Thermal Efficiency of Courtyards for Residential Buildings in Iraq

Abstract

This thesis investigates adopting the courtyard pattern in Iraq to provide a thermally efficient architectural solution that contributes towards solving the housing challenges in the country. As a result of more than three decades of wars and instability, the country suffers from having a large housing shortage and a major production shortfall. This shortage is estimated at around 1.0 million housing units, which is equivalent to one-quarter of the total housing stock in the country. The current housing production is around 30000 housing units per annum only, which, therefore, does not alleviate the housing needs in the country. The country has developed a new national housing policy and adopted the mass construction of multi-family buildings as an architectural solution towards solving the large quantitative problems. This research aimed to investigate the potential thermal efficiency of courtyards with considering this housing context. To achieve this aim, this research started by investigating the housing context in Iraq. It, then, focussed on the use of courtyards in modern multi-family residential buildings in Iraq, and explored the level of thermal comfort that courtyards can offer to Iraqi residents. The study developed a novel Courtyard Thermal Usability Index (CTUI) to quantify the ability of courtyards to offer a thermally comfortable environment to occupants. CTUI is the fraction of thermally comfortable hours in a courtyard to the total occupation hours during a specific period. To underpin the quantification, the research conducted a thermal comfort survey in Iraq and carried out a series of simulation experiments. The aim of the survey was to determine the thermal comfort limits of Iraqis to be used in judging the thermal efficiency of courtyards. The aim of the simulation was to explore the thermal conditions of courtyards in Iraq. Two simulation tools, Envi-met and IES-VE, were used to determine the thermal conditions across a search space of 360 different courtyard variants. The simulation experiments were conducted for Baghdad and six other Iraqi cities of different climatic conditions. The tested courtyards represent a wide range of possible courtyard geometric configurations, which enabled the research to provide a good overview of possible thermal conditions of courtyards in Iraq. The survey results indicate that the minimum and maximum thermally comfortable globe temperatures for Iraqis in winter and summer are, respectively 14 °C and 35 °C. Within this comfort range and during the daily occupation hours, which are from 8:00 to 22:00, the annual CTUI of courtyards, in Baghdad, ranges between 0.16 and 0.38. Expressed in a different way, courtyards can offer 875 - 2078 comfortable hours out of 5470 occupation hours per annum. The rest are not comfortable hours, mostly due to overheating. In comparison to current typical urban settings, courtyards offer higher levels of thermal comfort. The most effective geometric property on courtyards’ thermal conditions and the level of thermal comfort in courtyards is the width/height ratio. This ratio has a significant impact on the insolation level and Mean Radiant Temperature, which highly affect the thermal sensation of occupants. In conclusion, this research suggests that the courtyard can help to provide thermally comfortable environments for occupants in Iraq. However, other passive and active strategies need to be considered as courtyards are not comfortable for around two-thirds of the occupation hours around the year. This research advances the knowledge on the acceptable thermal comfort conditions in residential buildings in Iraq through presenting the first complete thermal comfort survey in residential buildings in the country. This research presents the first attempt towards a holistic and comprehensive assessment of thermal comfort in courtyards.