Healthy insulation: wood fibre, polyester or glasswool?

Insulation sits inside the walls and roof for the life of the house, and some of it ends up in the air you breathe. Here's how the three healthier options compare.

Wood fibre

STEICO wood fibre batts are dense, vapour open and take up and release moisture, which helps a wall manage humidity. They're pleasant to handle and Passive House certified.

They cost the most, only one thickness is held in stock, and there's no Queensland depot, so plan early and budget for freight.

Polyester

Autex GreenStuf is thermally bonded polyester with a lot of recycled content and no glues. It doesn't itch or shed irritating fibres, which suits roof spaces over living areas.

It's plastic, and it doesn't buffer moisture the way wood fibre does.

Formaldehyde-free glasswool

Knauf Earthwool uses a plant-based binder instead of formaldehyde and is Declare Red List Free. It's the cheapest and easiest to get, which makes it the realistic upgrade on a tight budget.

It's still glass fibre, so the installer needs a mask and the ceiling needs to be sealed.

Installation beats brand

Gaps, squashed batts and missing pieces around downlights can wipe out a big chunk of the rated R-value. Walk the job before the plasterboard goes on.

Insulation doesn't stop air. Pair it with an airtight layer and taped joins, or warm, moist air will move straight through it.