Dear EarthTalk: I've heard that simply painting your roof white can reduce household electricity bills by 40 percent. Is this something any of us can do? -- Susan Pierson, Sumter, S.C.

Yes, anyone can do it -- and the benefits can be significant, especially for those in warmer climates who expend a lot of energy keeping cool. But most of the world's roofs, including on some 90 percent of buildings in the U.S., are dark-colored.

Dark colored roofs absorb more heat from the sun's rays than light colored ones, and as such get much hotter. A black roof exposed to full sun can increase in temperature by as much as 90 degrees, meaning the air conditioning inside has to work that much harder to compensate for the added heat load.

But a white or reflective roof typically increases temperatures only 10 to 25 degrees above ambient air temperatures during the day. This translates into a savings of up to 15 percent on air conditioning energy use over a year for a typical one-story residence, according to the U.S. Department of Energy. The upshot of this energy savings is not only cost savings for the consumer -- annual energy bill savings of 20 to 40 percent aren't uncommon for single story homes in America's Sun Belt -- but also reduced air pollution and greenhouse gas emissions generated in the production of electricity.

A white roof also helps keep buildings and houses without air conditioning cooler in the summer than they would otherwise be. And it also helps mitigate the "urban heat island effect" whereby a city can be 6 to 8 degrees warmer than its surrounding areas on warm summer days.

The nonprofit White Roof Project promotes the concept across the U.S. and last year painted some 30 buildings, helping hundreds of families lower their energy bills in the process.

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"A white roof project is low cost, easy to implement, relieves stress on the power grid, cuts down on smog, and creates tangible change for individuals, our communities, and even globally," reports the group, which is looking to expand its work across the country significantly in 2013 and expand internationally in 2014.

The White Roof Projects gives away instructions (via a free downloadable DIY packet) to help do-it-yourselfers paint their own roofs white without hiring a painter or roofer. All it takes is a few painting supplies, a couple of cans of highly reflective elastomeric white paint, and a plan for how to cover all relevant surfaces properly and safely. Those who would rather hire someone to do the ladder climbing and paint application can hire any local painter or roofer.

While green roofs may be preferable from a strictly environmental perspective in that they contain plants that filter pollutants and reduce run-off, white roofs may indeed provide more overall environmental benefit for the cost of a couple of cans of special white paint. Indeed, painting the roof white might be the best energy efficiency improvement you can make to your building or house.

Contacts: White Roof Project,; DOE Cool Roof Fact Sheet,

Dear EarthTalk: What exactly are "citizen scientists" and how can I become one? -- Eric Wilson, Barre, Mass.

"Citizen scientists" are members of the public who help scientists and researchers by making observations and/or collecting and recording data. The term was first popularized by the National Audubon Society as part of its annual Christmas Bird Count (CBC), during which volunteers from across the country fan out to count local birds. The aggregated data has been helping Audubon assess the health of U.S. bird populations and plan its conservation initiatives accordingly since the tradition began in 1900.

Thousands of Audubon members still participate in the CBC, though modern-day citizen scientists are more likely to be members of Project Noah, an app-based tool that allows everyday people to share wildlife sightings via their Internet-connected mobile devices. Through the power of so-called "crowd-sourcing" (outsourcing a task to a distributed but undefined group of people), it has become one of the most popular online communities for nature exploration and documentation. User-created local missions allow members to observe specific wildlife species based on their own interests, accessing the efforts and enthusiasm of other Project Noah members in the process. And of course, individuals or small groups or classes can search for other missions to help via Project Noah's website or mobile app.

Some other examples of environmentally oriented citizen science include, an online community of amateur and professional naturalists who share observations of insects and collaborate on related research, and Citclops, a European Union-funded project where everyday people help scientists gather data to assess the environmental status of water bodies across that continent.

Budding citizen scientists looking for different types of projects can browse the offerings on Zooniverse, a citizen science web portal that grew out of the online crowd-sourced Galaxy Zoo project, whereby amateur astronomers help classify the morphology of galaxies. More than 700,000 volunteers have so far contributed time to various Zooniverse projects. Many Zooniverse projects pertain to space and astronomy, but green-leaning citizen scientists will find plenty to pitch in on there. For example, analyzing wartime ship logs to better model Earth's climate, categorizing underwater calls from endangered killer whales to help identify and track family groups, or identifying African animals "caught" on millions of camera trap pictures.

According to Zooniverse, conducting research by using citizen science has several advantages. One is the ability to cope with extremely large data sets so that researchers can access many person-years' worth of classifications within days, weeks or months. Another is the fact that so many multiple independent interactions with the data sets help highlight quantitative errors and also serve as great training regimens for how to incorporate machine learning approaches to classification problems.

"While the primary goal of our projects is to produce academic research, by their very nature they are also outreach projects," reported Zooniverse. "As it involves our volunteers directly in the process of research, citizen science is a powerful tool for both formal and informal education."

Contacts: Audubon CBC,; Project Noah,;,; Zooniverse,

EarthTalk is by Roddy Scheer and Doug Moss of E -- The Environmental Magazine ( Send questions to