Most people already know the benefits of thermal insulation, but what about the environmental impacts of the actual insulation material, or how a building’s structure affects insulation performance?
Most of the environmental benefits of insulation come from the improved energy efficiency of a building and its operational costs. However, there are several additional key aspects that determine the overall environmental benefits of a thermal insulation product by itself.
For example, the environmental burden caused by the manufacture and disposal of thermal insulation materials can be significant if the raw materials are sourced using environmentally damaging processes, are manufactured using ozone depleting substances, or if waste products can only be disposed of in landfill facilities. Correct handling and installation of the product is also a critical factor since the thermal performance of an insulation product can be reduced by 50 per cent even if small (five per cent) gaps result from poor installation.
However, choosing the right insulation materials and installing them correctly will mean reaping the energy-efficient and environmental benefits for years to come.
Glasswool is cost-effective, naturally fire retardant, and can be made from recycled materials. It can be itchy, but simply wearing the right protective gear during installation means there is little chance of coming into contact with the material. Once it’s been installed, there is even less exposure.
Other synthetic materials, such as polyester, can also contain recycled content, but require the application of fire retardant and moisture-resistant chemicals. “Natural” materials, such as wool, will most likely need the same fire-retardant and moisture-resistant chemicals applied to them. They are also more likely to “settle” over time compared to other materials, reducing the air gaps inside the material and reducing their effectiveness.
The biggest factor influencing the effectiveness of insulation is the building design and construction. It’s important to prevent air leakage to stop warm air from escaping during the colder months – sometimes up to 25 per cent of heat loss can be attributed to this. Australian buildings are more ‘leaky’ compared to their North American or European counterparts, allowing an estimated two to four times as much air to escape.
Some of the most common places where air leaks can occur include exterior corners, outdoor water taps, where siding and chimneys meet, electrical outlets, door and window frames, electrical and gas service entrances, weather stripping around doors, fireplace dampers, attic access hutches, air conditioners mounted in walls or windows, TV and phone lines, vents and fans, and where dryer vents pass through walls. Installing a wall wrap (and sealing it with tape) in a new build can help to combat some of these air leakage issues.
Cuts in the ceiling, such as for recessed down lights or home theatre speakers, cause two problems affecting thermal performance of a building. Inadequate sealing (and therefore air infiltration) due to the type of down light fitting and installation allows air and heat to escape, and there is a loss of ceiling insulation value where the insulation must be kept away from the lights for a certain distance to reduce fire risk.
“You can avoid these problems by using surface-mounted lights, or task focussed free standing lamps,” says Dr Shaila Divakarla, GECA’s Standards and Technical Manager and a registered architect. “These often look much nicer too.”
Bathroom exhaust fans should have self-closing dampers that close when not in use to help seal off the space, and it’s also best to make sure kitchen rangehoods are externally ducted and don’t funnel straight up into the ceiling cavity.
From a whole building envelope perspective, insulation in the walls, ceiling and roof needs to be considered in conjunction with windows as well.
“So make sure your windows are up to scratch,” suggests Divakarla. “They need to have some kind of performance glazing – double glazing is good for colder climates, but other performance glazing may be more appropriate in warmer places.”
Compression is another issue to look out for.
“Where you have physical compression of the insulation material, such as at the edges of a typical pitched roof, or in raked ceilings with an insufficient gap between the ceiling and roof, it reduces the air gaps in the materials and therefore reduces the effectiveness of the insulation,” says Divakarla.
Damp or wet insulation also has reduced performance as water or water vapour fills the air gaps in the insulation, thereby reducing the resistance of the insulation.
Anything that reduces the effectiveness of insulation, such as compression, air leakage or dampness, can have an adverse effect on the R value of any installed material – for example, an R4 insulation might in real life function as low as an R2 insulation.
Choosing the best insulation involves a lot more than simply choosing the right R value. It’s important to consider the material itself (and its associated environmental impacts), the design of the building, and whether the material has been properly installed. However, correctly-installed insulation results in significant energy efficiency gains. It pays to get it right.