Here: https://bitcointalk.org/index.php?topic=3707.msg53879#msg538...

"The best thing about my water cooling and floor heating is that my wife keeps nagging me to buy a second 5970 to make the floor warmer. Beat this with a air cooled system."

That has been done already http://bitfury.org/bitfury110.html

    using mining equipment to produce hot water and house heating

Those who bought old one, now f$%&^d up. New line of mining HW is order of magnitude cheaper.

Hot water preheat wouldn't be too hard to do, and would save serious money in colder climates. Maybe someone could work a deal with an apartment complex? (Hot water preheat for rent?)