Mike wrote:
Hi all,
I was cold called by someone trying to get me interested in spraying
foam called "lapolla" onto the underside my roof. I declined.
Anyone have any expreience or expert knowledge of this process?
- Mike

Run away, don't walk.

As well as what's already mentioned, it's very very expensive to remove -
you essentially need a new roof.

Plus the chemicals are mixed on site, and if they do the mixing wrong you
can end up with toxic offgassing. Did I mention that faulty foam is
near impossible to remove?

https://www.bbc.co.uk/programmes/m000v2wr
was mentioned here recently.

https://foursevenfive.com/blog/foam-fails/
has lots on bad foam - it's a big problem in the US where it's more popular.

If you want to install foam, install foam panels like Celotex - easy to
remove, and made in a factory where you know it's been done right.

Theo