Weather
Temperatures in these zones range from 10 degrees to 120 degrees F. Sunshine is predominant, with over 85% of available hours bathed in clear skies and sunlight. The highest wind velocities are most often in afternoons during spring and fall. Winds over 20mph may be dust-laden. Night winds are often cooler, coming down from the mountains as the cool air is heavier and prone to behaving like water, flowing downhill. This can be used to advantage for nighttime cooling of structures if the buildings are at the base of mountains or within valleys. These areas are prone to afternoon precipitation in summer “monsoon” season of June through August, if at all. Average yearly rainfall is usually under 20 inches, except in mountains, where snow is likely in winter. Water conservation, greywater use, and rainwater collection are vital. Low humidity allows for unique solutions in evaporative cooling.
Massing (For farming compounds and towns)
The best means of building multiple buildings in this case uses courtyards, patios, and stacked mass construction of adobe or similar materials, similar to the style of the pueblos of the American southwest, known as “shaded dense” planning.
Site / Landscape
High altitude locations are excellent. Sites at low level but above valley floors can benefit from cool air flow. Site near water bodies and waterways are ideal locations for desirable effects of microclimate. Outdoor living areas are very useful here, especially when enclosed in a courtyard or garden with high mass walls, trees and vegetation, a fountain or pool in the center, east or north side, and trellises or other shade devices over the main part of the living area. Raised roof structures that provide a “clerestory” over these areas are also well-suited. Patios and portals are ideal on the south and east sides of the structure. Low plants and grasses to provide for radiation deflection are very desirable.
Sloped sites are ideally located with south and southeast slope exposures. East and west walls should be shaded with trees and gardens if possible.
Building Form
With dry heat comes a need for compact homes that are built of high mass materials like adobe. Building them ever closer together, either directly adjacent or stacked, creates a volume effect of temperature lowering. Subterannean spaces are lovely in this climate zone, as earth temperatures tend to stay around 50 degrees. Framed construction is least desirable. High ceilings are not necessary. Covered walkways around the interior courtyards provide for smaller cooler living spaces with access to cooler air in shaded courtyards. Non-inhabited spaces (garages, workshops, etc) should be placed in the west to minimize heat impact. Ideal building dimensions are 1:1.3 oriented East-West at from due south to 35 degrees east of south. 25 degrees east of south is most ideal. Low pitch, flat, and domed roof structures minimize solar heat gain and provide the most wind resistance. Shaded roofs are even better. Hard edges disappear in the desert, so fluid organic forms can be used to create delight in the building’s form and will also help direct wind flow. Wind chimneys as found in the Middle East are viable. Shading devices are absolutely necessary on the south and west sides of the building, preferably zero-gain type such as roofs and portals. Smaller window sizes minimize solar gain. Windows should be set high to minimize ground reflected radiation. External shading is ideal. Opening facing south, north, and sometimes east are ideal. Walls of living areas are best suited to heat-storing materials like stone or mass adobe or insulated concrete. Walls in bedrooms are acceptable to be lightweight, even framed, and with open or nearly open roofs in outdoors living areas. Exterior colors should be light on outwards facing walls, bright colors are appropriate. Dark and medium colors can be used on downwards facing surfaces like the undersides of eaves and porches to minimize secondary reflection. Solar power is entirely feasible in these locations, as is often wind.
