It’s very green and ecologically responsible and etc. etc. of us to put in the living roof, but we originally just wanted it because it looks nice.
Because our roof is visible (due to the slope of the property) the folks in the main house and the neighbours are looking at it whenever they look at the laneway house. And because we have flat roof not just on the upper storey but also on the top of the garage and some of the lower storey, we just wanted something nice for them to look at. The roof of the garage is right outside our kitchen window, and it’s much more pleasant to look at a garden than a heli-pad black slab.
Our roof is an extensive green roof, a carpet of sedums and other low-growing plants. An extensive green roof would support larger plants, even trees.
But it turns out there are lots of other very good reasons to install a living roof of either kind. According to the Green Roofs for Healthy Cities site, living roofs offer benefits to more people than the home owners.
1. Cleaner water. Living roofs clean storm water. Here in Vancouver we can have real downpours. The water runs off hard surfaces like roads, sidewalks, and yes, roofs, and enters the storm sewer system. All at once. That can overwhelm the system. But living roofs absorb and retain the water, delaying its entry into the storm sewer and easing the pressure on the system. Plus the roofs filter the water, and through evaporation, lessen the of water they deliver to the system.
2. Cooler cities. You may have heard about the “urban heat island effect“. This is a problem for big cities where the structures absorb heat during the day and retain it far longer into the evenings than soft, natural surfaces. According to the EPA,
The annual mean air temperature of a city with 1 million people or more can be 1.8–5.4°F (1–3°C) warmer than its surroundings.3 On a clear, calm night, however, the temperature difference can be as much as 22°F (12°C).3
The living roofs keep cooler during the day due to the evaporation that goes on, but they also cool off much faster than hard, black roofs once the sun is down.
3. Cleaner air. Plants clean the air of pollution and particulates. So living roofs can reduce smog.
For individual home owners:
1. Energy efficiency. The living roof acts as an insulator during the winter, keeping the home warmer. Plus in the summer, it keeps the home cooler because the plants provide an insulating layer PLUS the evaporation of water through the plants lowers the temperature. You may have set a sprinkler on your roof during the super hot weather to cool it off — that works by evaporation and our roof does that all the time naturally.
2. Fire retardation. If a building near by catches fire and the sparks land on our roof, they will just go out. It would be like trying to light a lawn on fire.
3. Noise reduction. According to Green Roofs,
An extensive green roof can reduce sound from outside by 40 decibels, while an intensive one can reduce sound by 46-50 decibels
4. Increased durability. The plants protect the membrane below them from the destructive rays of the sun. A living roof can last at least two times longer than a plain membrane roof. And that keeps membrane and sealant out of the landfills.
There’s some maintenance to be done on the roof — weeding! We’ll also be putting on a little fertilizer. Thanks to N.A.T.S. Nursery for their help.
Visit N.A.T.S. Nursery at their website for more information.`