“Solar Energy” discussions of the two distinct types are frequently muddled: Passive Solar & Active Solar. Ironically the “Active” version, with the symbolic PV (Photo-Voltaic) roof panels generating electricity is usually the first visual image when hearing “Solar Energy”. We’ll discuss Active later and the significance of both working in tandem.
Passive Solar essential focus is the design and construction of a home in relation to the Sun’s natural path. The home’s designer should utilize as many of the following elements:
· South facing location for home (major wall)
· Rectangular shape along East-West axis
· Majority of windows along the long South wall
· Minimal windows on North & West sides, very few on East side
· South roof overhangs lengths set by latitude ratio over medium, not tall windows (less than 60”)
· Significant “Thermal Mass” on South side of home near large South windows
A brief technical brief expansion on each of these elements may assist the curious.
First, the South-Facing orientation is by far the most significant. Even one reasonable portion of the house facing South can help if a site minimizes the ideal. Using the preferred rectangular structure’s long side facing South, the potential Sun energy gain is maximized. The designer clusters key rooms like the Great Room, Master and Guest Bedrooms, and maybe even the Dining room along this longer South wall. (And possibly the “View” side also for our beautiful North Georgia Lake and Mountain settings!). The secondary rooms, like bathrooms, closets, etc. then fit on the North side of the home. If the lot is sloped southward also, the potential daylight basement space also benefits.
Now with our “Passive” Solar house bringing in this energy, we need to properly regulate those South windows when we want it (winter) and keep it out when our Georgia summer is peaking. The Sun’s path is at a maximum angle at 79 degree noon angle on June 21 while the low angle of 31 degrees is on December 21. For North Georgia, a South roof overhang of about 20” long, with 54” high windows, is a good design starting point. Simply summarized, this overhang will shade the South Windows in the warmer months and lets most of the sun enter the house in the colder months. (both Light & warmth in winter!) Note that this shading concept only works effectively on the South side, thus minimizing windows on the other sides is important also.
This “free” energy boost must be tempered by thermal mass to store the energy and modulate it over time.
Good thermal mass examples are fireplace stone or brick, some internal brick or stone walls, and ideally, a concrete floor with chosen finished pavers. . A moderate sized (1500 s.f.) “Green Certified” style house like LEED or EnergyStar rated can easily pick up ½ to ¾ ton of Passive Solar heating. Thus…. we may only need a 1-1/2 to 2 ton size heat pump for this home!
With these few Passive Solar concepts at work, our home is more comfortable, and is saving energy costs. Now….our home is better prepared to add the “Active Solar” system later!
For more information you can contact Art directly at This email address is being protected from spambots. You need JavaScript enabled to view it. or visit his website .
