ABSTRACT
Thermal comfort is recognized as a key parameter for healthy and productive large workspaces found in office buildings. Achieving occupants comfort is a priority that has a great effect on energy demand in buildings, particularly in hot climate zones. The study aims at investigating a suitable aspect ratio of building form that will reduce the costly effects of providing thermal comfort to occupants in buildings in a hot-dry climate of Nigeria. A case study approach was adopted to study the geometric properties of existing similar office buildings which were chosen purposively and a quantitative research method was used for the collection of data through computer simulation. Firstly, the study examined the thermal performance of different building forms with the same floor area against their volume to surface ratio (V/S). Forms with good thermal performance were optimized with different aspect ratios elongated along east-west orientation. ECOTECT program was used to study the energy performance of the forms on exposed surfaces. From the deduction of the study, the west and south surfaces are the most exposed (in terms of heat gain and incident light), both the cube and cylinder forms were optimized with various aspect ratios and simulations were conducted to observe the extent to which solar radiation could be reduced on exposed west surfaces during hot periods and maximized on south surfaces during cold periods. The study showed that a slight change in the volume to surface ratio could have a significant impact in a building's energy performance, and also significant thermal environment can be attained during both hot and cold periods when optimized with an optimum aspect ratio of (1:1.7) as compared to aspect ratio (1:1). 33% and 28% energy are further saved on south and west surfaces respectively when aspect ratio "1:1.7" (ideal ratio) is compared with aspect ratio "1:1". Also, it was noted that the incident solar radiation decreases from aspect ratio 1:1.7 indicating 71% exposure, 1:1 and 1:2 indicating 72% exposure, 1:2.5 indicating 73% exposure, 1: 4 indicating 77% exposure and 1:3 indicating 78% exposure. Therefore, it could be said that an ideal aspect ratio of 1:1.7 existed for the wide range of ratios from 1:1-1:4. In conclusion, the thermal comfort of the proposed building could be optimized by applying the aspect ratio "1:1.17" of cylindrical/cuboidal form to reduce the effect of west and south solar radiation. It is recommended that prospective designers should go beyond only orienting buildings on east-west axis, rather, effort to experimentally explore different aspect ratios should be considered for befitting alternative.