Bioclimatic (Passive Solar Heating)

Passive solar design represents one of the most important strategies for replacing conventional fossil fuels and reducing environmental pollution in the building sector. Depending on the local climate and the predominant need for heating or cooling, a wide range of passive techniques is now available to the building designer for new and retrofit building projects which, at little or no extra cost compared with conventional construction, can result in buildings which are both more energy-efficient and offer higher standards of visual and thermal comfort and health to the occupants.

Solar energy can make a major contribution to the heating requirements of a building. For most parts of Europe it is appropriate to use the following strategy:
  • Solar collection, where solar energy is collected and converted into heat.
  • Heat storage, where heat collected during the day is stored within the building for future use.
  • Heat distribution, where collected/stored heat is redirected to rooms or zones which require heat.
  • Heat conservation, where heat is retained in the building for as long as possible.
Direct Gain is the most common approach, with large, south-facing glazed apertures opening directly into habitable rooms in which are exposed appropriately-sized areas of heavy materials to provide thermal storage.

Indirect Gain systems include Mass, Trombe and water walls. Storage is in a south-facing wall, of considerable thermal mass, whose external surface is glazed to reduce heat losses. Movable insulation may be deployed at nighttime. The Trombe wall has vents at high and low levels to allow convective heat transfer to the occupied space, while the mass wall relies on conduction. Water replaces solid masonry in the third type. A development is the Barra Constantini system which uses lightweight glazed collectors mounted on, but insulated from south-facing walls. Heated air from the collectors circulates through ducts in the heavy ceilings, walls and floors warming these before returning to the bottom of the collector.

The sunspace or conservatory is a glazed enclosure attached to the south elevation, usually without auxiliary heating and with storage either in a heavy separating wall or elsewhere in the sunspace. It may be used to pre-heat ventilation air for the building. There has been a recent upsurge of architectural interest in glazed sunspaces and atria, especially in larger buildings.

In addition to special glazing materials (using special coatings or which operate electrochromically or photochromically), which can reject or help to retain heat, depending on the circumstances, entirely new construction materials are now being developed for the market which are often ideally suited to passive solar buildings.

Transparent or translucent insulation materials (TIM) are a new class of materials which combine the properties of good optical transmission and good thermal insulation.

0010One of the most obvious applications of TIM is on the sunny facades of buildings, replacing conventional opaque insulating materials. Well-designed TIM facades can reduce the annual energy requirements for space heating in new and retrofitted houses to one quarter that of comparable buildings with conventional wall insulation. Some transparent insulation materials are commercially available while others are still undergoing development. It is anticipated that large-scale production will significantly reduce their cost in the near future.
Passive solar heating strategy.

Passive solar heating configurations.
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