AIR SHAFTS AND THERMAL PERFORMANCE IN RESIDENTIAL BUILDINGS UNDER HOT-ARID CLIMATE ZONE IN SAUDI ARABI

Abstract

The significant rise of housing projects in Saudi Arabia, particularly apartment buildings, leads to energy consumption. Residential buildings consume 51% of the electricity in the building sector, and air conditioning represents 70% of the total national electrical demand. Alternatively, using natural ventilation in buildings improves thermal performance and reduces energy consumption. One of the effective strategies to increase natural ventilation in buildings is the use of air shafts. The function of the air shaft is to provide daylight and fresh air into the buildings; however, recently, it has been used to install outdoor air conditioning units and plumbing pipes. As a result, the air shafts became a source of heat in the middle of the building, causing increased air temperatures in the rooms adjacent to it. This also leads to the poor thermal performance of the building and results in higher energy consumption for cooling. This research investigates the possibility of improving thermal performance in apartment buildings by optimizing the air shaft design in a hot-dry climate. Field measurements were carried out by using data loggers on an existing low-rise (threestories) apartment building for one year to assess the current thermal performance of the apartment building with an air shaft. The measurements included the external and internal environments by measuring the air temperature and relative humidity of the three levels of the air shaft and the connected rooms. The field measurements showed a significant difference in air temperatures between the outdoor and air shaft. The maximum, minimum, and average air temperatures for the hot, cold, and normal months were higher than the average outdoor air temperatures. The difference in air temperature was not constant for the connected rooms, but it was generally higher in the third level than in the first and second levels. The field measurements proved a need to improve the thermal performance of the air shaft and connected rooms. The collected data from the field measurements were used as reference points to build the base model. The validation of the base model and different proposed models have been done using the building performance simulation tool, which is DesignBuilder. Systematic methods were employed to develop air shaft design models based on the most effective air shaft design parameters based on air shaft envelope and configuration. The design parameters included the following factors: window glazing type, window-to-wall ratio (WWR), thermal insulation thickness in the wall, air shaft length and width, and air shaft floor design. The optimum air shaft model is 9m high, 2m in length, and 2m wide, with six windows with WWR of 30%, double glazing type with solar heat gain coefficient (SHGC) value of 0.568, and a U-value of 1.761, thermal insulation thickness in the wall is 10 cm. The optimum model reduced the total cooling loads yearly by 16.94% compared to the base model. In conclusion, the research findings found that the proposed optimum design model of the air shaft could enhance thermal performance and reduce energy consumption in buildings in a hotdry climate in Makkah, Saudi Arabia.