Landlording & Rental Properties

Are Your Roofs Cool? An Introduction to Cool Roofs.

56 Articles Written

Occasionally I’m asked to write about some specific green building method or product for real estate investors.  Below is a quick outline on Cool Roofs, one of the most effective energy-efficient measures you can implement if you live in the southern half of the US.

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Cool roofs aren’t new, roofing contractors have used cool roofing products for more than 20 years on commercial, industrial, and residential buildings. For real estate investors cool roofs can be a great solution to save energy in any rental property.  Since they are so durable and aren’t outlandishly expensive they have a pretty quick payback.

They may be installed on low-slope roofs (such as the flat or gently sloping roofs typically found on commercial, industrial, and office buildings) or the steep-sloped roofs used on many homes.

Some benefits of Cool Roofs:

  • Save on annual electricity bills by reducing summer air conditioning costs.
  • Save peak electricity demand costs if you have time-of-use metering (usually just commercial properties fall into this category)
  • Reduce roof maintenance and replacement expenses by extending roof life.
  • Reduce air pollution and smog formation.
  • Reduce roofing waste added to landfills.

White vinyl roofs, which are inherently reflective, achieve some of the highest reflectance and emittance measurements of which roofing materials are capable. A roof made of thermoplastic white vinyl, for example, can reflect 80 percent or more of the sun’s rays and emit at least 70% of the solar radiation that the building absorbs. An asphalt roof only reflects between 6 and 26% of solar radiation, resulting in greater heat transfer to the building interior and greater demand for air conditioning – a strain on both operating costs and your wallet.

One of the ways to make an existing or new roof reflective is by applying a solar reflective coating on its surface. These coatings are specially engineered to reflect heat as regular white paint is not enough.

Ceramic coatings are the most well known in this area and they provide an average reflectance of 75% to 85%. Their application is usually done by trained professionals only but any contractor can be shown how to apply these coatings.

High performance nanotechnology heat reflective paints are the most innovative in this field. They can reflect up to almost 95% of solar radiations, reducing a roof’s heat load by an average of 30% in hot weather with as little as 200 microns in thickness (0.2 mm). Working at nanotechnology levels allows thermal barrier paints like Planet Supra, for example, to offer an unlimited choice of colors in matte or glossy finish (the lighter the color, the higher the performance), easy application like any regular water-based paint and additional benefits such as self-cleaning properties thanks to Titanium Dioxide in the formulation.

Although costs will vary greatly depending on location and local circumstances, cool roof coatings on a low-slope roof might cost $0.75–$1.50 per square foot, while single-ply cool roof membrane costs vary from $1.50–$3.00 per square foot. The cost premium for cool roofs versus conventional roofing materials ranges from zero to 5 or 10 cents per square foot for most products, or from 10–20 cents for a built-up roof with a cool coating used in place of smooth asphalt or aluminum coating.

One of the things I like best about cool roofs is that the methodology is simple (coating a roof) yet the technological advances in the product continue to improve.  I see this as an emerging trend in residential rehabs as the savings are substantial and the payback is strong.

*Many thanks to my venerable intern, Rebecca Sanders, for her research efforts for this article.

    Mark Jacobs
    Replied about 9 years ago
    Great post, Thanks
    Jim Simcoe
    Replied about 9 years ago
    You’re welcome, Mark, glad you liked it.
    Replied about 9 years ago
    I love nanotechnology and the potential that it has for us. What I don’t understand is the surface that this is painted on top of for residential housing. Painted on top of shingles? decking? a layer on top of decking? I hope not to sound too ignorant, but I renovate houses but still don’t have much of a clue. Sounds like an excellent potential for energy and long-term financial savings though!
    Jim Simcoe
    Replied about 9 years ago
    Hi Brooks, Thanks for the comment. Cool roofs can be applied to shingled roofs, decking, etc. It largely depends on the current condition of what’s there now. Feel free to contact me offline if you have more questions, ok? If you are rehabbing houses and flipping or renting them, cool roofs are a great way to up your rents or sales prices.
    Brian Partyka
    Replied about 9 years ago
    Thanks for posting this….you should also consider including metal roofs; How can metal roofing be considered cool when the old adage mentions a cat on a hot tin roof? In simple terms, the less radiant heat your roof system absorbs and the more heat it reflects, the cooler it will be. Cool roofing is measured by two primary standards–total solar reflectance (TSR) and infrared emittance. TSR is a material’s ability to reflect, not absorb, the sun’s radiant energy into the atmosphere so solar energy never penetrates the building envelope. Emittance is defined as a material’s ability to give off heat. For example, a metal wrench lying in the sun is hot to the touch, but a painted metal tool in the sun is easier to handle. The difference is the unpainted metal wrench has a very low emittance, which means it does not effectively emit heat energy. Instead it retains the heat. In contrast, the painted tool has a high emittance and dissipates the heat energy, allowing you to handle it comfortably. This also is true for a metal roof. When the sun sets, a painted metal roof surface emits a portion of the absorbed solar energy in infrared wavelengths into the night sky instead of transferring heat into an attic cavity. Consequently, the roofing cools fairly quickly. A painted roof’s Total Solar Refelctance rating mainly depends on color and type of pigment used. Lighter colors with conventional pigmentation will achieve high TSR ratings; however, recent advancements in pigment technology have allowed the metal construction industry to achieve greater TSR ratings even with darker colors. A metal roof using specially formulated infrared-resistant pigments has considerably higher solar reflectance and infrared emittance without altering the color when compared with conventional pigments used in traditional paint systems. Architects and building owners now have a much wider color range to choose from, including dark grays, greens, deep reds, browns and even black while still achieving “cool” attributes. Metal Roofs also retain 95% of their solar reflectance and therefore resist dirt build up and mildew. Other green facts about metal cool roofs is that they are made of recycled material and can be recycled at the end of their useful life…cradle to cradle!
    Jim Simcoe
    Replied about 9 years ago
    Brian, Thanks for the great comment! You’re right, metal roofs can be another great alternative for roofing. Very good point..Jim
    Jim Simcoe
    Replied about 9 years ago
    Brian, Thanks for the great comment! You’re right, metal roofs can be another great alternative for roofing. Very good point..Jim