Saving Money by Going Green - Green roofs Can Cut Air Conditioning Use by 40%

If you cannot keep up with electricity bills this summer because air-conditioners are constantly switched on, green roofs could be your solution.

It is estimated that green roofs can cut air conditioning use by as much as 40 per cent and a study by the University of Malta, which ends this week, has shown that this alternative could lower the roof temperature by half.

Led by landscape architect Antoine Gatt, the LifeMedGreenRoof Project has seen the creation of an experimental green roof at the Faculty for the Built Environment.

Roof slab and membrane suffer damage due to changes in temperature over a 24-hour period. Studies at the faculty have shown that the temperature of the membrane can vary by as much as 30˚C over 24 hours in mid-August.

On a regular roof, solar energy is absorbed by the roof slab and damp proof membrane. The temperature of the damp proof membrane can reach 55˚C during the day and plummets to 25˚C by night.

The energy absorbed by the roof slab is reflected into underlying rooms making them uncomfortable to live in and necessitating the use of air conditioning. The temperature of the membrane beneath a green roof remains stable at 27˚C.

“The fact that the temperature remains constant means that the slabs and the membrane do not expand. The green roof also protects the membrane from the natural elements, translating into less maintenance and less waste as you would not have to replace the membrane as often,” Mr Gatt said.

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