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Community and Q&A

Is there a roof colour that is better for the environment overall?

user-6809777 | Posted in General Questions on

We are building a house in Zone 4 just over the border in Canada. We are going with a single slab roof with a 2.5:12 pitch that angles to the east and will use metal as our roofing material. We thought we had read (somewhere, can’t find it on the internet) that lighter coloured roof material can act like snow/ice and reflects sunlight back into space, therefore is better for the environment overall from a global warming perspective. Just wondering if there is any consensus out there in the GBA community on that. Just as a note: the microclimate where we are building is predominantly cool and rainy, and air conditioning isn’t used in that area so a lighter roof wouldn’t save on any energy costs. Thank you very much for any responses.

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  1. GBA Editor
    Martin Holladay | | #1

    User-680977 [by the way, what's your name?],
    I'm assuming that you live near Vancouver, BC -- the only part of Canada (as far as I know) in Climate Zone 4.

    The short answer to your question is that roofing with a high solar reflectance (ability to reflect sunlight, measured on a scale of 0 to 1) and high thermal emittance (ability to emit thermal radiation, also measured on a scale of 0 to 1) will reduce global warming. Whether a single roof matters much (when it comes to global climate change) is a matter of speculation. If every roof in an urban area complied with "cool roof" specifications, the combined contribution of all of those cool roofs would reduce the heat island effect.

    Generally speaking, most "cool roofs" tend to be white. That said, pigment manufacturers have developed paints that have a high solar reflectance and a high thermal emittance (and therefore qualify as "cool roofs") that appear dark to the human eye, so those who want to install a "cool roof" aren't restricted to white roofing.

    As you accurately note, a cool roof won't save you money on your energy bill. Especially on a new home with adequate insulation and ducts inside the home's thermal envelope, the reflectance and emittance of the roofing doesn't affect energy bills very much.

  2. user-2310254 | | #2

    Are you trying to have your home certified as energy efficient? Some programs award points for installing a cool roof.

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