When and how to update your insulation

Insulation is one of the best ways to lower your energy use, but can become less effective over time. So when do you need to replace or top up your insulation?

Your Home
5 min read
Insulation is one of the best investments you can make to reduce your energy use, but water, dirt, dust and compression of the material over many years will reduce its effectiveness over time.

As one of the best ways to save energy in the home, insulation creates a barrier that keeps the heat in during winter and out during summer – meaning that households can reduce their heating or air-conditioning use, and save energy. But insulation needs to be maintained to ensure it stays effective.

When should I replace my insulation?

As a general rule, insulation should be replaced or retrofitted every 15 to 20 years. However, it may need replacing or retrofitting sooner depending on the type of insulation installed, the R rating of the original insulation, compression and movement over time, and whether any damage has occurred.

Look for these signs that your insulation might need attention:

  • Fluctuating indoor temperature
  • Higher energy use than usual
  • Pest infestation (ceilings are the most common area for possible intrusion of rats, mice or possums)

The first step is to check if there is any existing insulation. If so, is it still thick, or has there been any damage or compression? If this isn’t something you want to do yourself, get an expert in.

Think about ‘R-value’

One of the benefits of replacing or adding insulation is reassessing whether the existing insulation’s ‘R-value’ suits.

The R-value reflects a material’s heat resistance – the higher the R-value, the higher the resistance. Many homes built before the 1990s do not have any insulation (around 13 million homes) and, of those that do, many don’t have optimal insulation (around 2.1 million).

Replacing your insulation gives you a chance to achieve a higher R-value – and more insulation should mean lower energy use within the home, as well as increased property value. Speaking to an expert will help you determine the best options because some roof spaces are more difficult and expensive to retrofit than others (such as flat roofs) and different types of insulation suit different climates.

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Types of insulation

There are several types of insulation to consider. They suit different climates as well as houses.

Reflective insulation

  • Double-sided and reflects heat, either away from the property (during summer) or towards the property (during winter).
  • Best suited to walls and roofs.
  • Works best when paired with sealed air gaps.
  • Sometimes includes metal, and should only be installed by an expert.

Batt insulation and insulation blankets

  • A popular and easy to install option that’s suitable for walls, roofs and floors.
  • Can be fibreglass, rockwall, paper-based and polystyrene-based.
  • Comes in blankets, boards and batts.
  • Creates a physical barrier, directing heat depending on the season.
  • Fibreglass products can be itchy to install and compresses easily (i.e. loses insulating properties). It retains moisture and can harbour mould.

Loose fill and blown in insulation

  • Lightweight material.
  • Blown in with a special machine, ensures that there are no cold spots in hard to reach nooks and crannies in the attic.

Spray foam insulation

  • Generally has a higher R value than batt insulation.
  • Forms an air barrier to stop thermal transfer.
  • Can contain petroleum or plant-based products, and will release chemicals and VOCs (volatile organic compound) during application and curing.
  • Less likely to sag or move out of place.

Other considerations

Structural integrated panels are very effective, but are often more expensive. They come in large sheets, and are mostly used in renovations and new builds. While R-value is a great way to figure out which insulation material to use, there are other things to consider, including whether you want sound-proofing, environmental impact (such as using natural materials rather than manufactured materials) and what existing shade your property has.
It’s important to check the product you select is compliant with Australian standards.

When you engage with a professional installer, make sure you conduct a background check of the company you’re dealing with and read online reviews.

Finally, take your time to choose the right insulation product – shop around and do your research to ensure your select the right product for your house and climate.

A well-insulated property can still struggle to achieve maximum energy saving without sufficient shading, so an insulation assessment is a good time to look at whether nearby trees are providing adequate shade to the house – deciduous trees and vines are ideal.

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