“At least two separate and independent factors cause discomfort in hot regions: the thermal sensation of excessive heat and the sensation of wet skin (sensible perspiration.) These two types of discomfort may occur either separately and independently or simultaneously.” 61

Discomfort occurs at 32-33C (90F) when sedentary, lower when active. 61

“The principle environmental conditions which determine the thermal sensation of heat are air and radiant temperatures, and air velocity over the body. Environmental temperature is a determinant of the effect of air velocity on the thermal sensation. At temperatures below approximately 33C (90F), heat sensation can be reduced by increasing air velocity. At an environmental temperature above 37C (98F), an increase in air velocity may increase despite a reduction in skin wetness.

“The feeling of skin moisture (sensible perspiration) created by the balance between sweat secretion and evaporation is the second factor determining the state of thermal comfort. The evaporative process is determined by ambient vapor pressure, air velocity over the body, and vapor permeability of clothing. In dry climates, sweat evaporates as it emerges from the pores of the skin surface without spreading over the skin, and thus the sensation of skin wetness is prevented.

“The thermal sensation of heat discomfort, without sensible perspiration, is characteristic of desert regions.” 61

“Usually, hot-dry regions experience local winds which are generally low in the mornings, increasing speed towards noon. By afternoon, the winds may reach maximum velocity and are frequently accompanied by sand and dry whirlwinds.” 61

“In the hot-dry climatic region, the integration of a courtyard into housing design is a common practice. The traditional design is a compact structure with an interior courtyard. Such a design minimizes the impact of solar radiation on the external surfaces.” 74

Iraqi courtyard example: there is a covered gallery surrounding the courtyard on two or three sides on the first floor; plants and water (fountain or small pools) add humidity 74

Givoni, B and Orlick, L, Planning for Comfort in Hot Dry Climatic Regions, in Desert Development : Man and Technology in Sparse-lands, Y. Gradus, ed., Boston: D. Reidel Publishing Company, 1985, 60-80.

Image: Bedouin Traditions Camp, Wadi Rum