|Siti Halipah Ibrahim||Department of Civil Engineering, Faculty of Engineering, Universiti Malaysia Sarawak, Kota Samarahan 94300, Sarawak, Malaysia|
|Qairuniza Roslan||Department of Civil Engineering, Faculty of Engineering, Universiti Malaysia Sarawak, Kota Samarahan 94300, Sarawak, Malaysia|
|Rohaida Affandi||Department of Civil Engineering, Faculty of Engineering, Universiti Malaysia Sarawak, Kota Samarahan 94300, Sarawak, Malaysia|
|Abdul Wafi Razali|
|Yon Syafni Samat|
|Mohd Nasrun Mohd Nawi||School of Technology Management and Logistic, Universiti Utara Malaysia, Sintok, 06010, Kedah, 06010, Malaysia|
One of the major problems in modern housing design is overheating. Occupants suffer higher indoor temperatures due to a lack of natural ventilation. This issue arises because of poor passive design. A good passive design promotes natural ventilation and provides better indoor air temperatures without reliance on mechanical cooling systems. The roofing system plays an important role in a house’s design. Since the roof contributes to 70% of the total heat gain, it is important to investigate its design to reduce the impact of overheating. It has been found that many roofs lack a ventilation system in the top part of the house. These openings in the roof provide areas for trapped hot air to exit into the environment. The openings also enhance natural ventilation and allow for effective air circulation inside the house. The optimum roof is designed to tackle this matter by reducing the overheating inside the house, especially during the hottest hours of the day. The hot air exits based on the differences in air density and due to prevailing wind. In this study, the optimum roof was tested on a small-scale model and verified by simulation using computational fluid dynamic (CFD) software, namely ANSYS 18.0. From the data obtained, it was proven that the opening in the roof reduced the indoor temperature. In conclusion, the optimum roof could improve the passive design and help to reduce overheating inside a house.
Computational fluid dynamic simulation; Heat transfer; Optimum roof; Ventilated roof
Malaysia is located in the equatorial region and experiences high temperatures with high relative humidity throughout the year. The average solar radiation in this hot, humid climate is between 4.21 kWh/m2 and 5.56 kWh/m2, annually (Azhari et al., 2008). Malaysia receives 8.7 hours of sunlight per day (Malaysia Meteorological Department, 2014). The recommended thermal comfort level ranges from 25 to 28°C (Ibrahim, 2004). Based on a previous study on concrete terrace houses in Malaysia, indoor temperatures are only comfortable to the occupants for a few hours every day (Ibrahim et al., 2014a). The same study also discovered that the indoor temperature could reach more than 30°C during the daytime. Increased indoor temperatures in a building are due to poor passive design. Designers should adapt more natural ventilation as part of the passive design, especially at the top part of the house. The reason for focusing on the top part of the house is because hot air rises from the bottom part of the house to the upper part due to density differences. The differences between the outdoor air pressure and the indoor environment creates suction. Hence, the hot air naturally passes from inside the house to outside without depending on a mechanical ventilation system.
Poor passive design could lead to overheating. In addition, the occupants in modern low-cost housing suffer overheating due to poor ventilation and roof design problems (Ibrahim, 2004). One research study found that the recorded indoor temperature of a modern low-cost house was higher than recommended for the occupants’ level of comfort (Tinker et al., 2004). Due to this, occupants rely on mechanical means to cool their houses, which incur energy consumption costs to power the electrical components. A previous study concluded that openings in the roof’s surface could help to reduce the indoor air temperature (Ibrahim et al., 2014a). This study focuses on roofing because it plays an important role in controlling the amount of heat transmitted from the roof surface into the internal area.
This study concluded that the openings on the roof surface provided additional ventilation for the house. The optimum roof works best when the condition of the house is fully closed and fully opened condition. The optimum roof showed its significant reduction of indoor temperature under fully closed condition. This concluded that the openings on the roof surface played an important role in reducing the temperature inside the house. The optimum roof helped to reduce the indoor air temperature by up to 10°C compared to the normal roof.
The authors would like expressed appreciation to Universiti Malaysia Sarawak (UNIMAS) for providing staff, a laboratory, and other facilities to assist with this research.
Abdul Rahman, M.A., Abdul Samad, M.H., Bahauddin, A., Ismail., M.R., 2009. Towards a Low-energy Building Design for Tropical Malaysia. Universiti Sains Malaysia, Penang, Malaysia
Ali, B.H., Gilani, S.I., Al-Kayiem, H.H., 2014. A Three-dimensional Performance Analysis of a Developed Evacuated Tube Collector using a CFD Fluent Solar Load Model. In: MATEC Web Conferences 13, pp. 1–5
Al-Obaidi, K.M., Ismail, M., Abdul Rahman, A.M., 2014. A Study of the Impact of Environmental Loads That Penetrate a Passive Skylight Roofing System in Malaysian Buildings. Frontiers of Architectural Research, Volume 3(2), pp. 178–191
ASHRAE, 2013. ASHRAE/ANSI Standard 55-2013 Thermal Environmental Conditions for Human Occupancy. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Atlanta, GA, USA
Azhari, A.W., Sopian, K., Zaharim, A., Al Ghoul, M., 2008. A New Approach for Predicting Solar Radiation in Tropical Environment using Satellite Images – Case Study of Malaysia. WSEAS Transactions on Environment and Development, Volume 4(4), pp. 373–378
Baharun, A., 2002. Envelope Retrofitting for Energy Efficiency in Malaysian Building using DTM’s. PhD Thesis, University of Leeds, Leeds, United Kingdom
Baskaran, A., 2002. Dynamic Wind Testing of Commercial Roofing Systems. National Research Council of Canada, Ottawa, Canada
Ciampi, M., Leccese, F., Tuoni, G., 2005. Energy Analysis of Ventilated and Microventilated Roofs. Solar Energy, Volume 79(2), pp. 183–192
Endriukaityte, A., Monstvilas, E., Bliudzius, R., 2005. The Impact of Climate Parameters on Air Movement in Ventilated Roofs Air Gap. Vilnius Gediminas Technical University, Vilnius, Lithuania
Heiselberg, P., Bjørn, E., Nielsen, P.V., 2001. Impact of Open Windows on Room Air Flow and Thermal Comfort. International Journal of Ventilation, Volume 1(2), pp. 91–100
Ibrahim, S.H., 2004. Thermal Comfort in Modern Low-income Housing in Malaysia. PhD Thesis, University of Leeds, Leeds, United Kingdom
Ibrahim, S.H., Azhari, N.A., Nawi, M.N.M., Baharun, A., Affandi, R., 2014a. Study on the Effect of the Roof Opening on the Temperature Underneath. International Journal of Applied Engineering Research, Volume 9(23), pp. 20099–20110
Ibrahim, S.H., Baharun, A., Nawi, M.N.M., Junaidi, E., 2014b. Analytical Studies on Levels of Thermal Comfort in Typical Low-income Houses Design. Unimas e-Journal of Civil Engineering, Volume 5(1), pp. 28–33
Ismail, M., Malek, A., Rahman, A., 2012. Stack Ventilation Strategies in Architectural Context: A Brief Review of Historical Development, Current Trends and Future Possibilities. International Journal of Research and Reviews in Applied Sciences, Volume 11(2), pp. 291–301
Kamaruzzaman, S.N., Razali, A., Zawawi, E.M.A., Basir, S.A., Riley, M., 2018. Residents' Satisfaction Towards the Indoor Environmental Quality of Re-engineered Affordable Housing Scheme in Malaysia. International Journal of Technology, Volume 9(3), pp. 501–512
Linshuang, L., Hong, Y., 2016. The Roles of Thermal Insulation and Heat Storage in the Energy Performance of the Wall Materials: A Simulation Study. Scientific reports, Volume 6(24181), pp. 1–9
Lysaght, 2014. Installation Guide. Available Online at , Accessed on February 5, 2015
Malaysia Meteorological Department, 2014. General Climate of Malaysia. Available Online at , Accessed on August 14, 2016
Qasim, S.M., Fadhel, A.A., Ahmed, A.A.S., 2010. Experimental and Theoretical Investigation of Composite Materials as Thermal Insulation for Resident Building. Journal Engineering Development, Volume 14(3), 105–123
Rajeh, S., 1994. Wind Ventilation of Terrace Housing in Malaysia. In: ISI-UTM International Convention and Exposition, January 24–26, Kuala Lumpur, Malaysia
Raut, S.P., Mandavgane, S.A., Ralegaonkar, R.V., 2014. Application of Small-scale Experimental Models for Thermal Comfort Assessment of Sustainable Building Materials. International Journal of Civil Engineering, Volume 12(4), pp. 441–446
Roslan, Q., Ibrahim, S.H., Affandi, R., Mohd Nawi, M.N., Baharun, A., 2016. A Literature Review on the Improvement Strategies of Passive Design for the Roofing System of the Modern House in a Hot and Humid Climate Region. Frontiers of Architectural Research, Volume 5(1), pp. 126–133
Tinker, J.A., Ibrahim, S.H., Ghisi, E., 2004. Thermal Comfort in Typical Modern Low-income Housing in Malaysia. In: Proceeding of International Conference on Exterior Envelope of Whole Building IX, Clearwater Bridge, FL, USA
Trinuruk, P., Sorapipatana, C., Chenvidhya, D., 2007. Effects of Air Gap Spacing between a Photovoltaic Panel and Building Envelope on Electricity Generation and Heat Gains through a Building. Asian Energy Environment, Volume 8(1), pp. 73–95
US Department of Energy, 2011. Attics: Ventilation. Energy Efficiency and Renewable Energy. Gill Martin, New Orleans, LA, USA