Australia's National Retrofit Insulation Provider

Should You Remove Old Insulation or Top It Up?

New insulation can sometimes go over the old when the existing layer is clean, dry, evenly spread and free of droppings. When it is damp, mouldy, collapsed, full of droppings or nesting, or old loose-fill that has broken down into dust, it should be removed first, because new insulation should never go onto a dirty, dusty ceiling. If there is any chance of asbestos, nothing is disturbed until a licensed assessor has checked it.

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Tile Roof Retrofit

Extraction & Batts

1. Old blown-in removal via vacuum
2. Earthwool® batts install
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Signs your old insulation should come out

  • Mould or water stains from moisture build-up.
  • A heavy build-up of dust in the roof space.
  • Rats, mice or possums nesting in it, or droppings through it.
  • Ceilings cracking or sagging because moisture is held in the insulation.
  • Old materials past their useful life, such as cellulose loose-fill made from newspaper, sheep's wool from the 1940s to 1960s, or early fibreglass batts that are breaking down.

When a top-up can work

If the existing batts are dry, clean, still in place and simply too thin, adding new batts can lift the R-value without the cost of removal. We check this at the free assessment and tell you which option suits the roof.

What removal adds to the cost

Old insulation removal typically costs $15–$30 per m² of ceiling on top of the new batts. For a smaller three-bedroom home with about 120 m² of ceiling, removal adds roughly $1,800–$3,600. The cost guide has worked examples for full jobs.

Asbestos comes first

Some homes built before 1990 have asbestos in or near the roof space, including loose-fill asbestos in some NSW homes. Insulation Extract does not handle or remove asbestos. If it is suspected, work stops until a licensed assessor has checked the roof.

Room with a collapsed ceiling and fallen old insulation
Room with a collapsed ceiling and fallen old insulation
Before and after comparison of a roof space cleared of old insulation
Before and after comparison of a roof space cleared of old insulation

Frequently Asked Questions

Can you put new insulation over old insulation?

Sometimes. If the old insulation is clean, dry, evenly spread and free of droppings, new batts can go over it. If it is damp, mouldy, collapsed or contaminated, it should come out first.

How do I know if my insulation needs replacing?

Look for mould or water stains, heavy dust, droppings or nesting, sagging ceilings, or old loose-fill that has turned to powder. A free assessment includes a check of what is in your roof.

Is it worth removing old insulation?

Usually, when it is contaminated or broken down. Removal typically costs $15–$30 per m² and leaves a clean ceiling, so the new insulation can reach its rated R-value.

What if my old insulation contains asbestos?

We stop and do not disturb it. A licensed asbestos assessor needs to check and, if needed, a licensed removalist deals with it before any insulation work continues.

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