Insulation, Radiant and Vapor Barriers - crawlspace insulation

Question regarding the insulation. I’ve got a crawlspace beneath my porch that I am remodeling. I’m planning on converting the 3 season porch to 4 season and want to insulate the works, however, the area beneath the porch is bare soil. Here is what I’m considering: foam around exterior of porch foundation, foam on top of soil, cover with thin layer of concrete (2-3”). I would also insulate the floor joists with fiberglass. Then insulate the walls, ceiling, etc. move a radiator/baseboard out to porch for heat, etc. Any feedback appreciated.
-Pat
ps-also cross-posted on masonry board

First question is how much height is there under this porch? If you crawl under it, how far is it from the dirt to the bottom of the joists, at the closest spot? Are there any beams supporting these joists? If so, how far from the dirt to the bottom of the beams?

Next, I don't uderstand the logic of putting foam on the dirt and then pouring concrete over it. Foam will not be a good base for the concrete. It will very possibly cause it to crack prematurely. And why concrete at all? Why not just lay down a 6 mil vapor barrier directly on the dirt.

Foam around the outside foundation. What are you going to cover that with?

And how much ventilation will you be providing for this crawl space?

UPDATE:
Definitely going to scrap the concrete idea. Not worth it. Going to go with the 6-8mil poly.

The foam is going on the INSIDE perimeter of the foundation

I ripped the flooring off today, joists were inadequate (2X6 24" OC) running 20' across. Needless to say, lots of bounce. I acquired 4, 21' engineered floor trusses which are rated at 24" OC. since the porch is 7'X20', I'll run those 4 trusses, build up the rim joists and deck it with t&g osb or plywood.

Height under what was the floor is about 3'.

there is currently no ventilation, less the crack between the siding and the block. will probably put a small screened vent in

thanks for the feedback lefty

"... scrap the concrete..." Good idea!

I misunderstood what you meant when you said the foam would be "around exterior of porch foundation".

Good call on the joists.

Cut a couple of 6" X 16" screened vents in the rim joist on opposite sides of the floor (4 total), and you'll be fine.

Sounds like you've got it under control.

I own a duplex with about 3' crawl spaces and went to power ventilation. Bought The vent fan and humidistat controls from a local company that ordered them from FIELD CONTROLS (252)-522-3031 http://fieldcontrols.com

Purchased the self-closing/opening foundation vents from Lowes.

The 6 mil plastic is a good idea (I did that) Make sure to overlap the joints at least 6" and use duct tape to secure. Use bricks at the outer edges to hold down the plastic...no 2X4's....don't want to entice the termites.

Foam wall board on the inside of the cinder block walls works but really isn't worth the trouble unless you are in dire need of insulating for warmth...better off spending the money on fiberglas batts for the flooring. I installed r-19 unfaced. Not THAT was real fun!