AUGUST JLC 1998 Straightening Out Those Plastics To the Editor: Thanks for a generally great article on alternative decking materials. Unfortunately, the author uses the term "vinyl" to describe any plastic product, which is incorrect. Vinyl is a common term for PVC, or polyvinyl chloride. Most of the recycled plastic decking materials mentioned in the article are not vinyl at all. They are primarily high-density polyethylene (HDPE) from milk jugs, detergent bottles, and the like. Most of the actual vinyl (PVC) products mentioned contain little or no recycled content. From an environmental perspective, there is a huge difference between recycled polyethylene and virgin PVC. Nadav Malin Environmental Building News Brattleboro, Vt. Foam Sheathing Too Weak To the Editor: In the article "Two-By Debate Continues" (Notebook, 6/98),