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Energy Efficient Roofing Materials

Roofing That Can Pay Back

Energy efficient roofing materials -- the phrase sounds like something out of a government-subsidized report. It certainly doesn't sound glamorous but it's something you should consider the next time you need a new roof, particularly if you live in a warm climate.

When it's time to choose a new roof most people think in terms of what material to choose and matching the color and style to the type of home and neighborhood they live in. However the other factor to consider, one that's either not known or often overlooked is the energy implications of your roofing choice. There's standard roofing and then there's energy efficient roofing. The latter can potentially save you money on your cooling bills while also being a good thing for the environment too.

Another name for energy efficient roofing that you'll see and hear often is "cool roofing" or "cool roofs". The name has nothing to do with the "wow" factor of a home's roof design, but rather, the effect it has on the roof and the home that's beneath it.

Cool roofing (or energy efficient roofing) is simply roofing materials that save energy by keeping both your roof and your house cooler during the warm seasons when you need to use the air conditioner.

So how can something as mundane as a roof be energy efficient? Let's take a closer look.

How Can Roofing Be Energy Efficient?

If you've ever been up on your roof or even touched the roof's surface on a warm sunny day you know how warm it can get. The more the roof is exposed to the sun and the darker its color, the hotter it becomes.

For most conventional roofing materials, that heat is transferred to the sheathing below and into the attic. From there it can permeate into your living space depending on the condition of the insulation. As your home heats up it puts a greater demand on the air conditioning system.

Energy efficient roofing materials minimize that "heat-soak" effect, reducing the amount of heat that's passed into your home. That usually means that it doesn't take as much air conditioning effort to keep your home comfortable.

It's All About Reflectance And Emittance

Energy efficient roofing takes advantage of two properties called reflectance and emittance. In a nutshell cool roofing materials have better reflectance and emittance values than non-cool roof materials.

Reflectance is the ability of a material to reflect the energy from the sun back into the atmosphere rather than absorbing it. It's measured on a scale from 0 to 1 with 1 being the highest level of reflectivity.

energy efficient roofingPhoto Courtesy Of CertainTeed Corp.

When you shop for cool roofing materials look for the term "solar reflectance" on the product's specification sheet. It'll probably be a decimal number like 0.76. You can use that number to compare various cool roofing products.

If there's a down-side to a roof's solar reflectance property it's that it can change over time. Dirt accumulation and normal deterioration of the roofing material will tend to diminish it's ability to deflect the sun's energy. That's why you'll see standards and ratings for cool roofing products based on performance after 3 years of service.

Emittance represents a material's ability to "shed" or give off heat rather than retain it. Like reflectance, it's measured on a 0-to-1 scale with 1 being a higher (better) value. Emittance is also listed in the specifications for energy efficient roofing materials as a decimal like 0.90 and is typically designated as "thermal emittance".


Just like your dishwasher or refrigerator, energy efficient roofing materials can earn the ENERGY STAR label, officially designating them as meeting a pre-set standard for energy efficiency.

To be qualified as an ENERGY STAR roof the material must meet the following minimum criteria:

  • Initial Solar Reflectance - greater than or equal to 0.25

  • Reflectance After 3 Years - greater than or equal to 0.15

These qualifications are for steep-pitch roofs, or roofs that have a rise-to-run ratio greater than 2-in-12. This represents the majority of residential roof designs.

Roofs with a lower pitch are essentially flat roofs and have to meet reflectance qualifications of 0.65 and 0.50 for initial and maintenance values respectively.

energy efficient roofingPhoto Courtesy Of CertainTeed Corp.

Keep in mind that these are the minimum standards to meet ENERGY STAR certification. Other states, local regions or municipalities may enact more stringent specifications for defining cool roofs. For example, California's Title 24 Building Standards Code sets forth more stringent criteria for cool roofing.

The benefit of the ENERGY STAR labeling system is that it provides you with a means to determine what roofing products meet higher energy efficiency standards and in the end, offer better energy-related choices for your home (not to mention the environment).

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The Benefits And Drawbacks Of Cool Roofing

The main reason cool roofing should be one of the considerations in your decision process is that it provides several benefits. But just as it is with any product, there are a few drawbacks as well. Whether the benefits outweigh the drawbacks depends on several criteria and you'll have to be the final judge.

The Benefits . . .

  • Lower Utility Bills
    The less heat that's transmitted into your home from your roof the cooler your home will be and the less you'll have to run your air conditioner. According to the Cool Roof Rating Council, that savings can be anywhere from 7% to 15%.
  • Better Comfort
    Even if you don't use/have air conditioning, a cooler home during the warmer months of the year tends to be more comfortable. If you have a two-story home, the chimney effect (where the warmer air rises upwards) can make the upper floor warmer than the main level. Combine that with a hot roof that transfers heat from above and it can make for some uncomfortable sleeping quarters.
  • Extended Roof Life
    Excessive heat can cause more rapid degradation of your roof, particularly one with asphalt shingles which naturally degrade over time with exposure to the sun. The longer your roof lasts the fewer times you'll need to re-shingle.
  • Possibility For Economic Rebates
    Utility companies in some municipalities offer rebates for the installation of energy efficient roofing. Check with your utility company directly to see if they currently offer a rebate.

    The Cool Roof Rating Council, a non-profit organization chartered with developing methods for evaluating and labeling energy efficient roofing has a listing of rebate programs (link opens in a new browser window) at the 'resources' section of their website. However these listings can sometimes become out of date. You can use them as a first attempt but it's best to check directly with your local energy company to confirm.

The aforementioned benefits are direct benefits, meaning they benefit you directly. Energy efficient roofing also comes with some 'trickle-down' benefits too that are offshoots of the direct benefits.

energy efficient roofingPhoto Courtesy Of CertainTeed Corp.

For example, using less energy because you don't need as much air conditioning is always a benefit to the environment. It reduces electrical demand which translates into less fuel needed to produce the electricity.

Roofs that have longer lives means there's a reduction in the frequency and amount of roofing scrap that goes into landfills when an old roof is torn off and a new roof installed.

Energy efficient roofs also help reduce the urban heat island effect that results from the emission of excess heat from hot roofs in a city environment. The more cool roofs that are installed the less residual heat is given off, keeping overall temperatures slightly lower than would be otherwise. This can have an overall positive benefit in the reduction of an urban area's cooling needs.

The Drawbacks. . .

  • Lighter Roof Colors May Look Dirtier More Quickly
    The lighter colors associated with some cool roof products, particularly some of the light gray asphalt shingles, may develop algae streaks and show dirt more readily. Some asphalt shingles contain constituents like copper to help delay the onset of algae but it won't stave off pollution and other organic deposits.
  • Cool Roofing May Cause An Increase In Heating Needs
    During the winter a home's roof can make beneficial use of any heat energy absorbed from the sun. Cool roofing works against this process and may require an increase in wintertime heating. To what extent is determined by geographic location and the typical characteristics of the winter season like duration, snowfall, and the average number of sunny vs. cloudy days.

On this last point you'll find information from various sources that states that the additional heating energy needed because of the cool-roof effect during the winter is offset by the reduction in energy needs to cool the house during the warm months. That may be true for some climate zones but not all.

If you think about it in terms of annual heating and cooling days you can make your own assessment on whether you live in a climate that has predominantly more heating than cooling needs. If that's the case then the benefits of energy efficient roofing may be diminished.

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What Kinds Of Cool Roofing Choices Do I Have?

First off, not all roofing qualifies as cool roofing. Energy efficient roofing takes advantage of specific technologies and material properties that aren't available in every type of roofing material. Regardless of that fact however there are still plenty of cool roofing products you can choose from.

Cool Roofs - Available In Several Materials & Colors

Cool roofing is available in several of the main types of roofing materials on the market for residential homes. ENERGY STAR qualified roofing comes in metal, tile (concrete, ceramic and composite) and asphalt shingles. Metal tends to have the best reflectance values making it a better choice from an efficiency standpoint.

energy efficient roofingPhoto Courtesy Of CertainTeed Corp.

There's also a reasonable number of colors that you can choose from too, which varies depending on the type of roofing material you choose. The good news here is that you're not locked into choosing white or very light gray.

From a color perspective you'll probably have a wider range of choices (including some darker colors) among the metal roofing products because they generally have better reflectance capabilities. Some tile products also come with a decent array of colors to choose from.

energy efficient roofingPhoto Courtesy Of CertainTeed Corp.

However if you have your heart set on asphalt shingles there are still a surprising number of color choices available. There are some medium browns and grays if you prefer a darker roof color. However there aren't any black or very dark gray colors in asphalt that meet cool roofing qualifications, at least at the time of this writing.

How To Find Energy Efficient Roofing

There are several ways to find cool roofing products. One good source is the ENERGY STAR roofing product web page (link opens in a new browser window) which contains links to either a PDF or MS Excel spreadsheet download that lists all the ENERGY STAR-qualified products.

The nice part about this list is that it's usually kept up to date and contains a comprehensive amount of information. The information included the manufacturer's name, the specific roofing product name (brand and model), the type of material as well as the reflectance values and warranty.

So for example, if you're looking for a cool tile roof, simply download the list (using the Excel format allows you to sort it to your liking), look for "tile" under the material category and check out the products that qualify. From there you can pop the manufacturer and product name into a search engine to find out more information including where to buy the product.

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The other way to find cool roofing is to check out the manufacturers that make the type of roofing you're interested in and see if they offer energy efficient roofing. If they do offer it, they'll make note of it on their website and in their product literature. Products are usually labeled with the ENERGY STAR logo.

Finally, you can contact local roofing contractors in your area and ask them what they offer relative to energy efficient roofing products. Just be sure you do your homework first and understand the facts so you're in a position to ask good questions.

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Publisher's Comments - Is Cool Roofing Worth It?

Whether to choose an energy efficient roof is just one factor to consider when choosing a new roof. The main things you're probably thinking about are getting the best roof for your money along with a product that'll complement the color and style of your home.

That brings up the question of whether it's worth it to even consider cool roofing products as opposed to standard roofing materials. In my opinion it depends on a few things, first of which is where you live.

If you live in an area with a predominance of warm weather and sunny days than I think it's definitely worth considering a cool roof. However, if you live in Montreal, Canada, you might want to do a little more homework because at the end of the day, it might not be that effective for you.

There are a few online cool-roof calculators that can provide you with a "wet thumb in the wind" idea on whether a cool roof makes sense based on where you live and some other particulars about your home and utility rates. These calculators give you an estimate on the economic savings you'd reap with a cool roof.

One is the Oak Ridge National Laboratory roof savings calculator (link opens in a new browser window) for residential buildings. This calculator gives you a range of choices to choose from as well as explanations about what it's asking for so it's not that difficult to use.

The other is the Department of Energy calculator (link opens in a new browser window). It's similar to the one mentioned above but it requires that you fill in the specific criteria for each parameter rather than choosing from a prescribed list that best fits your situation.

The results you get are only as good as the information you put in so keep that in mind.

Otherwise, consider how these other conditions apply to your home to determine whether energy efficient roofing is worth pursuing:

  • Geographic location
    I mentioned it above but I'll say it again -- cool roofs may not be that effective in northern climates. If your heating season is typically longer than your cooling season you may want to invest in more insulation vs. cool roofing. Conversely, if you have 3 or more months of cooling needs a cool roof is worth investigating further.
  • How much (or little) roof insulation you have
    Energy efficient roofing is less effective in homes that have more insulation than less. That's mainly because there's just less heat that's transferred into the house from the roof. If you have little insulation and live in a warm climate, a cool roof may be worthwhile. For the record, an energy audit can tell you whether you have sufficient insulation or not.

    On the other hand, if you have little insulation and live in a colder climate, you might reap more energy savings by adding insulation (because more of your annual utility bills go toward heating rather than cooling).

  • The location of your heating/cooling ducts
    If they're in a non-conditioned space (like in the attic space above the insulation and below the roof decking) a cool roof may be beneficial. But if they're in the walls and floors, areas where the conditioned air in the ducts isn't exposed to high heat, the need for energy efficient roofing diminishes.

Let's take a look at this using a real-world situation. I live in Minnesota in the north-central part of the U.S. When I run a scenario using the energy calculators I mentioned above, I end up with a small net loss if I switch to energy efficient asphalt roofing (going from standard asphalt shingles).

I also have longer periods of heating vs. cooling during the year, typically about 7 months of heating vs. 2 to 3 for cooling (there are periods in the Spring and Autumn where no heating/cooling is needed). My insulation is good and my ductwork is not in the attic. For my specific scenario, it doesn't appear that a cool roof would be to my benefit.

If I lived in Phoenix, San Antonio or Miami, it might be a different story altogether. Your own mileage may vary and you'll need to decide using these kinds of considerations as to whether energy efficient roofing makes sense for your home.

Additional resources on the subject of cool roofing can be found at the following websites (these links will open in a new browser window):

Cool Roof Rating Council (CRRC) - non-profit organization focused on education and evaluation of energy efficient roofing

U.S. Environmental Protection Agency (EPA) - article on cool roofs with links to more information

ENERGY STAR Roof Products - ENERGY STAR website page on energy efficient roofing products

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Here's More Related Info That Might Be Helpful...

A Choice Of Roofing Materials - Discover what other options you have when it comes to putting a roof on your house and the highs and lows associated with each type.

Asphalt Roofing Shingles - It's one of the most prevalent types of roofs you'll see but there's more to choosing an asphalt roof than you might think.

Faux Slate Roofing - Slate roofing is a durable and long-lasting roof but it's expensive and requires skilled labor. This article shows you faux slate roofing options that mimic the look of slate but offer some savings over real slate.

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