Some Ask Umbras past come a-haunting this week, as our tireless research slavette returns to the questions of home heating, water heating, and -- just to mess up our "heat" theme -- battery recycling. As always, the incomparable Umbra punctures myths with rapier wit. It turns out wood stoves aren't necessarily as eco-bad as you thought, and tankless water heaters aren't as eco-good. Find out more about these matters, and Umbra's new slogan, in Ask Umbra -- only on the Grist Magazine website.