We’ve all heard the old adage, “You can’t judge a book by its cover.” Well, you can’t always tell just by looking whether a home is energy-efficient or not. But the roof is one place where efforts to reduce fossil fuel demand for home heating and cooling are on full display. White paint, rooftop gardens, and solar panels are three ‘cool’ toppers that are becoming increasingly common.
- White paint: This option is most popular in the tropics and in urban areas, where the prevalence of black pavement and dark roofs leads to extra heat trapping – known as the urban heat island effect. In this setting, painting roofs white has been suggested as a low-cost way to increase the amount of sunlight (and thus, heat) that is reflected back away from the Earth’s surface. While white roofs alone certainly won’t solve our climate woes, a recent analysis by researchers at Lawrence Berkeley National Laboratory in California indicated that whitening both roofs and roads in cities with populations of a million or more could be the equivalent of eliminating two years worth of global greenhouse gas emissions (using 2006 as the year).
- Rooftop gardens: Also known as green, live, or living roofs, rooftops that are at least partially covered in vegetation have a number of benefits. They can reduce stormwater runoff by absorbing rainwater; provide extra insulation and – like white roofs – increase reflectivity to reduce heating and energy usage; create habitat area for native plant and bird species threatened by human development; provide local food; even serve as water filtration systems and carbon dioxide traps. Again, green roofs, alone, won’t solve the problem. But a rooftop garden may be several degrees cooler than neighboring traditional roofs on a hot day, and one study in Canada found living roofs provided enough insulation to reduce both heating and cooling demand by a quarter.
- Solar panels: The sun’s energy can be captured to provide either hot water or electricity, and not just in the tropics. Real-world experiences and at least one scientific analysis indicate that solar panels can power homes throughout much of the year, even here in foggy coastal New England. Of course, solar panels themselves are made of some rather nasty materials whose mining, use, and disposal all can be problematic.
There’s also the issue of aesthetics. With the possible exception of living roofs, whose predecessor – the sod roof – has a centuries-long history in certain parts of the world, these roof toppers lend a decidedly contemporary look to a home. In areas, like Cape Cod, with a strong historical aesthetic, revamping one of the most visible parts of a house can be controversial. One resident of a local historic district told me it took her three attempts to get her solar installation accepted by the Historic District Commission in her town.
But when it comes to both living roofs and solar panels, the price tag is probably the biggest obstacle for most homeowners. Installation costs can run into the tens of thousands of dollars, and homes may need significant structural work to handle the weight of rooftop additions. Of course, proponents argue that these projects pay for themselves in the long run with energy savings, even excess production in the case of solar panels. But the upfront costs remain a formidable hurdle.
If you’ve spent the time and money to make your roof cooler, how have you financed your project? And what benefits have you seen?