Efficacy of Energy Conservation Measures and Building Energy Intensity of a Multi-Building Complex in Malaysia

. As Malaysia continues to develop at a fast pace, the number of buildings in this country rapidly increases. Commercial buildings which include office buildings are one of the three major energy consuming sectors, which includes industrial and transportation sectors. Most Malaysian government office buildings tend to consume energy inefficiently due to lack of energy optimization. This study aims to analyse the energy performance as well as the factors that influence energy consumption in government office buildings. The chosen buildings for this case study are six government office buildings located in Kuala Lumpur, the capital of Malaysia. In this study, literature review has been conducted on the common factors affecting energy consumption in office buildings. The energy consumption data of the buildings were collected and analysed by comparison among the buildings and the SketchUp software. The Building Energy Intensity (BEI) of each building was also calculated using the formula in MS 1525:2019. Literature review and results from the case study show that air-conditioning system is the major energy consumer in office buildings, followed by lighting system while other office equipment consumed the least energy. The findings also highlight that energy consumption in office buildings is affected by non-design factors such as building occupants’ behaviour, number of building occupants, outdoor temperature as well as passive design factors such as building orientation and window-to-wall ratio. Recommendations were derived based on the findings from literature review and the case study for best practices to optimize energy consumption in government office buildings in Malaysia.


Introduction
The built environment consists of 36% of the world's total energy consumption [20]. Generally, Malaysian buildings consume 48% of the energy generated in the country while commercial buildings use up to 38,645 gigawatts hours (GWh). Increase in the number of buildings in Malaysia may indicate national progress. However, this has also increased energy demand [8]. The energy sources in Malaysia depend heavily on fossil fuels [8]. In Malaysia, coal made up 50.6% of the fossil fuels combusted to generate electricity in 2017 [15].
Alongside energy demand, construction of office buildings is among the vast developing sectors in the industry [16]. Building energy usage is one of the three main energy-consuming industries, the other two being the industrial and transportation industries. Malaysian government office buildings tend to consume energy inefficiently due to lack of energy optimization which leads to high energy demand [12]. The factors influencing high energy consumption in office buildings are needed to be determined in this study. Generally, the energy consumption of a typical office building is affected by non-design factors which are related to occupants' behaviour, climate, building function, and passive design factors such as building orientation, window design, and building façade colour. Noranai [22] stated that one of the reasons for the high energy * Corresponding author: hayati@um.edu.my usage is the lack of awareness on energy savings from the building owners and building users. Besides, office buildings use energy within the maintenance and operation stage such as operating elevators, office appliances and heating, ventilation, and air-conditioning (HVAC) system. [12] Based on the MS1525:2019 standard, the ideal building energy intensity for new buildings in is 200 kWh/m²/year. In 2007, typical office buildings in Malaysia have the BEI of 220 to 300 kWh/m²/year [6]. Chan [3] also proved that most Malaysian office buildings have the BEI of 200 to 250 kWh/m²/year in 2008. In a case study conducted by Tahir [13] on the BEI of government office buildings in 2017 showed that their BEIs exceeded 200 kWh/m²/year. Comparing the findings from the study conducted in 2007 and 2017, it is seen that the energy performance of government office buildings did not improve over the years. The Malaysian government has put in effort in producing sustainable plans towards reaching the goals in initiatives on green government building for newly developed as well as existing buildings. The Green Technology Policy (GTP) introduced in 2009 has the vision for Malaysian buildings to comply with every green design feature that leads to energy performance while accomplishing building users' comfort. The Public Works Department Malaysia had also put in effort to promote sustainability in building sectors via its sustainable practices and guidelines formulation [21]. For instance, the Public Works Department Malaysia introduced the Penarafan Hijau JKR (pHJKR) in 2015 that serves as a guideline for development of sustainable buildings. However, Ohueri [14] found that even in green buildings, actual operational energy consumption is different with the predicted measurements because of occupants' behavioural incongruities.
Other than the immediate need to speed up the development of sustainable buildings, energy auditing practice on the existing non-green buildings is also needed to allow applicable and economical retrofit [19]. Much research had been carried out on the performance of green buildings on fulfilling the guidelines such as the Green Building Index. However, there is lack of study conducted on the energy consumption of non-green office buildings that has inadequate sustainable practice especially in energy usage. Previous studies shown that most of the energy consumption validation works using building energy modelling were carried out towards unrealistic cases under specific range of conditions such as outdoor temperature, humidity, air-velocity, etc. Factors like human behaviour was not taken into considerations in the energy simulations [8]. Comprehensive research on the breakdown of energy usage and recommendations for energy saving measures in Malaysian government office buildings is needed. As such, practical, realistic, and sustainable energy consumption practice can be derived and implemented.

Building energy audit
An energy audit is a systematic approach to review and investigate the current energy usage [12]. According to the guidelines established by the Energy Commission Malaysia, the three methods that are commonly applied in energy auditing are benchmarking, preliminary audit, and general audit. Implementation of benchmarking consumption is primarily carried out by comparing the measured consumption to other similar office buildings [13].
In energy audit, the Building Energy Index (BEI) is studied. Building Energy Index is defined as "the ratio between annual energy consumption of a building (kwh/year) and nett floor area of the building" [5].

Energy consumption in office buildings
Generally, office buildings consume the most energy during the operation and maintenance stage. Chan [3] stated that a typical Malaysian office building uses approximately 250 kWh/m 2 of energy per year. The consumption is broken down into around 64% for air conditioning; 12% for lighting; and 24% for general equipment. A study on energy consumption in Malaysian office buildings done by Saidur [17] stated that air conditioners are the main energy users consuming 57% of the energy in office buildings, followed by lighting at 19%, lifts and pumps at 18%, and other equipment which uses 6%. Similarly, Tahir [12] found that air-conditioning system consumed the most energy at 51%, followed by lighting system (34%), plug load at 8% while other office appliances at 7% in his study on three Malaysian government office buildings.
The factors contributing to energy consumption in buildings are categorized into two which are non-design factors and passive design factors.

Occupants' behaviour
Building occupants' behaviour can significantly influence the building energy consumption. A study conducted by Masoso [11] on six randomly selected commercial buildings in South Africa showed that energy wastage in office buildings is due to building users' behavioural problems. In Masoso's case study building, the air-conditioning system starts operating at 3:00 a.m. but the workers only occupy the building at 7:30 a.m. The air-conditioning system switches off at 10:00 p.m. but the occupants leave the building at 4:30 p.m. Computers and lights were also left on after the occupants leave the building [11].

Cooling load of the building
The amount of air-conditioning load is dependent on the air temperature needed to be maintained in the building [3]. Different zones in a building can have different cooling load. For example, in office buildings, the cooling load for fully packed meeting rooms will be higher than loosely occupied open space office.

Climate and outdoor temperature
The climate in Malaysia is consistent throughout the year. Referring to the Malaysian Meteorological Department [10], the climate in Malaysia has uniform temperature, high humidity, and plentiful rainfall. The wind speed in Malaysia is generally light and the average sunshine is 12 hours which is from 7 a.m. to 7 p.m. [13]. As building acts as a barrier between outdoor temperature and indoor temperature, climate variables such as solar radiation and outdoor air temperature also affect the space cooling and heating requirements [3]. Malaysia is a tropical country that has average outdoor temperature at 27°C [8]. The indoor temperature should be within the range of 24qC to 26qC for the occupants to feel comfortable with reference to MS 1525: 2019. [5]

Passive design factors
Passive design factors are related to the building design such as building orientation, window systems and the size and shape of buildings. For example, if most of the building windows are facing East and West, the solar heat gain of the building will be high and can lead to higher cooling load.

Building envelope materials
The choice of building envelope materials is crucial as it can affect the energy consumption significantly. As the building ages, the building envelope will deteriorate. This means that heat will escape through the cracks in walls, single-paned windows, etc. It will also lead to increase in cooling load as energy tends to escape through poor building envelope [18]. In the research done by Chan [3], the indoor climate and electricity usage of a building can be influenced by different building envelope characteristics such as insulation, wall colour, window-to-wall ratio, etc.

Building façade colour
The façade colour can affect the thermal performance of a building. Azamejad [2] confirmed that the surface temperature of dark-coloured wall can reach up to 54°C during the mid-day. The cooling demand for a building increase when dark façade is used [9]. Hence, choice of lighter colour for a building façade can help to reduce energy consumption as it does not absorb as much heat as dark façade.

Window design
Window-To-Wall (WWR) ratio is also crucial in energy consumption of a building. The window-to-wall ratio (WWR) is calculated by dividing the total area of the window openings by the total exterior wall area at the building elevation. Energy consumption can be reduced by 10% if daylighting strategies can be implemented in the building [4]. In a study conducted by Al-Ashwal [1], he found that small WWR (5-10%) and glazing with high visible transmittance can lead to highest decrease in energy consumption. Malaysia receives six hours of sunshine per day with a daily solar radiation that ranges from 14.90 MJ/m 2 to 22 MJ/m 2 on mean average [8].
The location, size, shape, and orientation of windows in a building will cause significant effect on solar gains and heat gains of a building. It will also affect the lighting demand in the building [3]. Hence, it is essential to design windows to block out direct sunlight and to allow natural ventilation as well as maximize daylight in the building to reduce energy usage.

Overall thermal transfer value (OTTV)
The overall thermal transfer value (OTTV) is the measure of heat gain into the building via the building envelope. It can act as an index to evaluate the thermal performance of a building. In calculation of OTTV, it is assumed that the building envelope is entirely enclosed and does not consider the internal shading device such as curtains and blinds, solar reflection or shading from neighbouring buildings as well as green walls. According to MS1525:2019 [5], the OTTV for the building envelope should not exceed 50 W/m 2 . OTTV is the sum of heat conduction through the walls, heat conduction through the windows and solar heat gain through the windows.
Where, WWR is the window-to-gross-exterior wall area ratio for the orientation under consideration; ∝ is the solar absorptivity of the opaque wall; Uw is the thermal transmittance of opaque wall (W/m 2 K); Uf is the thermal transmittance of fenestration system (W/m 2 K); OF is the solar orientation factor; and SC is the effective shading coefficient of the fenestration system; whereby Solar Heat Gain Coefficient (SHGC) = SC x 0.87.

Roofing system
In Malaysia, a typical terraced house gets most of its solar gain from the roof. Planning and layout of spaces in a building can affect lighting and air-conditioning requirements. Grouping and interaction of building spaces, ceiling height and space volume as well as buffer zones in the roofing system will affect the energy demand in buildings significantly [3].

Methodology
This study investigated the factors affecting energy consumption in office buildings through literature review. Then, a remote energy auditing on the case study buildings was carried out due to the Movement Control Order (MCO). The energy consumption data of the case study buildings were collected. The Building Energy Intensity (BEI) of each case study building was calculated by using the formula suggested in MS1525:2019 to analyse the energy performance of the buildings. Energy consumption of the case study buildings and the factors affecting energy consumption were discussed. Based on the data analysis, recommendations on the best practices that can be implemented in government office buildings to optimize energy consumption were put forward.

Case study buildings
In this research, the analysis on energy consumption was conducted on six government office buildings which are A, B, C, D, E and F Block. The details of the case study buildings are shown in Table 1. Based on Table 2, F Block is the largest office building with nett floor area. All the buildings were constructed with brick walls and equipped with shading devices. Overall, all the six case study buildings consume energy for air-conditioning system, lighting system, and office equipment. Only F Block has a lift system. The case study buildings use electricity mainly supplied by the Tenaga Nasional Berhad (TNB) at 99%, solar energy generated from Grid-Connected Photovoltaic (GCPV) System which is installed in B Block and distributed directly to A, B and F Block at 0.87% and Diesel Set Generator at 0.07%. Table 1. Details of the case study building.

Location
Kuala Lumpur

Building Type
Commercial Building

Building Function Office Building
Year built 1979

Energy consumption of each block
The energy consumption for each case study building was analysed by collecting the monthly energy consumption information. The duration for the collected energy consumption data was January to December of 2019 and 2020. Based on the monthly energy consumption of the case study buildings, the energy consumption (kWh) of the six buildings was steady throughout 2019. However, the energy consumption in April 2020 was drastically low because of the Movement Control Order (MCO) and the building occupants were not allowed to go to the office. The energy consumption of the case study buildings in 2019 was higher than 2020 except for E Block that had significant higher energy consumption in 2020 than 2019 as shown in Table 3.
Referring to  As shown in Fig. 1, the BEI of all the case study buildings fulfilled the BEI benchmark of 200 kWh/m 2 /year stated in MS1525:2019. They fulfilled the BEI benchmark of 150 kWh/m 2 /year as required for GBI rating except for E Block.

Energy consumption by system
The energy consumed by air-conditioning system was the highest at 65.5%, lighting system at 22.6% while other appliances consumed a total of 11.9% of the total energy consumption as shown in Fig. 2.  Fig. 1. BEI of each case study building.

Discussions
The energy consumption of the case study buildings can be considered excellent as the BEI of each of the blocks fulfilled most of the energy benchmark. The factors influencing the energy consumption of the case study buildings are categorized into non-design factors and passive design factors.

Occupancy and operating duration
Based on the monthly energy consumption analysis of the case study buildings, the energy consumption of the six buildings was consistent in 2019 as the buildings were occupied throughout the year. However, there was a significant drop in energy consumption in April 2020 as Movement Control Order (MCO) were enforced to curb the spread the Covid-19 virus and building occupants were not allowed to return to office. Hence, it is proven that duration of occupancy and operation days will affect the energy consumption of buildings.
The number of building occupants can also affect the energy consumption of buildings. F Block recorded the highest energy consumption among the other case study buildings as it accommodated the most occupants at 687 occupants as referred to Table 2. F Block comprises individual office rooms and open space office area that are constantly occupied by occupants during the operational hours. Hence, the energy demand for F Block will be higher than other blocks. Furthermore, occupants' activity will also significantly influence the energy demand. The E Block recorded the highest BEI among the case study buildings at 183.12 kWh/m2/year. Although E Block had the lowest constant occupants, it consists of large area of cafeteria, meeting rooms and activity rooms that will be intermittently occupied by many people from other blocks.

Energy efficiency of office equipment
The plug load for the case study buildings were mainly used for office equipment such as desktop computers, printers, photocopy machine, etc. The equipment needs to be energy-efficient and equipped with energy saving features to minimize energy usage.

Outdoor temperature
For the case study buildings, the outdoor temperature was 31°C to 33°C. High outdoor temperature will cause the building occupants to increase the usage of airconditioning system to achieve indoor thermal comfort.

Building orientation
Building orientation is one of the main factors for energy consumption as it affects the cooling load of the building. The building windows that are facing east and west will increase solar heat gain. Good building orientation can minimize the heat gain of the building and reduce energy consumption for air-conditioning and lighting. According to Table 5, the building orientation of the A Block, C Block, D Block and F Block are all facing towards the direction of north-east. B Block faces towards north while E Block faces towards north-west. For A, B, C, D Blocks, there are no windows at the West and East elevation. E and F Block have less windows at the West and East elevation as well. This has effectively reduced the solar heat gain through the windows into the building. E Block which has the main façade facing north-west has the highest BEI as it has high solar heat gain. A and B Block which have their main façade facing north records lower BEI due to lower solar heat gain. Furthermore, the main façade of the case study buildings does not face the solar radiation directly. However, E Block has more building façade surface that is facing towards north-east which is directly exposed to sunlight.

Window-to-wall ratio (WWR)
As shown in Table 5 towards north and south than the building elevation that faces towards west and east. The high WWR in the building elevation that faces towards north and south maximizes the entry of daylight to the building to reduce the usage of artificial lightings. Fewer windows are placed at the building elevation facing towards the west and the east.

Overall thermal transfer value (OTTV)
With reference to Table 5, the overall thermal transfer value (OTTV) of the case study buildings facing northeast orientation was significantly higher as the solar radiant from the east orientation was the greatest. High OTTV indicates the greater heat gain of the building envelope, and this can impact the cooling load for the building. According to MS1525:2019, the ideal OTTV of the building envelope should not exceed 50 W/m 2 . All case study buildings do not fulfil this criterion. The case study buildings were completed before MS 1525:2019 was introduced. A Block recorded the highest OTTV due to the high window-to-wall ratio of the A Block compared to other blocks. This proves the direct relationship between window-to-wall ratio and the heat gain of the building.

Building façade colour
According to MS1525:2019, external wall with darker colour has higher solar absorptivity. Hence, building façade with light colour has lesser heat gain compared to dark colour façade and this leads to lesser energy consumption. All the case study building has light colour façade.

Recommendations for pre-construction phase government office buildings
For newly developed office buildings, energy efficient designs are significant to ensure ideal energy performance of government office buildings. As discussed earlier, energy consumption of a building is highly dependent on passive design factors such as building orientation, window-to-wall ratio, and façade colour. The ideal building orientation is north or south which can avoid solar heat gain as it does not face the sunlight directly. The wind direction is also important as it affects the cooling load of the building. Furthermore, light colour should be applied on building façade to reduce heat absorption through the building walls. During the design stage, the building windows should be placed at the side that face towards north or south to maximize daylight entering the building while avoiding solar heat gain. Windows that has higher Visible Light Transmittance allows more daylight to enter the room. In short, usage of clear glazing can promote energy savings as the lighting load can be reduced. Although clear glass allows maximum daylight to enter the space, the solar heat gain of clear glass can be high. Hence, the window glazing needs to be designed specifically to allow high level of visible light while still control solar heat gain. Choosing lowemissivity glass (Low-E glass) as the window glazing can minimize the amount of infrared and ultraviolet light as well as heat from direct sunlight to pass through the glass without reducing the amount of natural light that enters the room. Low-E glass windows come with a microscopically transparent thin coating to reduce the emissivity of glass surfaces and reflect heat. Thus, Low-E glass reflects short and wave infrared ray and only allow visible light that has short wavelength to pass through it.

Occupants' behaviour
Occupant's behaviour can alter the building energy consumption significantly. The awareness on energy saving must be raised among the building occupants to avoid energy wastage. Signages can be pasted next to the switches and plugs to remind them to switch off the appliances when not in use. As office appliances are mainly controlled by the occupants, they should be aware to turn off these appliances when not in use. The office equipment can be labelled to indicate which equipment can be switched off and which are necessary to remain switched on. Usage of appliance with 4-or 5star rating by the Energy Commission Malaysia or energy star-label can enhance energy optimization.

Air-conditioning system control
More energy can be saved by raising the thermostat temperature of the air-conditioning system. The ideal indoor design conditions of an air-conditioned space to be designed and maintained with the dry-bulb temperature of 24°C to 26°C, which is recommended by the Energy Commission Malaysia. Alternative off-hour controls shall be provided in zones like storeroom, file storage room and photocopying room to prevent energy wastage.

Motion sensors
Motion sensors can detect motions and provide automatic lighting control for a building. Motion sensors will turn off the lights of the room when there are no occupants in the room. This provides a low-maintenance way to reduce energy usage in the government office buildings. Motion sensors can be installed in spaces that are intermittently occupied such as toilets, corridors, staircase area, lift lobby, storeroom etc.

Daylight harvesting
Daylight harvesting is making use of natural light to reduce the usage of artificial lighting. Daylight harvesting in rooms is estimated to provide energy savings of 20 to 60% while ensuring the occupants receive adequate amount of light in the space. Daylight sensors can provide comfort and convenience to the occupants as it maintains the adequate light level for a space while consuming lesser energy. Malaysia has an average daylight of 12 hours a day. Hence, daylight harvesting can significantly contribute to energy savings in government office buildings.

Routine maintenance and replacement
Regular maintenance of the building systems can avoid breakdown and wastage of energy. As building system equipment such as chillers and pumps can be faulty after long-term usage, it is ideal to replace them. Besides, it is estimated that adequately maintained ACMV system consumes 15% to 20% lesser energy than an undermaintained system.

High-cost energy saving recommendations
To prove that the application of reflective window films can significantly reduce the cooling load in office buildings, the Overall Thermal Transfer Value (OTTV) of one of the case study buildings, A Block, before and after application of reflective films was calculated. A Block has the highest OTTV among the other case study buildings. The proposed reflective window films have the thermal properties of U value: 5.11 W/m 2 K, shading coefficient: 0.29, solar reflectance: 0.27 and visible transmittance: 0.14. [7] Table 6 shows that the OTTV of A Block is significantly lower than the existing OTTV after the proposed application of reflective window film.

Conclusion
Energy consumption in government office buildings can be affected by non-design factors which include building occupants' behaviour, occupants' activity, climate, and space function. Passive design factors include size and shape of the building, building orientation, window systems, etc. The findings from the case study have also supported the findings from literature review. A typical government office building spends most energy on the air-conditioning system, followed by lighting system and the least energy is used on other equipment such as lifts and office appliances. The monthly energy consumption of the case study buildings was analysed and compared. It was found out that air-conditioning system consumed the most energy, followed by lighting system while other office appliances consumed the least energy. Hence, this matches the findings from literature review. All case study buildings have good energy performance as their Building Energy Index (BEI) did not exceed the benchmark of MS1525:2019. To optimize energy savings in government office buildings, it is crucial to have energy efficient design at the development stage with good building orientation to avoid extensive solar heat gain from the windows and building façade. It is important for the government office buildings to practice energy saving measures such as creating awareness in energy saving among the building occupants, routine maintenance of building equipment, and retrofitting existing fluorescent lights to LED lights. The thermal performance of existing windows of the government office buildings can be improved by applying tinted or reflective films. It is proven that the OTTV of office buildings can be significantly reduced after applying window films.
As there are practical energy saving measures to be implemented in government office buildings, the government office buildings will be on the track on being more sustainable in their energy consumption.