In order to construct buildings that naturally preserve the comfort of occupants with minimal use of imported energy resources, the following basic design issues must be considered:

The building envelope, which consists mainly of its roof, floor and exterior walls, must perform two critical energy-preserving functions. Surfaces exposed to the outer environment should be well-insulated to minimize unregulated heat gain or loss. In addition, these building elements should be built from massive materials with a high thermal capacity, enabling them to selectively store and release excess heat during different parts of the day. A proper combination of interiorthermal mass and external thermal insulation can be used to maintain a stable temperature in the building, despite the widely fluctuating conditions outside and the human activities taking place within.

  • Window openings should be strategically oriented and treated to admitsolar radiation in winter, when it can be taken up by the building's thermal mass and used for passive heating, and screen it out in the summer to avoid overheating. This selective solar control can be achieved by maximizing the glazed areas facing south (which are exposed to low-angle winter sun) and minimizing those facing the east or west (which are struck by intense morning and afternoon sun in the summer). Exterior shutters can be selectively operated to shade windows from direct and indirect radiation on summer days, and to insulate them against excessive heat loss on winter nights.
  • Passive climatization of a desert building can be achieved by capitalizing on natural energy flows, in particular, the use of night ventilation for cooling. When window openings are appropriately placed with respect to prevailing winds, the building's internal mass can be flushed with cool air at night. This reduction in temperature allows the entire structure to passively absorb excess heat from the interior space during the hottest hours on the following day.

 

Animation of paths taken by the sun in winter and summer.

Note that the winter sun moves from east (E) to west (W) when tilted to the south (S), a situation known as low-angle sun. In summer the sun travels much higher in the sky. Due to low-angle radiation, the daily "insolation" (INcoming SOLar radiaTION) falling on a given area in winter is lower than in summer. The scale at the bottom gives the color coding of insolation levels reaching the earth.


 

Animation of bioclimatic building design for winter comfort.


In winter, sunlight is allowed to pass through southern windows during the day (6 a.m. to 6 p.m.), thereby heating the building's thermal mass. At night (6 p.m. to 6 a.m.), the window is insulated to prevent excessive loss of heat to the cold outside environment. Note from the temperature graph below that, while the outside average winter temperature increases from 5oC at 6 a.m. to about 19oC at 3:30 p.m., the inside temperature ranges from a 18oC at 6 a.m. to about 24oC at noon, providing comfortable living conditions without external heating.

 

Animation of bioclimatic building design for summer comfort.


Observe how shading closed windows with shutters during the daylight hours (6 a.m. to 6 p.m.) and opening the windows at night (6 p.m. to 6 a.m.) to allow cool air to enter a well-insulated structure provides a fairly comfortable environment throughout the day. The temperature graph below indicates that although the outside temperature ranges from a low of about 16oC at 6 a.m. to a maximum of 34oC at about 3:30 p.m., the inside temperature remains at a nearly constant 25oC throughout the day.

 

BIDR researchers have adapted these principles of bioclimatic design to the particular conditions of the Negev, and shown that their implementation in residential buildings can eliminate most of the need for heating in winter and all of the need for summer cooling. In a comparative study of lightweight and heavy structures built for immigrant housing, architects David Pearlmutter and Isaac A. Meir (1995) found that the financial costs of disregarding these basic climatic design principles is much more severe for buildings constructed in the harsh conditions of the desert than for those in the climatically moderate population centers of Israel's coastal plain.

In addition to its fundamental application in building design, each of these issues - the building envelope, window openings, and passive climatization - has been the subject of further development and innovation by the BIDR's desert architecture researchers.​