Two kinds of spray foam are used under roofs, and they behave differently.
Open-cell
Soft, spongy and light. It lets some moisture pass through but can still hold it against timber.
Closed-cell
Dense and rigid. It sticks hard to tiles and timber, which makes removal slower, and it can trap moisture behind it.
Why we record it
The type affects how the report is read and how removal is planned, so every assessment notes it.
Related: FAQ