This post is not so much about Amador County Real Estate as it is about green building and general knowledge.

Lots of people toss around “green” statements, one of the most common, often misused term in listings is “PASSIVE SOLAR DESIGN”. Now its not that these people are being dishonest or even trying to fool you. Its just that the term is not officially defined, so it is very unclear. I want to help clear it up for you. That way when you look at a house that someone has claimed to be “passive solar” you will have some background to decide for yourself if the claim is warranted.

The U.S. Dept. of Energy explains that a building needs five elements to constitute a “complete passive solar home design”.

Starting from the Sun,

The Control:

Site planning is a big part of passive solar design. Depending on your climate, things like building toward the bottom of a valley where cool air will stay longest in the morning, the top of a hill where cooling breezes will be common, or part way up the north slope of a valley where you are less likely to have shade from the other hills but still below the wind, all play parts in site choice. Most people just call any house with the majority of windows facing South “Solar”, and in most of the U.S. building with the long axes in the East-West direction and the windows facing within 30 degrees of “True South” is part of solar design.

Intensionally placed trees and properly designed roof overhangs are a big part of passive solar design.
Choosing and planting trees with passive solar control as a consideration can net huge savings year round. Think about the size the tree will be, whether it will lose its leaves in the fall, and think about the shade it will through throughout the year. Most designs will want to shade the house, especially the windows in the summer, but let as much light (and heat) as possible come in during the winter.
Roof overhangs can also be designed to maximize this consideration. Things as minor as low-emissivity blinds; and awnings can make impressive savings in cooling during the hot summer months.

The next thing in order from the sun are the apertures or collectors.

Those are fancy technical names for windows. Typically, as mentioned above, the majority of the glass should face South or at least within 30 degrees of South. Here in the Northern hemisphere the sun traverses the sky from someplace South of due East to someplace South of due West, the whole day, always South of a straight line curving overhead from due East to due West, so to let the most light in, focus window (aperture) placement on the South side of the house. Try to plan your site so that the windows are not shaded from 9:00 a.m. to 3:00 p.m. during the heating season.

Next is the Absorber.

Usually but not always this is the facing surface of the thermal mass or heat sink. For now let’s talk about the surface. It should be dark, The reason that it looks dark is that it absorbs light. It seams obvious when you think about it as a function of color theory. Things that reflect light look light. Things that absorb light look dark. In this case you want a dark surface to absorb that light and heat. Masonry wall, dark flooring, even water can work well.

After the absorber is the Thermal Mass.

Often the thermal mass is just the inside of the absorber. If you pore a monolithic slab floor and do a dark stain or set dark stone directly to the slab the hard dark surface is the absorber and the heavy slab is the Thermal Mass. This is what stores the heat. To spread it out over time.

Last is Distribution.

Distribution is the method by which the solar heat held in the Thermal mass circulates to different areas of the house. A strictly passive design will use one or more of the three natural heat transfer modes—conduction, convection, and radiation—exclusively. But in many applications, however, fans, ducts, and blowers may help with the distribution of heat through the house.

So look for these five features on houses you visit, and before you know it you will get a feel for what houses are and are not up to the claim of “Complete Passive Solar Design”. As always feel free to give ma a call or zap me an email, or click by