Cotton insulation?

[S-F]

In So Cal (FWIW my frame of reference is the several months I have spent in San Diego) you don't really have to think about insulation the way we do in northern climates. I myself would never follow the recommendations I gave you for my own house. I'd condition the crawl space. It would be a nightmare, as you have noted, and would be much more costly. I'm assuming that cooling is more important there than heating. Air seal the attic to the hilt and put as much cellulose up there as you can fit. Then your next biggest culprit will be glazing. In fact, windows probably contribute more to your heat gain than your attic does. Maybe some really good external shades are going to make more of a difference than the attic insulation...

[Eco1]

For those who have inquired about cotton insulation.
Having worked in and around the insulation industry for almost 30 yrs
I am a huge fan of Cotton Insulation.
Not only is it healthier for people and planet it is slightly higher in R-value than FG and much better for sound control.

ECO Building Resource

[S-F]

Originally Posted by Eco1

For those who have inquired about cotton insulation.
Having worked in and around the insulation industry for almost 30 yrs
I am a huge fan of Cotton Insulation.
Not only is it healthier for people and planet it is slightly higher in R-value than FG and much better for sound control.

ECO Building Resource

I am unsure of it's R value. Last I heard from sources I consider reliable the R value was lower. R Value charts are all over the place and I personally don't put too much faith in any of them. That being said, it is certainly nicer to work with. Cotton is all I wear next to my skin. It has three big factors playing against it. It's expensive, it comes in Batt form and it has a horrible hygroscopic profile. There is no way I would put it in a crawl space. If I were a building inspector I would not allow it in such an application.

[rhizomatic]

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?

[S-F]

It's not about rain. It's about condensation. There is always moisture in the air. If you're close to the ocean there can be a lot. If you can't wait I would put R 19 fiberglass batts in. Just be careful to install them properly.