Keeping cool in Cairo : thermal simulation of passive cooling in dwellings

• Main Author: Sheta, Wael A. M.
• Published: University of Sheffield 2012
• Subjects: 693.8
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.578035

Cairo is one of the World's mega cities, with associated problems of overcrowding and suffering from problems such as pollution, traffic congestion and a shortage of dwellings and services. The new suburbs and communities around Cairo playa vital role in decreasing these environmental, social and economic pressures upon the city. According to the national planning scheme, the main aim of these communities was to address problems associated with air pollution, traffic and a shortage of housing. In addition, these developments were planned to deliver sustainable communities and lifestyles for future generations. This research studies El-Tagammu' El-Khames, one of the new urban settlements developed around Cairo. It is considered to be the new premium residential district of Greater Cairo. Unfortunately, most of the properties in this development are poorly adapted to the prevailing climate and an understanding of what constitutes a sustainable community is still one of the missing links in the Egyptian planning process. This thesis describes a field study and a thermal simulation analysis carried out for a typical dwelling in El-Tagammu' El-Khames. Internal and external temperatures were recorded for two periods in summer and autumn. The recorded external temperatures were used to validate the weather file proposed to be used in simulation. The recorded internal temperatures were used to validate the internal temperatures predicted using the simulation tool. Thermal simulation (Design-Builder) was then used to simulate the effect of a number of passive cooling strategies on the thermal performance of the house during peak summer. These strategies included a range of orientations, thermal conductivity (U-value), thermal mass, night ventilation and shading devices, and these were investigated as they are simple steps that could be applied to new and existing dwellings. An incremental approach was adopted, starting from a basic house model, investigating variations of a particular parameter, and progressing the optimum for that parameter as the basis for the next set of analyses. It was found that three modifications would improve thermal comfort in the dwelling studied such that air conditioning should not be necessary. These were to extend the time at which night ventilation ended (i.e. windows were closed) from 5:00 am to 10:00 am; to insulate the external wall; and to provide solar shading. This impact of these proposals was validated by confirmation of the effect of surrounding buildings, by repeating the analysis for other periods of the year (i.e. winter season), Technical recommendations drawn by comparing the real case with proposed model through different periods of the year, enable appropriate solutions for architects, designers and engineers to be chosen at the early stages of a design for new dwellings and well as existing developments to achieve low energy thermal comfort and keeping buildings cool in Cairo.