How to choose the right insulation for your home and the environment

Image of How to choose the right insulation for your home and the environment

Most people are aware of the benefits of building insulation: it’s the energy-efficient way to keep your home at a comfortable temperature all year round. Insulation keeps the heat outside during summer, and helps to trap valuable warmth indoors when it’s freezing outside, lessening the need for additional heating or cooling. Most of the heat transfer occurs through the roof and ceiling system, which is why ceilings are the most commonly insulated areas in a house, but windows and walls are also responsible for significant heat losses or gains.

The main environmental attributes 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 waste product 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% even if small (5%) 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.

Insulation has health benefits, too. Research conducted in New Zealand involving 1,400 homes and nearly 5,000 individuals found that people living in insulated homes that were warmer and drier reported a significant improvement in the health of adults and children compared to people living in uninsulated homes (Housing and Health Research Program, Wellington School of Medicine, University of Otago). Adults and children living in insulated homes reported fewer visits to their GP and were admitted less often to hospital for respiratory conditions. Adults were also significantly less likely to report sick days off work, and children were less likely to have days off school.

So how can you get the most out of your insulation?

Understanding R- Values and building codes

As a general rule, a higher R-value means better insulation performance. This doesn’t mean you should deck out your home using only the insulation materials with the highest R-value you can find, however. Material R-values describe the thermal resistance of the insulation material itself, while a Total R-value takes into account all the floors, windows, doors, walls, roofs, cladding types, and so on, working together as a system (also referred to as the ‘building fabric). The Building Code of Australia (BCA) states that the required total R-values for the building fabric will vary depending on the climate zone and the building site’s height above the Australia Height Datum.

Making the most of your insulation

The effectiveness of insulation depends on the building design and construction. Preventing draughts and air leakage is vital to stop warm air from escaping during winter – sometimes up to 25% of heat loss from a home can be attributed to this. It is estimated that Australian buildings leak two to four times as much air as North American or European buildings.

According to Fletcher Insulation, 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. Fletcher Insulation’s Talis Krumins recommends installing a wall wrap (and sealing it with tape) in a new build 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: the 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 considered in conjuction with windows as well.  “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.

Recommended materials

Glasswool is cost-effective, naturally fire retardant, and can be made from recycled materials (Fletcher Insulation glasswool products, for instance, are produced from 80% recycled glass content). Glasswool can sometimes be itchy, but as long as you wear protective gear when installing, there is little opportunity for direct exposure – and once 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. And “natural” materials, such as wool, aren’t always best - they typically need these 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 as insulation.

Making decisions about your insulation

Not sure where to start? Fletcher Insulation’s website contains a wealth of information, or check out their app, FletcherSpec™ Pro. The app is designed to overcome many traditional issues Architects and Builders face when specifying insulation and helps guide users through the entire insulation specification process. 

FletcherSpec™ Pro helps to bring together all of the tasks associated with typical System R-value calculations – such as determining the relevant climate zone, referencing applicable energy efficiency requirements, considering solar absorption values of roof cladding and selecting the correct insulation products for the application – into one place. This drastically minimises the need to manually cross reference inconsistent or out-dated handbooks, and technical data sheets. Instead, users simply answer a series of targeted questions which the app uses to determine relevant energy efficiency requirements as outlined in the National Construction Code Deemed to Satisfy provisions. The app then progresses to calculate the Total R-value of the design based on the inputs entered by the user, saving time and streamlining the insulation specification process.

The app provides a multi-faceted, smarter approach to selecting suitable insulation. This overcomes the issues faced when trying to identify an appropriate product that will satisfy building code requirements.