I don’t know if any of you are quite as crazy as I am and dream of someday owning a house with a green roof (and I mean an actual growing, living, planted, green roof), but if you’re not quite ready to make that leap, then maybe your green roof could be white instead...
When the sun is shining and you’re headed to the beach do you wear dark or light colors? Of course, you grab that light colored shirt because the dark one would be too hot. The light shirt is cooler because it has a high albedo, or reflectance. By reflecting the heat of the sun you stay cooler.
Your roof is no different. When the sun shines down on your roof it absorbs heat, and dark roofs absorb much more heat than light ones. I’m sure you’ve been in an asphalt parking lot in the summer time and noticed how hot it is. Many roofs are made of similar materials, and they get just as hot. These hot roofs clustered together in dense urban areas contribute to what’s known as Urban Heat Island Effect (UHI), which is a warmer zone typically found around cities.
Now, the point of all this is that when your roof absorbs lots of heat energy, two things happen: First of all, the inside of your building heats up, and the air conditioning has to work harder to keep it cool. This uses more electricity, releases more green house gasses from power plants, and runs up your electricity bill. Not to mention, contributes to global warming. Second, by not reflecting heat, the building retains it, and we experience UHI. Now that the city is even warmer we need to run even more air conditioning, and we’re back to the beginning. Are you starting to see a connected cycle?
The solution to this issue may be simpler that you think. Applying a white elastomeric roof coating, or installing white shingles will raise your albedo considerably, and provide a lasting solution. These are great options when it comes time to replace a roof, but until then, you can make a change right now for a whole lot less money. Get up there on that black roof with a couple buckets of exterior grade white paint. It will provide a temporary solution and reduce your immediate solar heat gain until it’s time to make a more permanent fix for your roof.
-Scott
Image via Flickr member Klearchos Kapoutsis licensed under Creative Commons.
© 2009 Apartment Therapy
Love this! Thanks, Scott!
view neefall's profile
This is fantastic! Really good information to have.
view mlena's profile
Great article for people who probably didn't realize what simple measures they can take to make a big difference.
view booker1820's profile
I just put a new roof on my garage and porch... unfortunately I was trying to match the mid-range gray that is on the rest of the house so I didn't quite go with white. Not to mention that my house is beige and that would be hideous, but I see your point and think it makes great sense. I have been interested in solar shingles for a while and always thought I would put them on the main roof when it comes time... but it looks like I won't be in this house that long so it'll have to wait until the time is right.
Keep up the good work!
view todd403's profile
Have to have a new roof put on soon . . . so I'll think about this. Just have to come up with the courage to be "different" in my neighborhood. Peer pressure to have those dark roofs. OK, I'll be the trendsetter . . .
view connie5400's profile
OMG what a great idea! Thanks so much! I'm going to Home Depot right after work to buy paint and I'm gonna spend my weekend painting my roof! I'll have to paint my mail box to match... It may look like there's snow on my roof like 24/7/365 daysperyear...but my heat and electric bill is totally redonculous due to global warming and the war and terror and junk. You should go into the Green roofing business, you'll make millions...and you'll be a hero.
Just visited this place in SF this summer...check it out.
http://www.greenroofs.org/index.php?option=com_content&task=view&id=1039&Itemid=136
view Morgazm's profile
I never thought of this as an urban thing but always associated white roofing with exotic getaways like Mykonos, Greece and the like. It'd be great to get management companies and our landlords on top of this kind of thing here in Boston. Let's face it, as the second youngest city in America, the majority of us are the future ... and even though most of us don't own, we could use this info to rally for greener design. Besides, what landlord wouldn't wanna cut costs??
view tmstew's profile
Interesting stuff, Scott. Who knew you were such a scholar?
view christopherldunn's profile
Really interesting especially as a city dweller. We should all advocate with our building management to take action! Thanks Scott.
view lisakaufman's profile
What? You mean "silvercoating" your roof? Row house dwellers have been doing it for ages. Still, a good idea.
view Arkay's profile
I like simple inexpensive things. Thanks Scott!
view JoanieH's profile
Nice clear and concise explanation of an important concept. Hope it goes far and is well used!
view deborahlena's profile
Great Article! I think that this should be a push for building owners in major urban areas even more than just individuals.
view chicagoooo's profile