Passive Solar design can be defined as setting out to use ambient or ‘free’ natural energy resources (in this case primarily the sun) to help produce a healthy, efficient, and enjoyable building, that has a decreased reliance on conventional fuels. The approach does this through an optimisation of the form, fabric and services of the building and through an integration of the building with its environment.
Passive solar homes range from those heated almost entirely by the sun to those with south facing windows that provide some fraction of the heating load. The difference between a passive solar home and a conventional one is design.
Elements of design include window location and glazing type, insulation, air sealing, thermal mass, shading and sometimes auxiliary heat.
There are three main design strategies all of which contain five common elements. Those described below are for the simplest design strategy, the direct gain system.
Aperture (collector): This is the large glass (window) area through which sunlight enters the building. Typically these should be facing as close to due south as possible, but within 30 degrees will still give significant gains. They should not be shaded by other buildings or trees.
Absorber: This is the hard, darkened surface of the storage element. This surface, which could be that of a masonry wall, floor or partition sits in the direct path of the sun and absorbs the heat.
Thermal mass: These are the materials that retain or store the heat produced by the sunlight. The difference between the absorber and thermal mass, although they often form the same wall of floor, is that the absorber is an exposed surface whereas thermal mass is the material below or behind that surface.
Distribution: The method by which the solar heat circulates from the collection and storage points to different areas of the house. A strictly passive design will use the three natural heat transfer modes i.e. conduction, convection and radiation. In many cases, however, fans, ducts and blowers may assist in the distribution of heat through the house (and cooling).
Control of heat is maintained through overhangs, which can be used to shade the aperture area during summer months. There are other elements that control under and/or overheating such as electronic sensing devises which include a differential thermostat that signals a fan to turn on, operable vents and dampers that allow or restrict heat flow, low-emissivity blinds and thermo-shutters.
For passive solar design to be effective it needs to be incorporated into a highly insulated structure. It has been determined that the best material to build houses is structurally insulated panels (SIPS). The main advantages of using these are:
The exceptionally high insulation value (i.e. low U-value) ensures a super insulated shell to the house
Minimal air leakage reduces energy losses considerably
The construction method used means the shell of the house can be erected in as little as two days.
The traditional roof truss is eliminated by using these panels which provides an extra living space in the roof.
More information on SIPS can be found by going to http://www.tekhaus.kingspan.com/uk/index.html
A video showing the construction of house using SIPS can be found at http://www.tekhaus.kingspan.com/uk/video/TEK_Haus_medium.mov