Green Roofs in DC

Walk around DC on a clear, sunny day when the cherry blossoms are in peak bloom and it doesn’t take long to realize what a beautiful city we have. Looking at it from a satellite image on the other hand – not so attractive. What do you see? Mounds of concrete, tangles of asphalt, tar roofs, cement buildings, essentially a nonporous, concrete jungle.

DC, along with many major cities tends to be significantly warmer than the surrounding suburbs as a result of this  concrete jungle. This phenomenon is know as the Urban Heat Island effect (UHI). This excerpt from the EPA’s website helps to better understand the effect:

Heat islands occur on the surface and in the atmosphere. On a hot, sunny summer day, the sun can heat dry, exposed urban surfaces, such as roofs and pavement, to temperatures 50–90°F hotter than the air, while shaded or moist surfaces—often in more rural surroundings—remain close to air temperatures.

90°F hotter!?! That’s insane!

In addition to DC being warmer, the concrete jungle has a second sinister drawback – stormwater runoff. As it rains in DC, as little as a half an inch of rain can overwhelm our combined sewer system, causing it to spew RAW sewage (yes, poo poo and pee pee!) into our waters! Enjoy your evening swim…

Stormwater runoff as it travels back to the waterways also collets, gasoline, fertilizers, nitrogen, bacteria, pesticides, sediment, trash, metals, all kinds of harmful things and deposits them into the water.  The result –  a polluted Washington Chanel, a less than healthy Tidal Basin, a murky Anacostia River, a contaminated Potomac River… you get the picture.

In comes ecospaces and green roofs to save the day! With green roofs, rainwater is stored by the growing media and then used by the plants from where it is returned to the atmosphere through the processes of transpiration and evaporation. Check out some of these other critical benefits green roofs provide according to Green Roofs for Health Cities a non-profit that promotes the industry:

Stormwater Management

  • In summer, depending on the plants and depth of growing medium, green roofs retain 70-90% of the precipitation that falls on them; in winter they retain between 25-40%.
  • Green roofs not only retain rainwater, but also moderate the temperature of the water and act as natural filters for any of the water that happens to run off.
  • Green roofs reduce the amount of stormwater runoff and also delay the time at which runoff occurs, resulting in decreased stress on sewer systems at peak flow periods.

Moderation of Urban Heat Island Effect

  • Through the daily dew and evaporation cycle, plants are able to cool cities during hot summer months and reduce the Urban Heat Island (UHI) effect. The light absorbed by vegetation would otherwise be converted into heat energy.
  • UHI is also mitigated by the covering of some of the hottest surfaces in the urban environment – black rooftops.
  • Green roofs can also help reduce the distribution of dust and particulate matter throughout the city, as well as the production of smog. This can play a role in reducing greenhouse gas emissions and adapting urban areas to a future climate with warmer summers.

Improved Air Quality

  • The plants on green roofs can capture airborne pollutants and atmospheric deposition.
  • They can also filter noxious gases.
  • The temperature moderating effects of green roofs can reduce demand on power plants, and potentially decrease the amount of CO2 and other polluting by-products being released into the air.

Does it make sense yet? The benefits above only speak to the environment. Green roofs also reduce the heat flux through your roof, and less energy for heating or cooling can lead to significant cost savings. They also prolong the life of your roof’s waterproofing membrane since the plants and growing media bear the brunt of the elements.

Now, how does it all tie together? In a perfect city every roof would be green. DC would actually require roofs over a certain square footage (especially in targeted watershed areas) to have a green roof. More green roofs could actually add hundreds of thousands of square feet of greenery to the city, cool it down, clean the rivers and create habitats for wildlife – all while looking totally awesome.

DC is presently offering a rebate of as much as $10 per square foot of green roof  installed. That’s a VERY significant savings as DC seems committed to the growth of the industry. So do you have a roof that’s ready to go green? Call ecospaces now for a free quote. We’ll work with you to install the perfect green roof and help you get the maximum rebate – all while doing our share to keep DC beautiful.

If you are interested in a Green Roof in the DC, MA or VA area, contact ecospaces at 202.681.3402 for a free quote.