In my area (the Florida Keys) they significantly increase the heat of the home. A good alternative to pressure treated lumber is IPE. If one actually does a little digging they can find it from sellers close to the source and get it for pennies on the dollar. I did 2000 sq ft of wrap around decking for right at 10K. That was with me installing it, but pressure treated would have been 8K with me installing it.
Ipe is an amazing material. Found a lot of prefinished ipe flooring at a habitat for humanity store a few years back and did the top floor of the townhome I had at the time in it. Really beautiful and very resilient. It's become hard to find in tongue and groove flooring lately. Abundant for decking though.
