In my part of SoCal, there are only about 12" ave annual rainfall, 275 sunny days to 35 with any measurable precipitation, and ave annual humidity of just 70%. So if I keep the crawl space vents sealed from the outside during the winter "rainy" season, how much moisture can really get to the insulation in the crawl space, barring a disaster?
I ask because the cost of professionally installed dense-pack dry cellulose in the crawl space under my home is greater than I can afford if I want to complete other needed repairs and improvements. My walls will be professionally insulated with dense-pack cellulose. But I need to DIY the crawlspace. I therefore am stuck between a choice of the R-13 fiberglass batts with facing as a vapor barrier (cheap but not green and not nice to work with) or the R-19 cotton batts (which are pricey and need a separate vapor barrier installed, I suppose). If the cotton batts are so bad in terms of water attraction that they will fail, then I will have to go with fiberglass batts. Are they really that bad in a climate like mine?
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