I have a old house (1870) and one of its additions is a enclosed porch. The foundation extends the existing basement so I can walk around underneath it (maybe 7ft high). The room is 8X16 and began life as a uninsulated screened in porch. I have run heat into the room but it is cold due to lack of insulation. I have insulated the walls but not the ceiling or the floors. So here are my questions;
1. Should I insulate the floors from underneath with spray foam since it won't need a vapor barrier and it has high r-value
2. If I blow in insulation into the ceiling do I need to add vents to the soffets and the roof itself
Foam underneath is great, but the slab will still be cool or cold to your feet. If that is not an issue, fine. Otherwise, fir out and insulate inside, but you'll lose height, of course. The lid should always be ventilated; check w/ local building inspectors, etc, about whether or not you need a vapor barrier in your area, too.