Do not spray foam over suspected asbestos or vermiculite until it's been tested and, if needed, professionally handled. Foaming over asbestos-containing material can trap or disturb fibres, and it turns a manageable problem into a buried one. The safe path is test first, abate if required, then insulate.
Why it's risky
Older homes and attics can contain asbestos (including vermiculite attic fill). Spray foam is applied under pressure and bonds permanently - exactly what you don't want happening over material that may need to be assessed or removed. Once foamed over, dealing with it later means removing the foam too.
The safe sequence
- Test suspect materials before any insulation work.
- Abate through a qualified process if the test is positive.
- Then insulate the clean, safe substrate.
A responsible installer will stop and recommend testing if they suspect asbestos - not spray over it. See when not to use spray foam. Get a quote.