When you're engineering your roof, you need to account for the potential snow loads. Brattleboro assumes a load of fifty pounds per square foot, but there are other towns in Vermont with higher numbers.
We're planning to use these joists for our roof because they allow us to do a clear span, and leave 24" of space for insulation as well as providing an easy opportunity to vent the roof--by installing a 3" EPS foam layer up against the top member, we leave a gap of about 1.5" above the foam, which serves as a vent.
Occupant behavior can make the difference between an efficient house and a wasteful one. Notorious energy hogs include plasma TVs, old refrigerators or freezers, ice-makers, and dehumidifiers. And don't overlook sneaky items like DVRs, always-on computer and entertainment equipment, etc.