1) All sustainability is local. Just because a building is reported to work great in Austin or Chattanooga, don't think it will perform the same in the Northeast.

2) Use moderation in all things. Two people living a 12,000 square foot passive solar home is not an example of sustainability and is wasteful of the energy embodied in the materials.

Any basic home design can be a passive solar home if care is taken with:

3) Insulation - In New England, and at current and foreseeable energy prices, ceiling insulation should be a minimum of R-45, walls at R-20 or preferably above closer to R-30 and be sure to insulate the floors (heat can go down) to R-19.

4) Air Sealing - Too often this is an area that is skimped upon.  For best results use a full wall, 6 mil polyethylene vapor barrier and door and windows with good weatherstripping.  Building a vestibule or airlock entry also keeps the cold air leakage down. If you get below one air change per hour, consider an air to air heat exchanger for healthful levels.

5) Orientation - Ideally, the majority of the glazing should be within 20 degrees of true south. Trees grow and as they do so over a twenty year period and can destroy the value of a passive solar home's ability to function.  In addition, too often the basic home design is flawed by other portions of the home shading the south-facing windows

6) Fenestration - Placement of windows and doors should consider moderating non-south glazing with south glazing being 7% to 15% of the floor area .  Beyond 7% consider the need for additional thermal mass to prevent overheating. With unshaded west-facing glass having a low solar heat gain factor should be strongly considered. In addition, the U factor (inverse of R-value) ought to be the best that you can afford with at least ~.25 recommended for East, West and North windows and .33 for South-facing glass that will allow higher transmittance of useful light.

7) Be mindful of diminishing returns that usually kick in on some of these factors above. At some point, each additional inch of insulation, square foot of glass or inch thickness of thermal mass is less effective than the one that came before it.  A better rule is "some is good, more is better, enough is best". Learn to find the point of "enoughness".

                                                                                        (Con't.)