This high-rise green roof in Washington DC required a large crane to lift the soil and gravel onto three floors. (Photo courtesy of DC Greenworks)
Green roofs are increasing in popularity across the US, especially in cities, where
there’s not a lot of space for gardens. Sabri Ben Achour explores the trend in
Washington, DC, where the city government is promoting the practice for it’s
environmental benefits:
Transcript
Green roofs are increasing in popularity across the US, especially in cities, where
there’s not a lot of space for gardens. Sabri Ben Achour explores the trend in
Washington, DC, where the city government is promoting the practice for it’s
environmental benefits:
In Washington, you can see flowers and vegetables growing on top of homes,
businesses, even government buildings throughout the city. DC officials say
Washington has nearly 70,000 square feet of rooftop greenery. Only Chicago has
more.
One big fan of these so called green roofs is a popular small hotel, Tabard Inn, just a
few blocks from the White House.
“There’s about 10 varieties of sedum on this roof.”
Sarah Murphy is giving a tour. She’s a horticulturalist.
“This is a very pungent oregano here on the corner, it looks heavily used.”
The city of Washington pays building owners about one-fourth of the cost of
incorporating greenery on rooftops. One big reason? Rainwater runoff.
Sarah Loveland works for an environmental consulting non-profit called DC
Greenworks.
She says Washington has what’s called a combined sewer system. The sewer
system doesn’t just take in what’s flushed down the drain, but also all the rain
running off roofs and streets.
“If you imagine that our sewage treatment plant has a dam, and the sewage system
combines with the storm water system before the treatment plant.”
So, when there’s a heavy rain, that dam at the sewage treatment plant overflows.
“You have both raw sewage and runoff from the streets going directly into the river
untreated.”
Three billion gallons of it a year, at one point.
The EPA sued the District of Columbia.
The city had to spend $150 million to address the problem. Part of that money goes
to green roof grants.
The green roofs slow down rain water – give it some place to soak instead of just
running off straight down the gutter. The city says roofs in the city prevent a million
gallons of storm water runoff from entering the Potomac River.
The roofs also insulate buildings – especially during the summer. Some studies
show they reduce energy costs by 20-30%. And they reduce the heat island effect in
the city, since they don’t get blisteringly hot like traditional roofs.
Green Roofs even offer some habitat for creatures, like bees.
Sarah Loveland with Greenworks, the consultant agency, says rooftop gardens are
also increasingly popular for growing food.
“Veggies are really popular, herbs are really popular – this is a trend that’s taking off
in the restaurant industry. There’s a lot of buzz around it.”
Blueberries and herbs abound in the rooftop gardens of the Tabard Inn, where Paul
Pell is executive chef.
(sound of celery chopping)
“Yeah, we go up and get whatever we want, so it’s fresh. We just climb out the
window when we need it. Chocolate basil goes with ice cream, nasturtiums go with
soups and salads.”
Washington has an advantage over some larger cities in its promotion of rooftop
gardens because federal law prohibits skyscrapers in the nation’s capital, so most
buildings don’t cast shadows over their neighbors.
As a result, most rooftops are sunny – all they need is greenery to soak up the rays.
For The Environment Report, I’m Sabri Ben-Achour.
