Direct Passive Solar Space Heating

The house is designed according to passive solar design principles in order to maximize the contribution of solar radiation in meeting the home's heating energy needs. Some of the main passive solar space heating design principles (for my property's specific site variables) are establishing an air-tight, high-insulation house envelope, incorporating adequate quantities of thermal mass, elongating the house on an east-west axis and facing the long south wall directly south and then incorporating adequate glass surface area in this wall, minimizing glass area on the remaining three walls, using appropriate colors schemes, and designing a small and open house.

The first, and most important, priority (and this applies to any house that requires significant heating and/or cooling at any time of the year) is to establish an air-tight, high insulation envelope to minimize losses of heating and cooling energy. It is pointless to attempt to heat a home that is not fairly air-tight as the home's hot air simply escapes through all the cracks and crevices in the home's envelope. And it is equally pointless to try to heat a home that has no insulation, as the hot air will simply transfer its heat to the uninsulated walls and those walls will immediately transfer that gain heat energy to the outside air. The more insulation, the better. The entire envelope needs to be well-insulated - walls, floors, ceinlings, doors, windows, utility entrances, etc. As I mentioned before, my house envelope is made completely of AAC, thereby establishing a relatively high insulation level throughout. The homogenous nature of the envelope construction helps eliminate thermal bridges where heat energy could 'leak'. The windows are double-paned low-e windows with good levels of insulation. The bedroom windows have built-in roll-down insulated exterior curtains that provide increased insulation when closed. The bathroom windows are kept extra small to reduce heat losses. I specially designed and built my own insulation curtains to cover the south wall windows at night and thereby markedly increase their insulation levels. The doors are also relatively high insulation. The doors and windows were joined to the walls by means of polyurethane foam in order to insure that the joints are air-tight, well-insulated and water-proof. Holes made to the envelope for wiring, plumbing and vents are also filled with expanding polyurethane foam. The floor of the house is further insulated by the relatively dead air spaces formed by the under-house crawl spaces. And the ceiling is further insulated by use of 'Arlita' for the roof incline formation. The sunroom that I will build to the south wall will further insulate the wall, windows and doors, as well as provide an air-lock for the entrances. And I plan to eventually apply a layer of thermal radiant insulation paint to all of the house envelope's interior surfaces, except for the tiled floors. This paint should significantly improve the envelopes insulation levels.

Practically the entire envelope and interior structure of the house is some form of masonry thermal mass. The AAC envelope provides moderate levels of heat absorption and release. The concrete slab-ceramic tile floors provide the greatest store of thermal mass. Also important are the interior brick partition walls. Most of the surfaces of the interior walls are either covered with a one centimeter layer of cement stucco or covered with ceramic or marble tiles. The masonry stove's soapstone themal mass is also very significant. Some other minor thermal mass components are the marble countertops of the bathrooms, the ceramic toilets and shower plate, the ceramic sinks in the bathrooms and kitchen and all of the kitchenware made of ceramics and glass. I plan to eventually substitute the fake marble countertops in my kitchen will real marble. And I am considering designing and building special sofa end tables made of wood or metal and glass filled with special PCM thermal mass.

The house is elongated from east to west with the south wall facing true solar south. This resulted in a long 17 by 7 meter rectangular house. The house was located in a spot within the property where the sun's winter sun would not be blocked from entering into the home's south, west and east windows by trees and bushes. The south wall incorporates most of the home's windows and allows for large (but not excessive, which could result in frequent overheating) amounts of solar radiation to enter the envelope. The east and west walls are limited to a single window; these windows are neither too small to be useless for solar radiation harnessing nor too large to threaten chronic summer overheating and unnecessary heat losses during cold winter nights. North wall windows are kept at a minimum - just enough to provide for adequate daylighting, ventilation and views.

Keeping the house small makes it easier to keep warm as there is less to heat. My interior open floor space is slightly more than 100m2; it is also important to attempt to keep the ceiling relatively low. My floor to ceiling height is 2.4 meters. More than this is unnecessary and wasteful of energy, less would be better. Of these 100m2, I try to keep the south half of the house, the master bedroom and bathroom, and the guest bathroom warm. I allow the master bedroom and bathroom temperatures to fluctuate more and be slightly lower than the south half of the house because this is a sleeping area that is basically only used at night when my wife and I are snuggly under a thick layer of blankets. The guest bedrooms only really need to be heated when they are in use, so they are often left somewhat colder than the rest of the house. An open floor plan also enables the heated air - heated by the sun, masonry stove, dump load, waste heat, etc. - to move freely to other colder areas; this way the solar heated air from the south half of the house can spread evenly throughout the south half open area and then flow into the bedrooms and bathrooms.

The future sunroom will provide an extra means of solar radiation harnessing, albeit an indirect passive solar means. The sunroom's large glass surfaces and relatively small enclosed volume will permit large quantities of solar radiation capture and relatively high air heating. This relatively hot air will flow into the house through the south wall's open doors and windows through their top half, causing a negative pressure in the sunroom that will result in colder floor-level house air to be sucked into the sunroom to replace the hot air that has moved to the house. The establishment of this thermosiphon cycle will make the sunroom a large solar thermal air heater that continuously heats the home's air throughout a cold but sunny winter day. I am also considering building special 'storm' doors that will go in front of the main entrance doors; these doors will be specially designed to meet several functions. The doors will be made of a wooden frame that permits two glass panels to be attached and detached from the door frame. When the door has the glass panels attached (in winter), the main doors can be left open to allow more sunlight straight into the home's interior to heat its thermal mass directly. At night, when the main doors are closed, the dead air spaces created by the 'storm' doors improve the insulation levels of the entrance doors. Furthermore, the main wooden frames of these storm doors will have special vent openings incorporated at their top and bottom edges to allow increased control of the air flows created by the sunroom's thermosiphon effect. Lastly, in summer the glass panels will be replaced by mosquito net panels that allow the main entrance doors to remain open during the night to allow increased night flushing of the thermal masses' accumulated daily solar heat energy and to allow the doors to remain open to better channel cooling air breezes in the evenings.