Why your green building needs a green roof

After exploring green roof semantics, and divulging how to build your own green roof in my last post, here are some reasons to invest in this popular green building technology.

1. A green roof makes for a cooler green building. And I do mean cooler in both ways - lower temperatures and trendier looks … well, at least as far as your eco-minded friends are concerned. A green roof adds thermal mass to your green building, acting like a really great insulating layer. In general, better insulation and additional thermal mass help to stabilize the interior temperature, reducing your cooling loads in the summer and your heating loads in the winter, and thereby lowering your energy bill. The added insulation of a green roof also acts as sound proofing, which, while it might not translate into direct energy savings, certainly makes your building more livable.

The green roof cooling effect can even work on a large scale - a high enough concentration of green roofs in an urban area can reduce the "heat island effect." As urban areas are developed, land surface is replaced by building and paving materials, many of which effectively retain heat, collectively contributing to urban "heat islands." Green roofs can, for obvious reasons, reverse this phenomenon.

If you're in the market for an insulating roof system for your green building, a green roof is an especially good choice because, unlike a simple polystyrene insulated roof, it provides other environmental benefits such as reducing CO2 impact, filtering pollutants out of the air, and creating vegetative habitats in urban environments; [the buzz word that goes along with this last concept is "urban wilderness."

2. A green roof works as a storm water management system. Not only does a green roof set you up to utilize otherwise unused rainwater [i.e. by watering the plants on your roof] but it also helps to reduce the volume of storm water runoff at peak times by slowing down the flow of water that would otherwise drain off immediately. Additionally, the vegetation can help to filter pollutants and heavy metals out of rainwater, preventing these unwanted materials from entering your storm drain system.

3. A green roof could create additional agricultural space for food and/or biofuel production. There are all sorts of pragmatic issues with this third point, but let's just go with it for the moment.

4. A green roof advertises the fact that your building is a green building. Now, that's not to say that a green roof doth a green building make, but with a green roof, even if yours isn't really a green building, at least it'll look like one!

I know … I know … when it comes to green buildings we're not supposed to talk about this kind of benefit - the kind that deals with perception and image and marketing. Instead, the focus is always placed on energy performance, pragmatism, and functionality. That's how we distinguish ourselves from those who are merely greenwashing. However, the truth of the matter is that architecture isn't just about energy performance, pragmatism, and functionality; it's also about perception and image and even marketing. If you ask me, if we want to take green building to the next level, to begin to think about what green architecture means, we have to think not only about how it works but also what it looks like. We should embrace the image question, not shy away from it.