Is polypropylene (PP) siding a greener substitute for PVC siding?
CertainTeed offers shake-style siding made of polypropylene (PP). I read other questions on this site asking for greener substitutes to PVC and have seen fiber cement board given as an answer. Fiber board needs maintenance. I haven't found anything on this site about polypropylene (PP) shake style siding, and it sounds like a great substitute for PVC, since PVC will emit harmful chemicals throughout its lifecycle and if burned. I am hoping to hear that PP is greener substitute. Also, we live in NJ and currently have cedar wood shakes. Should the plastic siding go up over the shakes? A contractor said he would remove the rotting/bad shakes, replace them with plywood and put 1/2" Dow foam insulation over the good shakes and plywood and then put on the siding. He said this will add to the insulation and soundproofing. Is it okay to put the siding up over the wood shakes? How can you be sure there won't be rotting/mold or bugs still there?
PP siding is greener than PVC siding. It is also easily recycled.
However, I would recommend fiber cement over either PP or PVC. I also live in NJ and have designed a LEED Silver certified, net-zero-energy home that was built two years ago with the fiber-cement, cedar-shake-pattern siding. If you select one of the standard colors available, fiber cement comes prefinished with a 50-year warranty on the finish, and is therefore very maintenance-free.
CertainTeed makes this product, as well as Johns Manville, but CertainTeed's version is made in the U.S. and does not use tropical woods in its mix.
I would not recommend putting up new siding over the shake. Frankly, if the cedar shake is not in seriously bad condition, refurbish and keep it.
For more information:
Read "What's the best affordable sustainable siding option? Any thoughts on roofing materials and gutters?" a Q&A answered by Carl Seville.