Safely maintaining building comfort uses quite a bit of energy. Much less so in efficient buildings.

There are several standards, web sites, and ratings systems for energy efficient buildings (readers, pleas add your favorites and not-to-favorites ;).

Some basic web sites:

• http://buildingscience.com
• http://greenbuildingadvisor.com

Basics

• The Perfect HVAC System (BS) really made Soren's day when he found it
• The Perfect Wall (BS) 

Insulation

•  Dense Pack Cellulose (great for retrofitting walls, not so much near roofs)

Roof-related

•  Understanding Attic Ventilation