Experimental evaluation of summer thermal comfort in various types of Sardab (Cellar): underground space in Iran vernacular houses

This article aims to evaluate the effect of three types of Sardab (Cellars) on thermal comfort conditions. Two vernacular buildings in Yazd have been selected as case studies. In the Rasoulian house, a sardab with a water pond has been defined as case A and a Sardab without pond has been chosen as case B. Case C is a Sardab without pond in Mortaz house. Using experimental data, environmental parameters were analyzed for a month in two consecutive years. Using measured data, the values for Predicted Mean Vote (PMV) and Predicted Percentage Dissatisfied (PPD) have been calculated. The results show a considerable reduction in the air temperature (up to 20 oC) and an increase in the relative humidity of the air (up to 50%) in case A (the Sardab with pond). The sardabs without pond (Case B and C) presented lower efficiencies. Variations in daily temperatures have been presented in three cases with ceilings elevated at different heights. While the sardab that is placed completely underground presented the lowest temperature, in two other sardabs, the average air temperature was 2-3 degrees higher. According to the results, in a hot and dry climate, application of all sardab types, either with or without a pond, elevated or underground, would improve the thermal comfort condition and the energy efficiency of buildings.