Elements of passive solar design

E very passive solar building includes five distinct design elements:

1. An aperture or collector — the large glass area through which sunlight enters the building.

2. An absorber — the dark surface of the storage element that absorbs the solar heat.

3. A

   Elements of passive solar design, shown in a direct gain application.

   thermal mass — the material that stores the absorbed heat. This can be masonry materials such as concrete, stone, and brick; or a water tank.

4. A distribution method — the natural tendency of heat to move from warmer materials to cooler ones (through conduction, convection, and radiation) until there is no longer a temperature difference between the two.

5. A control mechanism — to regulate the amount of sunlight entering the aperture. This can be as simple as roof overhang designed to allow more sunlight to enter in the winter, less in the summer.

Main features of passive houses design

• the air is fresh and very clean but dry (especially during winter).

• Due to the high resistance to heat flow (high R-value insulation), there are no "outside walls" which are colder than other walls.

• as there are no radiators, there is more space on the rooms' walls.

• inside temperature is homogeneous; it is impossible to have single rooms (e.g. the sleeping rooms) at a different temperature from the rest of the house.

• the temperature changes only very slowly - with ventilation and heating systems switched off, a passive house typically loses less than 0.5 °C per day (in winter), stabilizing at around 15 °C in the central European climate.

• opening windows for a short time only has a very limited effect - after the windows are closed, the air very quickly returns to the "normal" temperature.

Peculiarities of passive solar construction

1. Space heating

Passive house buildings make extensive use of their intrinsic heat from internal sources – such as waste heat from lighting, white goods (major appliances) and other electrical devices (but not dedicated heaters) – as well as body heat from the people and animals inside the building. Together with the comprehensive energy conservation measures taken, this means that a conventional central heating system is not necessary, although they are sometimes installed due to client skepticism.

2. Superinsulation

Passive house buildings employ super insulation to significantly reduce the heat transfer through the walls, roof and floor compared to conventional buildings.

3. Air tightness

Building envelopes under the passive house standard are required to be extremely airtight compared to conventional construction. Air tightness minimizes the amount of warm (or cool) air that can pass through the structure.

4. Ventilation

Mechanical heat recovery ventilation systems are employed to maintain air quality, and to recover sufficient heat to dispense with a conventional central heating system All ventilation ducts are insulated and sealed against leakage.

5. Typical passive house windows

Windows normally combine triple-pane insulated glazing with air-seals and specially developed thermally-broken window frames.