Insulating a crawl space in hot/humid Miami
I have searched the web for what seems like days about crawlspace insulation. I find conflicting information and really no information on my specific climate factors.
1950's house built on above grade crawlspace. Original crawl was vented on all 4 sides. 2 additions added in the 1980's are slab & are on the South, West & North sides of the house. That leaves me with 2 original vents on the East side (about 8 ft apart), 1 on the South & 1 on the West. There is no access from inside the house. The home had original oak floors that had significant termite damage & some tile on top. I removed all bad wood, replaced with plywood, layed tarpaper & went over with walnut. The crawlspace has no insulation. I did put down 8mm plastic sheets on crawlspace floor but have not made it airtight yet (not taped or attached to walls). I did it to tell if my new plumbing was leaking & also to make the space nicer for my workmen. They are less likely to leave debris behind when the space is clean. The ground is not wet but I can tell from digging that there is some moisture. The only pipes in the space are plumbing. All a/c pipes are in the attic.
During the summer months when the a/c is running I have serious cold air leaking into the crawlspace. When you walk past the 2 East facing vents it feels like I have an a/c duct right there. The air coming from those vents is freezing cold & can be felt 3 feet from the vent hole. During the winter I feel nothing when I walk by the vents. So, my assumption is that when I have a/c running I have ALOT of cold air settling into the crawlspace & then blasting out of the side of my house. So my goal is to keep the cold air IN my house.
Possible solution based on research:
Closed cell spray (for potential flooding issues) between floor joists. Only need spray for air leakage and not R value as crawl space is cool.My gut tells me to keep the crawlspace venitlated.
Concerns: Do I keep an airspace (1-2")between sub floor & sprayfoam like they recommend with batt insulation? Should I make the plastic ground cover airtight?