What types of insulation are available for your roof?

One of the simplest ways of keeping your home comfortable and reducing your energy use is to install insulation in your roof. It can also control the level of noise in your home and provide peace and quiet. But with several different types of insulation available, how do you know which kind to choose?

There are two main types of insulation, with different benefits to each. 'Batts' are pre-cut pieces of insulation that come in standard sizes, while 'blown-in' insulation is exactly as it sounds: it is a loose material that is blown or 'sprayed' into the roof space, using a hose-like device.

According to Peter from Cosywrap, the choice between the two types of insulation will depend on your home's design. "Homes with low roofs, difficult access or air-conditioning ducts are better off using blown-in insulation, because it gets into all the nooks and crannies and there are no gaps," he says. "Old homes with big, high roof spaces can have batts installed if the ceiling joist is standard width, but it depends on the space, as the insulation either fits or it doesn't. 

Roof batts

Batts come in varieties such as glass wool, rock wool and polyester, which all provide different benefits. So, what is the best roof insulation choice? "Rock wool is both acoustic and thermal insulation; it's the best thermal acoustic product," says Peter. "Polyester is the next best for acoustics and thermal [performance] and glass wool is equal for thermal but doesn't have the acoustic benefits." 

Blown-in insulation

There are two types of insulation in the "blown-in" category - cellulose/recycled-paper insulation and rock wool. Rock wool blown-in insulation is made of the same material as the rock wool batts, and has the same benefits. The cellulose/recycled-paper type is made from paper and contains boracic acid, which acts as a fire retardant and insect repellent.

Another factor that may affect your choice of insulation in your roof is whether there is already insulation present. "If there's old insulation there, blown-in is the way to go, as it fits in between the old batts, whereas putting new batts on top of old ones doesn't work very well," says Peter.

Preparing to insulate

Regardless of the type of insulation you choose, it's important to remember that if you're re-insulating an existing home and have removed the old batts entirely, you need to vacuum out the roof space once you've removed them. Similarly, if you're renovating a house and dropping the ceilings, you should vacuum all the loose material out for the best roof insulation result.

While it's possible to install roofing insulation yourself, Peter says it pays to get a professional to do the job. "Every 1% gap in the insulation means you lose 5% of the efficiency," he says. "So if you don't install it correctly, you'll lose a lot of the benefit."