Should I Spray Foam Under My Acrylic Tub Can I Put The Spray Insulation That Comes In The Can (great Stuff) Under My Vinyl Siding On The Very Bottom?

Can I put the spray insulation that comes in the can (great stuff) under my vinyl siding on the very bottom? - should i spray foam under my acrylic tub

I like to avoid spraying foam on the bottom of the food, where outside.There space-based monitoring of the flow should be sufficient space to avoid the rest of the coating has a circulation of air, to let moisture. Right?