I've always wondered why timber framing (and sheathing) isn't sprayed with a borax/boric acid mix prior to sealing it all up with tyvek or whatever.

It's cheap, deters wood-destroying insects, and also acts as a flame retardant.

I know that there's fire retardant paint, and that you can buy pressure treated fire retardant wood to build with, but both are expensive.

Maybe there are additional considerations/contraindications to using a borax/boric acid mix that I don't understand.