Can I put new insulation on top of old?
Yes, if the old insulation is dry, clean, even and not contaminated. A top-up laid across the joists brings the total to 270 to 300 mm and keeps the cost down.
When should old insulation be removed?
- It is damp, or has been wet from a roof leak
- It is contaminated by rodent or bird droppings
- It smells, or has smoke or fire damage
- It is badly compressed under old boards
- It is vermiculite loose fill, which must be tested for asbestos before anyone disturbs it
How much does removal add?
Removing and disposing of old insulation adds roughly the same again as laying new insulation in a typical loft. Our guide prices are on the removal page.
Related services
Sources: Energy Saving Trust: roof and loft insulation; Which?: loft insulation costs and savings; LABC: building regulation requirements for loft insulation; GOV.UK: extending the ECO4 end date, government response; GOV.UK: VAT on energy-saving materials (notice 708/6); Property Care Association: spray foam guidance.
