How Can Green Roofs Insulate Against Heat And Cold
Green Roofs and Insulation
Installing a green roof can save you money both at home and in your business by cutting energy costs
How a Green Roof Can Help You Save
During the winter months it is possible to gain up to an extra 25% insulation in dry conditions by installing a green roof. It can also raise the outside temperature of the roof on average by 4.5°C when the weather is cold; and reduce heat loss due to wind by up to 50% compared to a bare roof. By keeping the roof of your property covered in this way less heat is lost from the inside meaning you won’t have to spend as much money to stay warm.
In the summertime a green roof has the ability to keep properties cooler than bare roofs by average of 15°C. It is not uncommon for homes and businesses to spend more on air conditioning in a year than heating. Given the amount the temperature outside of a building can affect the inside, installing a green roof covering can reduce the need for artificial cooling systems by doing it naturally for you.
The level of insulation a living roof can provide though depends on many factors. The moisture level of a green roof can greatly determine how effective it is as an insulator. As moisture levels can vary enormously depending local climatic factors, the thermal performance of the roof will vary too. It is for this reason that green roofs are not given a U-Value.
The type of green roof you choose will also influence its thermal performance. Generally, the deeper the layer of growing medium, the better the roof is at insulating – but the weight of an intensive or semi-intensive green roof can put a lot of strain on a building.
On the other hand extensive systems, such as Enviromat Sedum Matting, are typically more lightweight so may not provide quite as much insulation, but they are cheaper to install and easier to retro-fit onto garden buildings, porches or garages.
The Urban Heat Island Effect
Installing a living green roof is a simple yet effective way to combat the urban heat island effect. This is the term used to describe the temperature difference between rural and built up areas. The difference is caused by lots of buildings reflecting and radiating heat from the sun meaning that densely populated areas can become significantly hotter than rural areas. Green roofs fight the urban heat island effect by:
- Absorbing solar heat, as opposed to reflecting it
- Releasing moisture cooling surrounding atmospheres
The process of plants releasing moisture back into the atmosphere is known as Evapotranspiration. This is a very important part of the water cycle and essential for avoiding periods of drought.