COMPARISON OF ENERGY PERFORMANCE OF TWO GENERIC RESIDENTIAL BUILDINGS FROM NORTH CYPRUS

COMPARISON OF ENERGY PERFORMANCE OF TWO GENERIC RESIDENTIAL BUILDINGS FROM NORTH CYPRUS Murat Özdenefe, Jonathan Dewsbury School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M13 9PL, UK. Corresponding author: e-mail: murat.ozdenefe@postgrad.manchester.ac.uk REFERENCE NO Ref # 9-16 Keywords: Energy performance; Buildings; Simulation; Thermal loads; North Cyprus ABSTRACT The major amount of the recently constructed buildings in North Cyprus is residential buildings. Almost all of these buildings employ reinforced concrete and blocks as construction material. Also 87 % of the all existing residential buildings are made up from either reinforced concrete with block walls or load bearing block walls. Most of these buildings do not have any insulation application. This increases energy consumption of the buildings. In this work energy performance of two typical residential buildings from North Cyprus investigated. Their insulated and uninsulated energy performances are compared. It is found that substantial decrease could be achieved in their heating and cooling energy consumptions if a polystyrene insulation is applied. 1. INTRODUCTION According to the population and housing unit census carried out in 2006 in North Cyprus (N. Cyprus), 77 % of the residential buildings are made up from reinforced concrete and blocks (perforated clay bricks, lightweight concrete blocks, stones ). In these buildings reinforced concrete is employed for the frame of the constructions whereas blocks are employed for the nonbearing wall constructions. 10 % of the residential buildings are made up from only load bearing walls with various blocks. So, totally 87 % of the residential buildings are made up from either reinforced concrete and blocks or load-bearing walls with blocks [1]. Thermal performance of buildings made up from reinforced concrete and blocks can be improved by applying effective insulation during the construction stage. However, in N. Cyprus insulation is rarely applied to the buildings and this causes poor thermal comfort in the built environment as well as increased energy consumption for heating and cooling. The objective of this work is to simulate and compare the thermal loads as well as annual energy performance of two residential buildings (referred to as building 1 and building 2) from N. Cyprus under the local weather conditions. 2. METHODOLOGY Two generic residential buildings from N. Cyprus are selected for this work. This selection is based on the analysis of the building statistics of N. Cyprus which explained in detail in subsequent sections. The buildings have similar construction frames (reinforced concrete) however; their nonbearing wall and roof constructions are made up from different materials and configurations. There is not any insulation application on the walls and on the roofs of the buildings. Firstly the heating and cooling loads as well as the annual energy consumptions of the buildings are calculated for their original constructions. Subsequently it is assumed that insulation is applied to the external walls of the buildings. Then heating and cooling loads as well as the annual energy consumptions of the buildings having the insulated external walls are evaluated. The effect of the insulated external walls to the thermal loads and energy consumptions has been investigated. Due to the external walls of the buildings have different materials and configurations the comparison of their loads and energy consumptions would mislead us. Therefore another simulation 10th International Conference on Clean Energy (ICCE-2010) Famagusta, N. Cyprus, September 15-17, 2010

is done by assuming that the buildings have the same external wall materials and configurations in order to make a sensible comparison of their loads and energy performances. A building simulation program called IES Virtual Environment (VE) is utilized for the evaluation of the loads and annual energy performance of the buildings. 3. GEOGRAPHICAL FEATURES AND CLIMATE OF CYPRUS Cyprus is the third largest island in the Mediterranean Sea having 9851 km 2 area [2]. It is located at 35 o North latitude and 33 o East longitude. The island is situated at the eastern part of the Mediterranean Sea and has distance of 65 km from Turkey, 95 km from Syria, 350 km from Egypt and 750 km from Greece. There are two major mountain ranges on the island. The Kyrenia Mountains lie on the northern cost of the island and extents 150 km distance in east-west direction. The Trodos Mountains, which are situated on the southern part of the island, has the highest peak on the island that is 1951 m above the sea level. The Trodos Mountains range 120 km distance in eastwest direction. Between these two mountain rows, Mesarya Plain spans [3]. Cyprus has an intense Mediterranean climate with hot and dry summers from mid-may to mid- September and rainy cool winters from November to mid-march. There are short period of autumn and spring seasons having rapid changeable weather conditions between the summer and winter seasons. The clear sky and the high sunshine amount create considerable seasonal and daily temperature differences. The seasonal temperature differences between the mid-summer and midwinter are 18 o C and 14 o C respectively for inland and coasts. Difference between the day maximum and night minimum temperatures is significantly large especially at inland part of the island during summer. These differences are 16 o C for inland and 9 to 12 o C for the other parts of the island during summer. These values decrease to 8 to 10 o C for lowlands and 5 to 6 o C for the mountains in winter. In July and August mean daily temperatures are 22 o C and 29 o C for the Trodos Mountains and central plain respectively. Average maximum temperatures for these months reach up to 36 o C. In January the mean daily temperatures decrease to 10 o C and 3 o C for central plane and for the higher parts of the Trodos Mountains respectively [4]. 4. BUILDINGS OF N. CYPRUS Building construction sector occupies a significant portion of N.Cyprus economy. Parallel to the increase in the population during recent years, the demand for new housing increased and boosted the new building constructions. The building statistical data in N. Cyprus is collected compiled and published by the State Planning Organization Statistics and Research Department since 1980. The data in this work is compiled from the latest publication of the State Planning Organization Statistics and Research Department. The building construction statistics involves the data about the building constructions that have been finished or have received the final approval in 2007. The building constructions statistics of 2008 and 2009 are still being processed for publication by the State Planning Organization Statistics and Research Department [5]. Building constructions in N. Cyprus are classified according to various categories. These categories are Residential, Industrial and Commercial building constructions. The buildings that do not fall in any of these categories are collected under the name of miscellaneous building constructions. Residential building constructions involve the apartment buildings and single houses, semidetached houses as well as row houses whereas; the industrial building constructions involve the factories and warehouses. The commercial building constructions are composed of retail buildings, offices and entertainment buildings (restaurants, bungalows, nightclubs, cafes, hotels) as well as garages (for car parking). On the other hand, the buildings that fall in the miscellaneous

category are cellars, dormitories, garages, pergolas, subsidiary buildings, sport facility buildings and agricultural buildings. Total floor areas of the buildings and their percentage shares that are constructed or have received final approval in the year 2007 are given in Fig. 1. The State Planning Organization Statistics and Research Department also classifies the buildings according to their structural systems and masonry work. According to the statistical data, reinforced concrete is employed for the frame of the constructions in all of the buildings whereas for the walls of the all buildings blocks (perforated clay bricks and lightweight concrete blocks) are used [5]. When the figures given in Fig. 1 are investigated, it is seen that the residential buildings dominate the buildings that are constructed or have received final approval in 2007 with the share of 75 %. Therefore, residential building constructions should be investigated in more detail. The residential buildings are divided in two categories; houses and apartments. A house is a building which is intended for residential use with one or two dwelling units regardless the number of stories, whereas an apartment is also intended for residential use with regardless of number of stories but with three or more dwelling units. Total floor areas of the residential buildings (houses and apartments) and their percentage shares for the year 2007 are given in Fig. 2. It is seen that the percentage shares of the total floor areas of the houses apartment buildings that are constructed or have received final approval in 2007 are very close to each other [5]. Miscellaneous, 59485 m^2, 9% Commercial Buildings, 71914 m^2, 11% Industrial Buildings, 30719 m^2, 5% Residential Buildings, 466951 m^2, 75% Fig. 1: Floor areas of buildings in m 2 and their percentage shares based on building categories for the year 2007. Houses, 229367 m^2, 49% Apartments, 237584 m^2, 51% Fig. 2: Total floor areas and percentage shares of the houses and apartments for the year 2007.

Although the above figures give detailed information about the recently constructed residential buildings, it would be valuable to look to data about all the residential buildings that exist in N. Cyprus. According to the population and housing census carried out in 2006 there are 72624 residential buildings in N. Cyprus which 76 % of them are houses and 22 % of them are apartments (the rest 2 % are either subsidiary or other types of buildings). It was stated that all the buildings and so all the residential buildings constructed in 2007 employed reinforced concrete for the frame of the constructions and various blocks for the walls. However this is not the case for all the existing residential buildings. The ratio of the reinforced concrete frame residential buildings with walls made up with various blocks is 77 % of the all existing buildings. This is followed by the adobe buildings and buildings with load bearing walls with various blocks, with the ratios of 13 % and 10 % respectively [1]. 5. SELECTED BUILDINGS FOR SIMULATION Buildings for simulation are selected based on the data given in the preceding section. It is thought that the selected buildings would represent typical buildings from N. Cyprus. When the figures given in section 4 are investigated it is seen that typical buildings of N. Cyprus are residential buildings which made from reinforced concrete and blocks. Therefore, two generic residential buildings made from reinforced concrete and blocks have been selected for simulation. Both of the buildings are single-family detached houses and located on the costal regions of the island. Building 1 has two storey; ground floor and 1 st floor. Ground floor consists of an anteroom, a living room, dining room and a study room as well as a kitchen and a toilet. 1 st floor includes three bedrooms, two bathrooms and a corridor. The building floor area is 210 m 2. Front façade of the building faces to the north direction. Reinforced concrete and brick are the major construction materials employed in building 1. The frame of the building is reinforced concrete whereas the walls are made up from horizontally perforated clay bricks. Walls are double wall system that is composed of 5 cm of air gap between two 10 cm layer of perforated bricks and 2.5 cm of cement plaster on external and internal surfaces. Grade level floor and upper floor is reinforced concrete. Travertine marble is employed as flooring material. The roof is composed of pitched wooden roof, which stands on a reinforced concrete slab. There is an attic between the slab and pitched wooden roof. Tiles are employed on the external surface of the wooden roof. The windows are double glazed with white coloured PVC frames. Building 2 has three storey; ground floor, 1 st floor and 2 nd floor. In the ground floor, there is an anteroom, a living room, a gallery, a kitchen, a toilet and a little cellar. In the 1 st floor there are two bedrooms, a room, a bathroom and a corridor. There is only a bedroom in the 2 nd floor. The building floor area is 170 m 2. The front façade of the building 2 is looking to the south-west direction. The frame of the building 2 is reinforced concrete whereas the walls are composed of three layers; 20 cm of bimsblock blocks and 2.5 cm of cement plaster on the internal and external surfaces. Grade level floor and upper floors are reinforced concrete. Granite marble is used as flooring material. The building roof is reinforced concrete slab. Windows are double glazed with PVC frames. The pictures of buildings can be seen in Fig. 3. The U values (thermal transmittance) of the various elements of building envelope for building 1 and building 2 are given in Table 1.

Fig. 3: Building 1 (left hand side) and building 2. Table 1. U values of the various elements of building envelope of building 1 and building 2. U value (W/m 2 K) Building 1 Building 2 External wall 1.1290 0.6869 Grade level floor 1.7360 1.9166 Flat roof -------- 3.4959 Pitched roof 2.9282 -------- Window 1.9773 1.9773 Door 2.1944 2.1944 6. SIMULATIONS WITH IES VE For the simulation, the building simulation software IES VE is utilized. This software is a product of Integrated Environmental Solutions (IES) Ltd., which is a company that develops software simulation tools and gives consulting services for architects and engineers for development and management of sustainable buildings. The IES VE is a set of applications linked by Common User Interface (CUI) and a single Integrated Data Model (IDM). This enables to use a data input of an application by the others within the software. The IES VE includes modules such as; ModelIT which is the application used to input the building geometry, ApacheSim which is for thermal simulation, Radiance which is for lighting simulation and SunCast which is the module for solar shading simulation [6]. Before calculating the loads and simulating the annual energy consumption of the buildings various processes has been carried out by using different modules of the IES VE. First, geometrical models of building 1 and building 2 are created by using the ModelIT module of the IES VE. The models of the building 1 and building 2 are referred to as model 1 and model 2 respectively. The geometrical models can be seen in Fig. 4. This process is followed by assignation of the thermal properties of the construction materials by utilizing ApacheSim module of the software. Subsequently APLocate which is the whether and site location editor is used for assigning the design and simulation weather data to the models. Design and simulation weather data files for Cyprus exist in APLocate module of the IES VE. These are found and assigned to model 1 and model 2. The outdoor design temperatures for Cyprus according to these weather data files are 5 o C and 34.8 o C for winter and summer respectively. 20 o C and 24 o C values are entered as the indoor design temperature values for winter and summer respectively. The simulation weather data includes the hourly data for the various weather parameters such as dry-bulb temperature, wet-bulb temperature,

solar radiation, wind speed etc. Design weather data is used for heating and cooling load calculations whereas simulation weather data is used for annual energy consumption calculations. After carrying out the processes mentioned above, heating and cooling loads as well as the annual energy consumptions of the buildings are evaluated. Firstly the simulations are done for the models with their original construction materials. Subsequently their external walls are altered by applying 5 cm polystyrene insulation material (k=0.029 W/mK) to outer surface of the walls. Then the simulations are carried out for the models with the altered walls. Afterwards the minimum U valued wall construction is selected and applied to both of the models and simulations are carried out. This is done in order to compare the performance of the two models. The U values of the original and altered walls are given in Table 2. The original wall constructions are referred to as wall 1 and wall 2 whereas the altered wall constructions are called as wall 3 and wall 4 for model 1 and model 2 respectively. As it is seen in Table 2 wall 4 has the minimum U value so it is selected for application to the both of the models for energy comparisons. Fig. 4: Model 1 (left hand side) and model 2. Table 2. U values of the original and altered walls. U value (W/m 2 K) Wall 1 1.1290 Wall 2 0.6869 Wall 3 0.3832 Wall 4 0.3145 7. RESULTS AND DISCUSSION The results of the simulations are given in the tables below. The results for the model 1 with the wall 1 and wall 3 are given in Table 3. The percentage reductions in the loads and energy consumptions by the application of wall 3 to the model 1 are given in Table 4. It is seen that substantial reduction is achieved in the loads and energy consumptions by the application of wall 3. The simulation results for model 2 are given in Table 5, whereas the percentage reductions in the loads and energy consumptions by the application of wall 4 to the model 2 are given in Table 6. It is seen in Table 6 that there is significant reductions in heating load and heating energy consumption however; the reductions in the cooling load and cooling energy consumption are very small compared with the heating load and heating energy consumption values. It is seen that the percentage reductions in loads and energy consumptions for model 2 is smaller than model 1. This is due to the difference in U value reductions when the polystyrene insulation is applied. Wall 3 which is the altered wall for

model 1 has almost 3 folds of reduction in the U value however wall 4 which is the altered wall for model 2 has around 2 fold of reduction in the U value. It is also seen that the percentage reductions in the heating loads and heating energy consumptions are greater than percentage reductions in the cooling load and cooling energy consumptions. Altering the U values of the walls only decreases transmission heat gains and heat losses. However, the substantial portion of the cooling load and cooling energy consumption results from the solar gains through transparent windows. Therefore it is normal to have greater reductions for heating loads and heating energy consumptions. Table 3. Simulation results of model1. Heating Cooling Wall 1 Wall 3 Wall 1 Wall 3 Plant load (kw) 13.1 10.8 9.9 8.7 Plant load per unit floor area (W/m 2 ) 62.5 51.4 47.3 41.7 Annual energy cons. (MWh) 15.6 11.9 14.3 12.7 Annual energy cons. per unit floor area (kwh/m 2 ) 74.4 57.0 68.3 60.8 Table 4. Percentage reduction in the loads and energy consumptions by the application of wall 3 to the model 1. Heating Cooling Percentage reduction in Plant Load (%) 18 12 Percentage reduction in annual energy cons. (%) 23 11 Table 5. Simulation results of model2. Heating Cooling Wall 2 Wall 4 Wall 2 Wall 4 Plant load (kw) 11.6 10.4 10.3 9.8 Plant load per unit floor area (W/m 2 ) 68.0 61.5 60.6 57.9 Annual energy cons. (MWh) 9.2 7.6 19.0 18.6 Annual energy cons. per unit floor area (kwh/m 2 ) 54.2 44.5 112.0 109.4 Table 6. Percentage reduction in the loads and energy consumptions by the application of wall 4 to the model 2. Heating Cooling Percentage reduction in Plant Load (%) 10 4 Percentage reduction in annual energy cons. (%) 18 2 The wall construction that has the minimum U value is the wall 4. Therefore wall 4 is applied to both of the models and a simulation is carried out. The simulation results for the models with wall 4 are given in Table 7. Due to the floor areas of the buildings are different from each other the results based on per unit floor area are also evaluated. The comparison of the two buildings is done based on the per unit floor area results. It is seen in Table 7 that the heating and cooling loads per unit floor area are greater for model 2. Model 1 has 18 and 28 % lower heating and cooling load per unit floor area than model 2. If we look to the annual energy consumptions per unit floor area it is seen that model 2 has less consumption for heating however, it has much greater consumption for cooling. The annual heating energy consumption per floor area of model 2 is 20 % less than the consumption of model 2. On the other hand annual cooling energy consumption per floor area of

model 1 is 45 % less than the value of model 2. The main reason for this drastic difference in annual cooling energy consumption per floor area is the difference in the fenestration areas between model 1 and model 2. Total fenestration area of model 2 accounts 19 % of its total external surface area (external wall area + fenestration area). This value is 13 % for the model 1. Due to the significant portion of the cooling energy caused by the solar gains, existence of bigger fenestration areas especially transparent windows increases the cooling energy. To reveal the effect of transparent windows another simulation is carried out by employing external shutters which prevents the solar gains through the transparent windows. When the external shutters applied to the models and the simulation is carried out the cooling loads per floor area reduces to 28.6 and 33.2 W/m 2 for model 1 and model 2 respectively. These values are very close to each other. The percentage difference between the cooling loads per floor area of model 1 and model 2 reduces from 28 % to 14 % with the external shutter applications. Also substantial reduction achieved for the annual cooling energy consumption per floor areas. With the external shutters the annual cooling energy per floor area becomes 33.9 and 43.6 kwh/m 2 for model 1 and model 2 respectively. It is seen that the percentage difference between the annual cooling energy per floor area of model 1 and model 2 reduces from 45 % to 22 % with the external shutter applications. It is seen that applying the same walls and shutters does not eliminate all the differences in loads and energy consumptions between model 1 and model 2. One reason for this discrepancy is due to the dissimilar roof constructions of model 1 and model 2. The orientations of the models are also different. Furthermore there might be some local reasons such as effects of nearby buildings or plantation etc. In order to reveal the reasons of the rest of the differences in loads and energy consumptions between model 1 and model 2 a detailed room by room and surface by surface heat loss and heat gain analysis should be carried out. Table 7. Simulation results of model 1 and model 2 with the wall 4. Heating Cooling Model 1 Model 2 Model 1 Model 2 Plant load (kw) 10.6 10.4 8.7 9.8 Plant load per unit floor area (W/m 2 ) 50.3 61.5 41.4 57.9 Annual energy cons. (MWh) 11.6 7.6 12.6 18.6 Annual energy cons. per unit floor area (kwh/m 2 ) 55.4 44.5 60.2 109.4 References [1] TRNC Prime Ministry, TRNC Prime Ministry State Planning Organization Population and Housing Census, [Online] http://nufussayimi.devplan.org/kesin-sonuc-index_en.html, 2007. [2] Bilge Isik and Tugsad Tulbentci, Sustainable housing in island conditions using Alker-gypsumstabilized earth: A case study from northern Cyprus, Building and Environment, Vol. 43, No. 9, 2008, pp.1426-1432. [3] Nazife Ozay, A comparative study of climatically responsive house design at various periods of Northern Cyprus architecture, Building and Environment, Vol. 40, No. 6, 2005, pp.841-852. [4] Meteorological Service of Cyprus, Climate of Cyprus, [Online] http://www.moa.gov.cy/moa/ms/ms.nsf/dmlcyclimate_en/dmlcyclimate_en?opendocument [5] State Planning Organization Statistics and Research Department, Turkish Republic of Northern Cyprus Building Construction and Parcel Statistics 2007, TRNC State Printing Office, 2009. [6] IES Virtual Environment, VE User Guide Virtual Environment 5.9, Integrated Environmental Solutions Limited, 2009.