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What impacts the R-value performance of insulation?

What impacts the R-value performance of insulation?

Every insulation product you buy in Australia has an R-value, which tells you how resistant it is to heat transfer, and therefore, how effective it will be. A higher R-value means better insulation for your home, but even if you install insulation with the highest rating, it’s important to remember that its performance can be affected over time by several factors.


As with most things, insulation must be installed correctly in order to function properly. If done poorly, the flaws can have a significant impact on the amount of heat retained or lost, and on your energy costs. Even the smallest gaps around edges or between materials can dramatically reduce R-value performance, so make sure you choose an experienced and reputable insulation professional.


Forcing extra insulation material into a space designed to hold less won’t result in better insulation; in fact, it will have the opposite effect. Compressed insulation won’t have the full R-value the product is supposed to have, which is why it’s so important that the thickness of the insulation is exactly the right size, and not compressed.


For absorbent insulation products like conventional glasswool batts or cellulose, moisture can dramatically affect performance.  To continue doing its job, thes types of insulation materials need to stay dry, and that means controling the moisture around your home. Making sure you have proper ventilation in wet areas like your bathroom, kitchen and laundry; fixing roof leaks; keeping your gutters clean; and providing good drainage away from your house will all help to minimise moisture.

Air leaks are another factor that should be addressed to prevent moisture retention. When air enters walls and roof space through gaps around electrical outlets, air ducts and plumbing connections, it carries a lot of moisture, so these areas should be sealed properly.


Reflective insulation materials work by reflecting radiant heat away from its highly reflective foil surfaces.  Dust accumulation can affect the reflectivity of these surfaces and therefore impact performance.  The good news is that the Australian insulation standard (AS/NZS 4859.1) already requires R-value calculations for reflective foil insulation products to take into account a reduced performance factor due to dust cover.  So the advertised R-values you see from reputable insulation suppliers will already take this into account and will accurately represent their installed performance.

Keep these considerations in mind when you’re building or renovating your home, or make sure there’s nothing in your current home that could reduce the R-value of your insulation. Your choice of insulation material, correct installation and the right conditions will go a long way in keeping down your energy costs and prolonging the life of your heating and cooling appliances.

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Kingspan Insulation is a market leading manufacturer of innovative ultra-thin flexible insulation products and super high performance rigid insulation products for building fabric and building services applications.