GREEN ROOFS

Our group is known as F.A.M. inc. My name is Dr. Lola Justice and along with my fellow workers, Dr Samantha Hudson and Dr. Wallace Noot, we have been working on building an energy efficient house for the last couple of months. This task required us to come up with ways to cut down on energy use as much as possible. As well as reducing costs this is important if we are to cut down on greenhouse gas emissions and help stop global warming.

We have come up with various strategies to meet our goal. Out of the six strategies that we have used in our house we have chosen the green roof as the most important device for reducing the amount of energy used. We have chosen this particular device because the green roof has been well investigated and it is becoming very popular in various countries.

A green roof is basically a layer of vegetation that grows on a layer of soil on your roof. Beneath the vegetation and the soil there are various other layers. There is a drainage layer to take water away from the roof and a waterproof roof membrane to stop water getting into the building. There is also a root barrier layer that protects the roof membrane from the roots of plants.

The cost of installing a green roof depends on the type of green roof used. There are two types of green roof extensive and intensive. An extensive roof involves simple plants, shallow soil and it is less effective at cutting down on energy transfer however it is cheaper to install. It costs $8-20 dollars per square foot. An intensive green roof involves a variety of different plants that are more visible and have more colour and beauty and this green roof has a deeper soil layer. The cost of installing this type of roof is $15-25 dollars per square foot.

There have been a lot of scientific investigations done to determine the effectiveness of green roofs at cutting down on energy transfer. I would like to tell you about experiments that have been done in Ottawa by Dr Karen Liu working for the National Research Council of Canada.
In her experiments Dr Liu has measured the amount of heat transferred through an extensive green roof and compared that with the amount transferred through a regular roof for each month of the year. During the spring and summer the green roof reduced the amount of heat transferred substantially. The green roof was very helpful for keeping the building cool in summer. She reported that “the average daily energy demand for space conditioning was reduced by 75%”. She found that during the winter when the green roof was frozen and roofs in Ottawa were covered with snow, the green roof did not make as much difference.

Having done this research on green roofs we have discovered that they can cut down on energy use in buildings and therefore reduce greenhouse gas emissions and help stop global warming. As energy costs increase in the future we believe that green roofs will be very useful at cutting costs, especially for cooling in summer. We recommend that city council investigate using a green roof on a municipal building to cut energy use. We appreciate that you have allowed us to come and give our speech today.