First the off-gassing. It emits a lot of harmful compounds as it cures and I understand the emissions to go on for a long time. So if you mind about air quality it wouldn't be my choice.
Second is the potential for damp to build up in the building fabric. The foam is airtight so make sure the ventilation is right on both sides of it.
A bonus third is the pain of removing it when you need to do building repairs. With board or batts you can lift them out; with spray foam you have to cut then scrape off.
First the off-gassing. It emits a lot of harmful compounds as it cures and I understand the emissions to go on for a long time. So if you mind about air quality it wouldn't be my choice.
Second is the potential for damp to build up in the building fabric. The foam is airtight so make sure the ventilation is right on both sides of it.
A bonus third is the pain of removing it when you need to do building repairs. With board or batts you can lift them out; with spray foam you have to cut then scrape off.