Lidija Grozdanic

New Study Shows White Roofs are Three Times More Effective than Green Roofs at Fighting Climate Change

by , 02/11/14
filed under: global warming, green roof, News

white roofs, white roofs climate change, sustainable white roofs, green roofs, scientific study, eco-friendly roofs, roof gardens, climate change, Lawrence Berkeley National Laboratory, Stanford University study, environmental study, heat island effect, reflective roofs

Green roofs offer a lot of environmental benefits – they provide additional insulation, reduce rainwater runoff, and can lower your electricity bill. However a new study suggests that roofs painted white might actually be more effective at fighting climate change. A study published in the Energy and Buildings Journal compared three types of roofs – green, black and white – and came to the conclusion that white roofs have great economic benefits, and they are also three times more effective than the other two at fighting climate change.

white roofs, white roofs climate change, sustainable white roofs, green roofs, scientific study, eco-friendly roofs, roof gardens, climate change, Lawrence Berkeley National Laboratory, Stanford University study, environmental study, heat island effect, reflective roofs

Researchers at the Lawrence Berkeley National Laboratory conducted an economic analysis of the costs and benefits of white, black and green roofs and found that white roofs are far superior in fighting climate change than the other two. While roofs painted black absorb heat and contribute to the urban heat island effect, white roofs reflect the sunlight back into the atmosphere and help cool down its lower parts. The study advises those concerned with global climate change to choose white roofs, adding to a host of other studies in the past decade that have allowed the “white roof movement” to gain momentum across the United States. However, things are not as simple as they seem.

A series of climate simulations carried out by Mark Z. Jacobson and Ten Hoeve of Stanford University showed some unexpected results. Despite their beneficial effects on the lower parts of the atmosphere, white roofs decrease the temperature difference half a mile above ground-a difference which drives cloud formation and less clouds means more sunlight reaching the Earth’s surface. This, among other issues like the impact on fossil fuel consumption and summer cooling vs. winter heating gains, is still subject of scientific debates. Meanwhile, it should also be noted that vegetated roofs offer built-in storm water management mechanisms in addition to some cooling benefits.

Although we are excited to find out how different roofing strategies may affect climate change, one should be aware of the fact that these investigations involve a wide spectrum of factors and potential consequences far too complex for a hotheaded (pun intended) thumbs-up verdict.

+ Energy and Buildings Journal

+ GATOR-GCMOM Environmental Model

Via Fast Co.Design, Huffington Post

Images from Shutterstock and The White Roof Project

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7 Comments

  1. scicdb3 February 6, 2014 at 5:00 pm

    Just painting a roof white will have only modest effect: what is important is the material in the paint that allows the re-radiation and reflection.
    In Perth we chose a black roof because (amazing as it sounds) you spend more money heating a house than cooling it, so black with its absorptive properties was better than one with reflective properties.
    One can also look at unglazed terracotta roof tiles certainly in the tropical climates – the cooler night allows moisture to condense into the tile itself, and in thee day it takes considerable latent energy to drive this off before being able to heat up the roof thus reducing A/C loads through the roof.

  2. Bob Ellenberg February 6, 2014 at 4:57 pm

    I like vegetated roofs but don’t consider them very “green” other than their natural color. If you are where you could collect and reuse the water that falls on the roof, a green roof won’t give up hardly any of it. And if you have a dry spell you can end up using a lot of water to keep the plants alive. It requires a lot more structural strength to hold up dirt and I don’t see anyone calculation the impact of the additional building materials. Lastly dirt is not an insulator so you still need about the same amount of insulation below it. I’m not opposed to vegetated roofs but look at all aspects when making comparisons. The Building Science Corporation has an article at their website on why they consider the “green” aspect of them to be hypocrisy but discuss what they consider the real benefits (they like green roofs too).

  3. rick suddes February 6, 2014 at 4:16 pm

    Why does it a group of overpaid people doing research on this subject spending a lot of goverment money for nothing! I have had a white roof for over 30 years. On heating & ac filters the goverment
    still let filters on the market you can read a newspaper through!
    If you use only MERV 8 filters and up on all heating & ac systens the savings would be about 25 Billion per year! But the dumb goverment and congress will not address the problems! It is all about MONEY & CONTROL! Solar does not pay unless the sorry goverment pays to support it.

  4. rlsauer February 6, 2014 at 3:38 pm

    Do you mean green colored roof or are you speaking of a planted green roof? Totally different!!

  5. Stefan Doering February 5, 2014 at 8:30 pm

    This is fascinating. I would imagine there are many, many benefits to green roofs that are not directly integrated into the calculations of green vs. white roofs.

    As the article states, it is not an easy answer and the jury is still out on which is better for combating climate change.

  6. Justin Dolan February 4, 2014 at 11:53 am

    Really? Can you go into detail on how allowing more sunlight through clouds as a better effect on the climate than a green roof house that doesn\\\’t need electricity for heating or cooling? I build living roof homes and white roofs in Costa Rica. The cloudy days are nice here. I still love and promote white roofs (especially ones that collect rainwater like ours). As someone that builds both types of roofs and owns them both, I would go on record as saying they both have their places in sustainability but, living roofs not only benefit the environment, they benefit the owners of the building more than a white roof.

  7. Keith Poole February 3, 2014 at 11:26 pm

    so white roofs somehow convert more co2 into oxygen than plants on a green roof? this doesnt make any sense.

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