Optimum Insulation Material and Thickness in the External Walls and Determination of the Energy saving cost in Hospital: Case Study in Malaysia S. MOGHIMI a, B.J. RAATJES b, P.M.VAN MOORSEL b, F.AZIZPOUR a, S.MAT a, C.H.LIM a & K. SOPIAN a a: Solar Energy Research Institute, Universiti Kebangsaan Malaysia, 436,Bangi, Selangor. MALAYSIA. (tel:+63-89216646, e-mail: k.sopian@eng.ukm.my) b: School of Architecture, Build Environment and Civil Engineering, Hanze University, Groningen, THE NETHERLANDS Abstract: - Selection of insulation material and determination of its optimum thickness is one of the prime solutions at energy efficiency in retrofitting projects. In this study for calculating energy consumption, proposed building was modeled in IESVE (Integrated Environmental Solutions<Virtual Environment>) software and energy consumption for different insulation material and variety of their thickness was simulated. To find the optimum thickness and material, net saving cost over different lifetime periods was calculated. Polystyrene and mineral wool are two kinds of common and available insulations that were selected as the material options. According to the results mineral wool is a better material than polystyrene for external wall insulation and also it is found that the optimum thickness of mineral wool over 5, 1 and 2 year lifetimes are 4 cm, 8 cm and 1 cm respectively. Key-Words: -wall insulation, optimum insulation thickness, energy cost savings, retrofitting 1 Introduction In order to increasing fuel price, growing scarcity of fossil fuels and also intensification of CO2 emission in environment the demand of energy efficient building is increasing seriously. In other hand due to growing the global demand of energy, energy efficiency of buildings is needed for safeguarding energy resources for next generations. Hospital is a 24 hours a day and 365 days in a year operation and it is a unique building because of its intense demand for energy. Malaysia is a country located in hot-humid region where cooling is one of the biggest energy consumption aspects, in buildings including hospitals. In a hospital building where cooling demands are continuous throughout or 24 hours in a day, the benefits of energy saving are even greater than (e.g.) an office building, where cooling demand is intermittent. In a typical hospital, 45% of the energy cost at bills is due to the HVAC system. [1] The thermal performance of insulation is highly influential on hospitals energy demand. According to [2] M.S. Mohsen et al (21), the insulation of external walls and roofs can increase energy saving up to 77%. By increasing energy efficiency strategies, monthly energy cost can be decreased significantly. Furthermore, they cause the reduction in CO2 emission from power plants [3] The main objectives of this study are as below: A) To investigate the thermal performance of two common wall insulations by simulating in IESVE software. B) To investigate the optimum insulation material and its thickness. C) To calculate energy saving cost per square meter of gross area over different lifetime and thickness. ISBN: 978-1-6184-122-7 138
Advances in Environment, Biotechnology and Biomedicine ceiling tile for ceiling and clay roof tiles for roof material. Fig. 2 illustrates the view of modelled building. 2 Methodology 2.1 Field study description The Universiti Kebangsaan Malaysia (UKM), Faculty of Medicine was started in 1972. In 1997 Hospital UKM was established as a teaching Hospital (HUKM) located in Cheras, Selangor [4]. Malaysia is a tropical country with hot-humid climate which lies in between 1º and 7º north and 1º and 12º east. [5] The facility department is the three story building in HUKM where is selected for this study. This building is located in west part of HUKM. Fig. 1 taken from Google earth, illustrates the general view of HUKM and facility department. Fig. 2: Modeled building in IESVE. The input data include building construction materials, local climate data which is taken from ASHRAE standard, number of occupancy, internal load, HVAC system data, lighting data, equipment data, etc.[6] As it shown in Table 2 external walls in selected zone are constructed with two layers of plaster and one layer of brick. Table 2: Material of external walls. material thickness Fig. 1: General view of HUKM and Facility department. Out side to Inside 2.2 Field study modelling in software The modelled building consists of 3 levels and has a completely air-conditioned floor area. Table 1 shows the specification of this building. Table 1: Specification of facility department. NO Floor 1 Zones name Basement Physiotherapy plaster 13 mm Brick 114 mm plaster 13 mm At this study polystyrene and mineral wool are selected as insulation materials at 2, 4, 6, 8 and 1cm thickness. Table 3 shows the characteristic of insulation materials which are put in software. Area 1871 M2 356 2 M material Conductivity w/(m.k) Density kg/m3 Specific heat capacity j/(kg.k) 187 M2 polystyrene Mineral wool.4.35 25 3 138 1 Table 3: Insulation material characteristic. 2 3 Ground Lobby-catering floor area-kindergarten First floor Office-praying room The modelled building is of standard construction with concrete for structure, bricks for external walls, ISBN: 978-1-6184-122-7 For finding optimum of insulation thickness, the influence of different insulation thickness on total 139
energy saving cost and net energy saving cost over three life times period is studied. Energy rate per kwh is calculated from dividing total annual energy cost in RM to total annual energy consumption in kwh. Energy saving cost is the residuum between energy cost beforee and after using insulation in lifetime period. Annual energy cost over the life time is calculated By Eq.1. [7] Energy saving (RM) 12 1 8 6 4 Eq.1. 2,2 Insulation thickness total energy saving net saving in 5 years,4,6,8,1 Where C E is the energy cost in RM/kwh and E is total annual energy consumption in kwh and g is inflation ratio in percentage. The equation for total insulation cost (Eq. 2) and net energy cost saving (Eq.3) defined as: C ins =C i. A f.x ins Eq.2 NS=(C TEun -C TEins )-C ins Eq.3 Where C ins is the total cost of insulation and C i is the cost of insulation in RM per m 3 and A f is the total insulated area in external walls in m 2 and X ins is the insulation thickness and NS is net energy cost saving in RM. In each life time periods, the optimumm thickness is the maximum amount of net saving in different insulation thickness. It means during that period of time it has a maximum payback. Furthermore, the comparison between polystyrene and mineral wool has been conducted over each lifetime period. Hence the optimumm thickness and material of insulation has been determined according to the net saving energy cost. 3 Result and discussion 3.1 Net saving value over 5 years Fig. 3 shows the trend lines of total energy saving cost, and net saving value calculated for polystyrene. Fig. 3: Net energy cost saving over 5 years for Polystyrene. As Fig. 3 illustrates the net saving value is scaling up when the thickness of insulation is increasing up to 6 cm, therefore over 5 years lifetime period the maximum value of net energy cost saving is at 6 cm thickness. As it shown in Table 3 by installing Polystyrene with 6 cm thickness, 4.1 $ per square meter of gross floor areaa is saved over 5 years. Fig. 4 shows the net saving value for mineral wool in different thicknesses. As Fig. 4 Shows, the maximum value of net saving cost is at 4 cm thickness or according to Table 4 is equal to 4.14 $/m 2. Cost - Malysian Ringgit (RM) 14 12 1 8 6 4 2 total saving net saving in 5 years,2,4,6,8,1 Insulation thickness Fig. 4: Net energy cost saving over 5 years for mineral wool. ISBN: 978-1-6184-122-7 14
By comparison between fig. 3 and Fig. 4 it is concluded that in 5 year lifetime period the optimum insulation and thickness is mineral wool with 4 cm thickness. 3.2 Net saving value over 1 years As it is shown in Fig. 5 net energy cost saving trend line reaches to the maximum in 8 cm thickness of insulation. According to Table 3 the total net saving value is 26185 RM, or 1.86 $/m 2. Fig. 6 shows the net saving value for mineral wool in different thickness Over 1 year lifetime, the maximum value of net saving is in 8 cm thickness with 2978 RM saving cost value or 11.4 $/m 2. Cost - Malaysian Ringgit (RM) 3 25 2 15 1 5,2,4,6,8,1 total energy saving net saving in 1 years Fig. 5: Net saving cost in 1 year for polystyrene The comparison of results shows that mineral wool with 8 cm thickness is optimum in 1 year lifetime. 3-Net saving value over 2 year The same calculations were done over 2 year lifetime for both material-polystyrene and mineral wool- the results are shown in Fig. 7 and Fig. 8 respectively. The maximum value of net saving cost in both materials is in 1 cm thickness. Cost - Malaysian Ringgit (RM) 7 6 5 4 3 2 1,2,4,6,8,1 total energy saving net saving in 2 years Fig. 7: Net saving cost over 2 years lifetime for polystyrene 7 Cost Malaysian Ringgit (RM) 3 25 2 15 1 5 total saving net saving in 1 years Cost - Malaysian Ringgit (RM) 6 5 4 3 2 1 Electrical saving cost net saving in 2 years,2,4,6,8,1,2,4,6,8,1 Fig. 6: Net saving cost over 1 years lifetime for mineral wool Fig. 8: Net saving cost over 2 years life time for mineral wool. ISBN: 978-1-6184-122-7 141
As it is shown in Table 4 the maximum net saving cost is 586678 RM or 3.9 $/m 2. Therefore, mineral wool with 1 cm thickness is the optimum insulation for external walls. Table 3: Net saving cost over different period of lifetime and different insulation thickness for Polystyrene. lifetime Insulation thickness 2 cm 4cm 6cm 8cm 1cm Net saving cost Net saving cost Net saving cost Net saving cost Net saving cost RM $/m2 RM $/m2 RM $/m2 RM $/m2 RM $/m2 5 years 64715 3.41 7593 4. 76134 4.1 72323 3.81 66567 3.51 1 years 154918 8.16 191185 1.7 23164 1.7 26185 1.86 24893 1.79 2 years 398187 2.97 5288 26.44 545752 28.74 567195 29.87 577944 3.44. Table 4: Net saving cost over different period of lifetime and different insulation thickness for mineral wool. Insulation thickness 2 cm 4cm 6cm 8cm 1cm Net saving cost net saving cost net saving cost net saving cost net saving cost RM $/m2 RM $/m2 RM $/m2 RM $/m2 RM $/m2 lifetime 5 years 68612 3.61 78556 4.14 77747 4.9 7393 3.85 66629 3.51 1 years 1641 8.64 197974 1.43 2813 1.96 2978 11.4 2731 1.92 2 years 42129 22.19 5233 27.39 559659 29.48 578144 3.45 586678 3.9 4 Conclusions The optimum thickness of insulation and net saving in 5, 1, 2 years lifetime are calculated in both mineral wool and polystyrene in a hospital in Malaysia. The results show that: 1- By increasing the life time period the optimum thickness of insulation grows up. 2- Mineral wool is the optimum material for insulating external wall in this study. 3-the maximum value of net saving energy cost in 5, 1 and 2 years lifetime are 78556 RM,2978 RM and 586678 RM, respectively,in other wise 4.14 $/m 2,11.4$/m 2 and3.9$/m 2. ISBN: 978-1-6184-122-7 142
References: [1] Commercial Building Performance Healthcare Facilities Consortium for Energy Efficiency, Inc.25 [2] M.S. Mohsen, B.A. Akash. Some prospect of energy savings in buildings. Energy Conversion and Management 42 (21) 137 1315 [3] Kemal C omakl, Bedri Y uksel. Environmental impact of thermal insulation thickness in buildings. Applied Thermal Engineering 24 (24) 933 94 [4] Universti Kebangsaan Malaysia Website, www.ukm.my [5] Nastaran Makaremi, Elias Salleh, Mohammad Zaky Jaafar, AmirHosein Ghaffarian Hoseini. Thermal Comfort Conditions of Shaded Outdoor Spaces in Hot and Humid Climate of Malaysia. Building and environment, 211, doi: 1.116/j. buildenv.211.7.24 [6] Ashfaque Ahmed Chowdhury, M.G. Rasul, M.M.K.Khan. Thermal-comfort analysis and simulation for various low-energy cooling technologies applied to an office building in a subtropical climate. Applied Energy 85 (28) 449 462 [7] Aynur Ucar, Figen Balo. Determination of the energy savings and the optimum insulation thickness in the four different insulated exterior walls. Renewable Energy 35 (21) 88 94 ISBN: 978-1-6184-122-7 143