Natural ventilation and the effect on thermal comfort as sustainable strategies in dry hot arid climate: a Case study in Damascus. Kindah MOUSLI 1 ,Giovanni SEMPRINI 2 DIN University of Bologna, Via Risorgimento 2, Bologna 40136, Italy kindahmousli@gmail.com Keywords: Dry hot arid climates, natural ventilation, thermal comfort, traditional urban environment, Temperature. Abstract Dry-hot arid climate has specific characteristic especially in Mediterranean area, and traditional houses, which offer good examples for adaptive and sustainable respond. This paper aims to help promote energy efficient architectural design in dry-hot arid climate by reviving the use of natural ventilation process (cross ventilation, single side ventilation ‘stock ‘) and positive envelope properties of the traditional houses and urban traditional environment for courtyard housing clusters in a modern context. Such houses located in Damascus old city were traditionally renowned for their distinctive thermal comfort and adaptability. Four typical traditional houses are distributed inside and outside the ancient walls of old Damascus city (traditional urban environment, modern urban environment). Those houses are consist of two levels: the first represents the ground floor with heavy mass (stone), the second: with light mass (timber and dried mud structure). This house has different rooms size, windows distribution and different kinds of natural ventilation. Several monitoring data (air temperature, humidity and air velocity) were acquired during a hottest summer period, in parallel with occupancy survey, beside the studies of two houses, with the help of the dynamic computer simulations. The paper shows results of air temperature and other parameters related to different structure materials (intervention as concrete), natural ventilation, the opening windows (area and location), influence of urban environments. The comfort conditions were calculated according to adaptive model of ASHRAE and subjective survey are presented. Furthermore; simulation modelling was utilized to Verified results to contribute as strategies for sustainable design in this area. 1 Introduction Using natural phenomena to reach indoor comfort has been known since the early eras and the oldest architectures and engineering of the middle east region have responded with such phenomena as very good solution specially for dry-hot region (temperature and radiation height at the summer longest days light, big swing interval between day and night temperatures also between summer and winter). It realized the optimum comfortable temperature easily outside its urban environment and inside its houses throughout the most days of the yearlong. That was through equating with the volume adopting and the space taming with the different natural elements forces of the sun, atmosphere, biosphere and climate which are common in these days as passive design strategies and reducing energy consumption. As consequences for all these prefaces and looking at the native architecture engineering civilization view obviously that no separation between architecture, engineering, environment’s planning and the adopted human behaviour as they are in the old Damascus city . A real example, through absorb heating’s surplus throughout the creation of the integrated texture (thermal mass combine with the natural ventilation). If the old city Damascus were as detached in smaller masses as it is now, the outer surfaces were increased too much larger and exposed to the disturbances of cold-hot strikes waves and of heat either in winter or in summer. That means, each building needs an artificial ventilator. Therefore many researcher by worldwide specially at the Middle East and north Africa region have studied the passive control method of the traditional buildings which were comfort over years: [1] Ahmad E. (1985) monitored the traditional courtyard house within six centuries old indigenous urban cluster and compared it to a modern detached house within a new urban development under summer and winter climates of Ghadames, Libya. [2]Al-Hemiddi and Al-Saud (2001) studied experimentally the cooling in a building with an internal courtyard in a village house in Saudi Arabia. Changes in the courtyard ventilation were made by opening inner and/or outer windows in alternate ways