Use a vapor barrier to keep your floor above free from condensation caused by the new insulated area.
Easy insulation floor insulation covered back porch.
Insulating the floor is an important step in porch conversion.
If you can crawl under your porch insulate from below by nailing plywood boards to cover any openings.
The job of insulating the floor is easier if there is room to crawl underneath but if there isn t it can still be done.
The problem is probably undersized joists and a lack of air sealing.
We are in the process of building a 4 season porch from the original open porch that came with our 1917 home in ne ohio.
Screw sheets of plywood to the underside of the joists to keep the insulation clean and protect it from wildlife.
The friction between the sides of the batting and the studs will hold the insulation in place.
If it is above grade winter drafts will make the room too cold to use no matter how well the walls and ceiling are insulated.
Roll out the fiberglass insulation sheets between the joists facing side up making sure it is snugly in place.
They are also very susceptible to drafts.
Large foam insulation sheets can be nailed directly against the floor above or held in place by chicken wire or other metal elements with the facing against the underfloor.
Crawl under your porch and install strips of batting between the floor joists the same way this time with the facing side upward.
Make sure that you wear gloves and a mask for protection.
Sometime in the 1940s the previous owners had crudely enclosed this second floor porch with nine simple casement windows that open inward but there is no insulation nor any hvac in the enclosed porch.
A contractor i hired to insulate under my 3 season porch floor has used regular pink insulation r 27 but it has fallen out four times so far now half of it is on the ground.
The insulation should fit snugly to prevent air from getting through.
What we ve done when we ve built a 3 season room is always used 2x12 s for the floor put cleats between joists near the bottom dropped in plywood glued the edges of both the plywood and the cleats to air seal then install the thickest fiberglass insulation possible.
This can be stapled up between the floor joists.