Thermal design of roof: A case study of PWD new quarters design, Malaysia / Nor Zaini Ikrom Zakaria

Nor Zaini Ikrom, Zakaria (2006) Thermal design of roof: A case study of PWD new quarters design, Malaysia / Nor Zaini Ikrom Zakaria. PhD thesis, University of Malaya.

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Abstract

The housing industry in Malaysia is faced with one of the challenges of sustainable development in the built environment; that is providing quality modern houses with respect to thermal and energy performances. This research was carried out to address this challenge and several related issues, which are energy efficiency documentation and guidelines for residential buildings in Malaysia, climatic design of modern houses to address the problem of thermal comfort and concerns on energy efficiency, and recommended climatic design features to be adopted. The aim of this research is to identify the thermal design of roof assemblage for optimum whole-building thermal and energy performances for low-rise detached residential buildings in Malaysia. The objectives are to quantify the optimum roof thermal parameters for best thermal performance, to apply the combined optimum roof thermal parameters and evaluate whole-building thermal and energy performances, and lastly to analyse the roof thermal design options pertaining to the thermal impact and cooling energy needs. The outcome is to contribute to recommendations for thermal design of the roofs for low-rise detached residential buildings in Malaysia. The investigations were performed via numerical simulation on computer using Tas as a thermal design tool. The Public Works Department New Quarters Design (PWD-NQD) double-storey bungalow was used as the building model. The performance evaluations were based on dynamic whole-building analyses for each roof model. The material and construction of the envelop were based on conventional practice. The roof thermal parameters are the external surface colour of roof covering, air space layer beneath roof covering, supplementary thermal insulation beneath conventional radiant barrier, ventilation or roof space, option for horizontal ceiling, and thermal insulation over horizontal ceiling. The respective computed optimum roof thermal parameters are light surface colour of roof covering, 50 mm of air space, 40 mm of supplementary thermal insulation, 10 air change per hour (ach) for roof space ventilation rate, and 20 mm of thermal insulation for horizontal ceiling. Selective combination of the optimum roof thermal parameters produced seven design options, each with models of four colours to consider the colour preference. The findings are compiled into charts for comparative performance evaluations of the roof thermal design options. All the design options reveal more significant thermal impact in the roof space than the selected occupied living spaces. The modest temperature modification found in the selected occupied living spaces results in a nominal thermal comfort improvement. The ultimate solution to augment the thermal comfort needs was provided by active cooling. While the thermal improvement is minimal, the impact on the energy for cooling needs indicated by the sensible cooling load is quite notable with a savings between 2.8 % to 12.6 %. This could be equivalent to an energy savings of up 2.1 % by the residential sector that translates to a national savings of 0.4 %. In conclusion, the findings of this study reveal some potential in climatically responsive roof design alternatives. Despite the nominal thermal modifications from the investigated roof thermal design options, the implication on energy for cooling needs is noteworthy in view of the emerging demands for active cooling to ameliorate the thermal comfort condition.

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