Install or top-up ceiling insulation


Stop heat in its tracks and keep it in your home by installing new ceiling insulation or topping up your existing insulation.

Because hot air rises, more heat is generally lost through the ceiling than anywhere else - typically 35 per cent. Installing effective insulation will reduce both heat loss in winter and heat gain in summer, meaning your home will stay at more comfortable temperatures for longer, and reduce the amount of heating and  cooling required.

Most Tasmanian homes have insufficient and inconsistent ceiling insulation. Fortunately, ceiling insulation is the easiest type to install or top-up. 

How much insulation should I have?

‘R-value’ is a measure of how effective insulation is - the higher the better. The Building Code of Australia (BCA) sets out minimum total R-values required for new homes and extensions. For example, R4.1 for ceilings in Hobart. But this is only a minimum requirement. Homes built to the German Passivhaus Standard usually have in excess of R10.0.

The total R value of your ceiling also includes the building materials (plasterboard, roofing material, etc), which typically adds about R0.3. The remainder needs to be made up with insulation products.

Ceiling insulation batts typically have R values of 3.5 or 4.0. Thicker batts are available, but higher R-values can also be achieved by doubling up thinner batts, with the second layer laid cross-ways to avoid gaps.

Which material?

Fibreglass and polyester batts are often made from recycled content (e.g. bottles), which is great for environmental reasons. The fibreglass material in batts is biosoluble, meaning it is non-hazardous. Good fibreglass batts are bonded with inert polymers made from renewable bio materials. Wool has the appeal of a 'natural' material, however this comes into question with the manufacturing of wool batts requiring cleaning, bonding and treating for resistance to pests (e.g. moths and rodents). On cost, fibreglass wins comfortably.

Problems with downlights

Downlights (ones that are recessed into the ceiling) cause problems for ceiling insulation, especially halogen downlights. The problems are fourfold:

  1. Halogen lights are inefficient, so waste a lot of energy.
  2. Halogens get hot and so, to minimise fire risk, large gaps in insulation are required. This reduces the effectiveness of the insulation.
  3. Downlights of all kinds require a hole in your ceiling, often allowing warm air to escape, especially around gimbals.
  4. The combination of the hole created by light fittings and the heat produced by halogens produces a 'chimney effect' (hot air rises), actively drawing warmth out of your home and into the roof cavity!

So, while you're getting insulation topped up is a really sensible time to get rid of halogen downlights. Fortunately, new LED downlights with an IC-F rating eliminate these problems as they can have insulation place directly over them. This is because they are so efficient they produce very little heat. You still need to be careful about draughts between the light fitting and ceiling, and concerns have also been raised about the lifespan of LEDs being reduced if they are insulated over, but we're yet to see the extent to which that happens.

A DIY Job?

Most types of insulation batts are easy to install yourself if you follow the manufacturer's installation instructions. Do your research, set aside a day and borrow or rent some protective clothing such as a dust mask, goggles and a long-sleeved shirt. For loose fill cellulose fibre insulation, you’ll need to call in the professionals.