air conditioning

Roofs Going Green

November 21, 2019 By EarthWise Leave a Comment

Green roofs are roofs on buildings that are partially or completely covered with vegetation and a growing medium, generally planted over a waterproofing membrane. The modern version of these roofs began in Germany in the 1960s and spread to many other European countries over time. With concerns about climate change and shrinking natural resources rising, green roofs are becoming increasingly popular across North America. The Toronto-based organization Green Roofs for Healthy Cities estimates that the number in North America has increased by about 15% since 2013.

Replacing black asphalt and shingles with plants can lower the surrounding air temperature, filter dirty storm water, and reduce building energy use. The National Research Council of Canada estimates that a green roof can reduce air conditioning use in a building by as much as 75%. The roofs also help to reduce air pollution and greenhouse gas emissions according to the EPA.

As the benefits of green roofs become more widely known, cities around the world are passing green roof legislation. Copenhagen passed a law in 2010 requiring all new commercial buildings to have green roofs if their roofs are not sloped too much. Toronto was the first city in North America to pass a green roof law in 2009. Over 640 green roofs covering more than five million square feet have since been constructed in Toronto.

Apart from the environmental benefits, green roofs are providing pleasant spaces in the urban environment that may include flower beds, trees, herb gardens, gazebos and picnic tables. As for the economics, studies show that over the course of a roof’s lifetime, green roofs are actually considerably cheaper than conventional roofs taking into account energy savings.

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The Green Revolution Spreading Across Our Rooftops

Photo, posted July 15, 2014, courtesy of Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

A See-Through Heat Shield

January 8, 2019 By EarthWise Leave a Comment

It is estimated that air conditioners use about 6% of all the electricity produced in the United States for an annual cost of $29 billion. With rising temperatures, this expense is only going to get larger.

A significant part of the heat load in buildings arises from heat coming through windows. It turns out that for every square meter of window, about 500 watts of heat energy can be brought in by sunlight, equivalent to 5 old-fashioned light bulbs.

Researchers at MIT and the University of Hong Kong have developed a heat-rejecting film that can applied to a building’s windows that will reflect 70% of the sun’s incoming heat. The film is similar to transparent plastic wrap. It remains highly transparent at temperatures below 89 degrees Fahrenheit. Above that temperature, tiny microparticles embedded in the film shrink and the film becomes more translucent or frosted, still letting in a good amount of light, but rejecting a lot of heat.

There are already so-called smart windows on the market, similar to the electrochromic mirrors in cars that darken to prevent trailing headlights from blinding drivers. But that technology is not very effective in rejecting heat and it requires power to operate, which means you would have to pay to turn windows opaque.

Tests of the new film demonstrated its ability to reject heat and lower temperatures. The researchers estimate that if every exterior-facing window in a building were covered in the heat-rejecting film, the building’s air conditioning and energy costs could drop by 10%. Saving ten percent of tens of billions of dollars is no minor matter.

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See-through film rejects 70 percent of incoming solar heat

Photo courtesy of MIT researchers/MIT.

Earth Wise is a production of WAMC Northeast Public Radio.

Global Warming And Air Conditioners

August 24, 2018 By EarthWise Leave a Comment

All those record high temperatures around the world this summer – such as during the unprecedented heatwave in Japan – put the spotlight on the growing dependence we all have on air conditioning.

City Geometry And Urban Heat Islands

May 16, 2018 By EarthWise Leave a Comment

More than half of the world’s people now live in cities so understanding climate issues in cities is crucial. One of the most important city climate effects which has a profound impact on both human health and energy consumption is the Urban Heat Island Effect.

Bermuda Roofs

September 22, 2017 By EarthWise Leave a Comment

The North Atlantic island of Bermuda is a popular tourist attraction with its pink sand beaches, turquoise water, and pastel-colored cottages with white limestone roofs. The stepped white roofs are not just picturesque, they are highly functional.

[Read more…] about Bermuda Roofs

Breathe Better With Air Conditioning

September 15, 2017 By EarthWise

For many people, commuting to and from work is a time-consuming, stressful part of their lives. In fact, the average American spends nearly an hour a day facing traffic jams and congested highways. There are direct health hazards in commuting as well. Drivers are exposed to increased amounts of air pollutants that have been linked to a wide range of medical problems including cardiovascular disease, respiratory issues and even lung cancer.

The Perils Of Air Conditioning

September 12, 2017 By EarthWise

The battle to reduce greenhouse gas emissions is heavily focused on replacing fossil fuel power plants with renewable energy and replacing internal combustion engine autos with electric cars. But there is another elephant in the room: air conditioners.

Solar Power In Las Vegas

August 16, 2016 By WAMC WEB

The Las Vegas Strip has been referred to as an energy consumption nightmare. Just one look at the place provides evidence for the claim: an endless sea of lights, glitz and glamour and cavernous casinos running huge banks of air conditioning equipment in the desert heat. Even with Boulder Dam a hop, skip and jump away, Vegas is struggling to meet its electricity needs.

Los Angeles’ Giant Battery

August 3, 2016 By WAMC WEB

Los Angeles has decided to replace a major gas-burning power plant with an energy storage device which, if not exceeded by another before it is completed, will be the world’s largest storage battery.

Green Steam

March 9, 2016 By WAMC WEB

Many of the world’s biggest cities have miles of underground pipes built decades ago that provide district energy. District energy systems use a central plant to produce steam, hot water or chilled water that is then piped underground to individual buildings for space heating, domestic hot water heating and air conditioning. As a result, individual buildings served by a district energy system don’t need their own boilers or furnaces, chillers or air conditioners.

[Read more…] about Green Steam

Storing Energy As Ice

December 11, 2015 By WAMC WEB

One of the challenges of operating the electricity grid is that there are times when everybody wants more electricity than usual – like during a hot afternoon in August – and the system struggles to keep up with the increased demand.

Planning Cooler Cities

October 28, 2015 By EarthWise

Anyone who has walked the streets of New York City or Washington, D.C. on a stifling summer day can attest to the fact that cities feel hotter. It’s not a matter of perception.

Female Thermal Demand

September 23, 2015 By EarthWise

If you work in an office, you know the following scenes are not unusual: a coworker wearing a woolly sweater at her desk on a 90-degree day; a woman vigorously rubbing her hands together for warmth in the conference room; or two colleagues engaged in a passive aggressive battle over the thermostat.