Insulation, Radiant and Vapor Barriers - Crawl Space Insulation

My house sits about 18 to 24-inches above grade with concrete foundation at grade. I can get to space below house. I've seen recommendations to apply rigid insulation to perimeter walls between grade and floor structure. However, the perimeter walls have a series of 6 x 12 screened vent openings. Does this mean that another insulation method is required, as I assume I want to retain these vents?

We block all vents in there . You need a 4 or 6 mil poly on the ground over lap it 2' tape the seams up the wall also . A 2 or 3" polystyrene on the wall up to the joist. In the joist space up there on the sill plate put a block of R19 insulation in it all around the home. if you have duct work down there put a register in it .;) ED

Ed,
Do you recommend getting a radon check done once a year since you suggest closing the crawlspace vents, and basically sealing it up? I remember the radon bandwagon being jumped on some years ago (I think the latest one now is mold).

Another question is humidity levels in the crawlspace - what is acceptable? I'm currently running between 45-55% now.

Thanks!
Jeff

NotMrWizard Boy that on radon check Im staying out of. On www dont see a lot about it anymore. I know some say put a pipe in under the poly on the ground and vent it to the out side tape real good where it comes out of the poly and others say ok with that 2' lap seam and tape on the poly. When you have ducts down there we put in 2 heat outlets off the duct and one return. this should get the mold out . But yes mold is the big thing now.

Go to www.aboutsavingheat.com/crawlspace.html

read it, its good dont like the foil back insulation there . ED;)