calif. "The average temperatures out here are well in the 100s all summer long, so our (electricity) bills were $800 a month. It was pretty outrageous. We could not cool the house down. We'd run the air conditioner all the time."
A big problem was the original concrete tile roof, which sat on the rafters and radiated that heat right into the house.
Then Hanson and her husband swapped out that roof for a so-called "cool roof" of green tiles on their 3,000-square-foot house. (They made other improvements, too, such as upgrading the home's windows and adding attic insulation.)
"We also put a swimming pool in, and even with that swimming pool, with the filter running, our bills in the summer are probably 200 bucks a month less," she says.
The best part, she says, is "my house is comfortable all the time."
- On our blog, 'Listed': What if your thermostat is smarter than you are?
Hanson's savings may be dramatic, but they illustrate the point: Installing a cool roof is a hidden-in-plain-sight way to cool your home, shrink your electricity bill and help the planet. It's such a simple, smart idea that Energy Secretary Steven Chu endorsed the idea in a meeting with Nobel laureates last year.
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An old idea made new
Inhabitants of places such as Bermuda and the Greek isle of Santorini have long known that painting their roofs white to reflect sunlight can keep their homes cool. Studies bear that out: While black surfaces such as traditional built-up asphalt shingle roofs can reach 185 degrees, a roof that's white can be up to 70 degrees cooler because it bounces so much sunlight back into space.
"The science of it is very basic," says Hashem Akbari, a leader in the study of cool roofs and a professor at Concordia University in Montreal.
- MSN Living: 5 ways to save money on air conditioning
White roofs make sense particularly on commercial buildings because those buildings have their cooling systems on most of the year as computers and other machinery inside them create heat, says Chris Scruton, a project manager in the California Energy Commission's research program in building energy efficiency. With a white roof, "As much as 75 or even higher percent (of sunlight) can be reflected," Scruton says.
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Choose your hue
That's great, you say, but what if you don't want a white roof on your Colonial?
You're in luck. There's a roof for you, too.
Manufacturers can make colored cool roofs that stay much cooler than traditional colored roofs. They add pigments or glazing to roofing materials that reflect infrared light back into space. That unseen infrared light makes up 52% of light that falls to Earth; we can't see it, but we feel it in the form of heat.
These cool roofs can take the form of tiles, shingles or metal. California's MCA Clay Roof Tile, for instance, makes 33 cool roof tiles, with reflectiveness ranging from just over 30% (for many of the dark-hued tiles) to 76% (for "White Buff"), says Yoshi Suzuki, president and CEO. Traditional dark asphalt roofs only have about 5% to 15% reflectiveness.
"People are starting to catch on" to the benefits, Suzuki says, but "it's not so much residential yet." In 2007, about one-quarter of the commercial roofing market consisted of Energy Star-rated (that is, highly efficient) roofing products, compared with about 10% of the residential market.
If your winters are cold, but relatively sunny, you could partially compensate for loss of solar heat from a white roof by painting the south-facing wall of your house a dark color, or cover it with dark tile or brick. Cut out a new window or two on that wall for more solar heat. Of course this would be effective only if structures or trees don't block the winter sunshine.
I want a cool roof in the summer, but our current roof in the winter. The sun's heat makes a huge difference during the winter, but is a huge bother during the summer. I'm considering rigging white canvas somehow over our small south facing roof in summer......haven't even checked into prices, yet, as we just replaced our 73 year old windows.
The two biggest areas of heat/cool loss and gain are roofs and windows. THE FIRST THING YOU DO IS INSULATE!!!! This is the biggest payback and often the least expensive. Having a properly insulated AND VENTED attic space is critical. The most important thing you can do is insulate that attic!!! Current building codes only require about half the venting an attic really needs. Attic fans can really be great as well as whole house fans. New windows with thermo-panes and low E may or may not be a cost effective item. I, for instance, have very outdated windows but have pretty good triple track storms. At this point in time, it is not cost effective for me to change them. I do not use enough cooling to even come close to replacing them and can too easily and cheaply run plastic on the inside with the window kits. I can buy and install the window kits for 100 years before I would get my money back on the windows. It is about being efficient AND cost effective.
Since I am in the business, I get rather miffed over all of the green stuff we hear about. Much if it isn't green at all and many of us in the business have been installing ultra high heating equipment for for 30 years. I have been installing 92% efficient heating equipment since 1980. We can now get up to 98% on some units. Don't think for a minute that the Europeans are ahead of us on technology. They have focused on boilers while in America we have focused on furnaces. That is simply an issue of quantity. As far as tankless water heaters go, I have an old side arm MorFlow tankless (now owned by Bradford White) that is older than me, and I am older than dirt!!!! This is actually new/old stock. I think I may still have the box for it as well. Any way, the US doesn't lag behind, it is simply a question of economics and politics.
I've lived in a '67 hot box mobile home now for 13 yrs, in NW New Mexico, with no intention to do so except for a couple of years. It's poorly insulated in the ceiling for sure. It gets nearly 100% southern exposure with no trees on the south side, but has some nice tall evergreen bushes on the west end.
Even though I own the MH, I rent the space so I haven't been very interested in investing much into either for several reasons.
Good gosh I sure don't like to see the summer go with the awesome weather but my goodness the radiant heat is nearly unbearable mid summer, and it's basically impossible to keep it at 70 deg in the winter unless the furnace runs nearly constantly and eats the heck out of the Natural gas and Electricity.
First of all I shouldn't have chose to live in a MH, but it is within 5 min walking distance to work; since it is in a confined park; with just about 3 feet of space between the MH and the south side fence, that has it kind of limited the planting of some vegetation to block the sun in the summer and let it come in fully in the winter; especially at the high angle of summer.
And actually the first and foremost thing; I should have insulated the ceiling/ attic area the first thing, regardless of 2 years outlook.
On the other hand; my Dad and I built a 2700 sq ft home out of cinder- block, concrete and stone and massive timbers; that is roughly 50% under-grade/ under-ground, and the differences are phenomenal. Truly. And this my be of no help to those that have existing homes that need modifications and/ or not the ability or drive to do so, but it is remarkable.
Use of doors and other air barriers is very helpful to sequester the living spaces. This sounds menial and elementary but let each reader make adjustments and understand that it is not meant to be a condescending statement. It's only meant to be helpful.
Some good forethought's, some light framing products and thought, plastic sheeting (low-toxin) some strips of cardboard and or wood veneers and a staple gun or other fastening tool/ 's.
Always make sure that the exits are understood by all!
Wow a house that floats and self powers; and rides up 12 posts to adjust to rising floodwaters. Point of concern: what happens when the water does not rise equally from all points in a manner conducive to a lab test, what happens with hydraulic force and side shear, has aqueous cementation and equilateral balancing been factored in, WHY NOT JUST NOT BUILD IN A FLOOD PLAIN!!!
Those of us that belong to the Common Sense Minority would like to suggest this idea:
Anyone dumb enough to build where a natural disaster is a prevalent enough factor to get written into your insurance coverage needs to either post a surety bond for value of the home, or forsake coverage of an event that is statistically likely to remove your home and cause the rest of us to have elevated rates.
Roof systems sound great if i ever move and need a new roof, but currently I have concrete shingled (lasts forever) roof on a 2 story 5400 ft dutch colonial in VA and summer heat absorption was big problem on the second floor, even with a power gable attic fan and good insulation. So I installed "radiant barrier" on the underside of my rafters to keep the heat out and over the attic floor to keep the heat in. It made a huge difference. My electric bill just dropped from $325 in June to $211 in July, don't know the winter results yet but I expect even better! I also just put window film on my south facing windows. I highly recommend both!!!!!!!!
The best thing you can do is put in a powered ventilation fan in the attic since it can reach over 140 degrees in the summer. It vents the heat in the attic (not drawing air through living area of house) just through the attic. I planted trees that have since matured and shade some part of my house most of the day and completely in the shade by 4:00 in the afternoon. My central AC went out three years ago so I bought a window unit. Not quite as good as central air but keeps me comfortable. I'm cooling 1,400 sq feet with a $300 window unit which adds about $30 a month to my electric bills. It can keep me at 76 degrees when it is in the upper 90's outside in Atlanta. Attic is well insulated.