Energy retrofit strategies for housing sector in the arid climate

Accepted Manuscript Title: Energy Retrofit Strategies for Housing Sector in the Arid Climate Author: Fadi AlFaris Adel Juaidi Francisco Manzano-Agugliaro PII: DOI: Reference:

S0378-7788(16)30816-7 http://dx.doi.org/doi:10.1016/j.enbuild.2016.09.016 ENB 7005

To appear in:

ENB

Received date: Revised date: Accepted date:

23-5-2016 6-9-2016 9-9-2016

Please cite this article as: Fadi AlFaris, Adel Juaidi, Francisco Manzano-Agugliaro, Energy Retrofit Strategies for Housing Sector in the Arid Climate, Energy and Buildings http://dx.doi.org/10.1016/j.enbuild.2016.09.016 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Energy Retrofit Strategies for Housing Sector in the Arid Climate

Fadi AlFaris1, Adel Juaidi1, Francisco Manzano-Agugliaro 1, *

1 Department of Engineering, University of Almeria, CEIA3, Almería, 04120, Spain

*Corresponding author. Tel.:+34 950015346; Fax: +34950015491. E-mail address: [email protected]

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Highlights     

A practical case study for 10 villas in arid climate (UAE) has been discussed. The results of new energy conservation measures for existing housing sector have been assessed, implemented and monitored. The energy performance improvement achieved was 25.1% in average according to actual field measurements. Each villa has different reaction against the energy savings opportunities based upon several factors. The achieved energy savings were varied from 14.4 to 47.6%.

Abstract This paper discusses sustainable strategies have been implemented to improve the energy performance for the housing sector in arid climate, especially villas. A practical case study along with field measurements is presented in order to highlight the behavior of the energy performance after implementing energy conservation measures in practice. The residential sector in arid climate especially in Gulf Countries has a significant share of carbon emissions. Millions of householders occupy villas and town houses. The harsh hot weather of this region is one of the reasons for a high demand on the cooling energy and the electricity consumption in the housing sector. Thus, there is a real potential to retrofit the existing houses with practical energy conservation measures. These techniques are affordable and feasible economically. Also, they play a substantial role to increase the energy efficiency of the residential units on the demand side. This study discusses the results of 12 months were monitored after implementation of energy savings measures on selected 10 villas in the capital of UAE- Abu Dhabi. This research highlights different responses by each villa against the implemented energy savings opportunities. The target of these executed strategies is to improve the energy performance of these selected villas after conducting a detailed energy assessment and implementing its recommendations. A detailed analysis of the electricity performance of the baseline and the monitoring period has been performed by using the actual readings of the existing power meters according to the international performance measurement and verification protocol. This research presents the energy data for the entire year before and after the implementation of the energy conservation measures - ECMs. These ECMs show the potential of improvement of energy performance in the housing sector by increasing the energy efficiency by 25.1% in average through low and medium cost techniques. The percentage of savings varies from 14.4% to 47.6% of the total electricity according to the individual operating conditions for each villa and the behavior of occupants. As a result, they contribute reducing the carbon and GHG emissions, and open new perspectives of energy savings for housing sector in arid climates. 2

Keywords: Energy Performance, Energy Conservation Measures, Housing Sector, Retrofit strategies, Arid Climate, UAE. Nomenclature FAHU: Fresh Air Handling Unit ECM: Energy Conservation Measure ESCO: Energy Service Company EUI: Energy Use Index GHG: Green House Gases IPCC: Intergovernmental Panel on Climate Change IPMVP: International Performance Measurement and Verification Protocol LED: Light Emitting Diode LEED: Leadership in Energy and Environmental Design. M&V: Measurement and Verification NASA: National Aeronautics and Space Administration UAE: United Arab Emirates

1. Introduction Energy is a continuous driving force for economic development, social advancement, and improved quality of life [1]. Human health and thermal comfort have been recognized as the most significant parameters during the evaluations of indoor environment [2, 3]. There has been renewed interest in energy efficiency improvement methods compared to only a few years ago when energy was relatively inexpensive and abundant [4]. The shortage of resources and environmental issues caused by human activities encourage designers and policy makers to search for energy saving strategies and policies for sustainable development [5, 6]. Cleaner energy strategies practices serve to reduce demand for energy [7] and other environmental resources [8]. However, with rapid growth of the population in the Gulf Countries because of the high development of economy, the demand of energy increased substantially. And consequently, 3

the carbon dioxide emissions, in this region and especially in UAE, achieved one of the highest records in the world per capita [9]. The buildings (residential and commercial clusters) consume about 15% of total energy consumption in the country, whereas the industrial sector share reaches to 63% and the transportation percentage is 22% of the annual energy consumption [9]. The residential part has a significant contribution of the carbon emission and the energy use. This sector has recorded the largest impact on the energy demand growth in a city like Al-Ain by 45.9% [10]. UAE population now is about 9 million, up from 3 million in 2000. However, the growth of population is greater than 14% per year. Thus, it is expected to reach in excess of 12.5 million by 2030 [10]. Therefore, the energy consumption by residential sector will be increased drastically and its energy demand will proportionally rise to higher levels [11]. Compared to Europe, the residential sector contributes in 26% of the annual energy consumption [12]. On the world level, the residential buildings consume 10% with about 1.5% increasing rate per year [13]. Also, the trend of the global greenhouse gases emissions will increase from 2005 to 2050 by 52% [14]. The growth in population will increase the dwelling units that may cause to increase the greenhouse gases (GHG). The GHG emissions by residential buildings during the operational stage influence negatively on the global warming. This will require generating more cooling energy to compensate the global warming problem for the indoor environment. These massive quantities of cooling energy will exacerbate this challenge of climate change and warm up the earth and so on [15-18]. Thus, the need to take serious steps and measures toward sustainability and energy management is urgent and necessary. Accordingly, European commission has launched a new initiative to control the fund and investment in energy efficiency solutions for the residential and commercial buildings [13]. Besides, USA was one of the earliest countries to adopt a high standard and regulation for residential sector’s energy efficiency. Alongside with USA, others countries such as; UK, France, Canada, Germany, China, Japan and South Korea have implemented energy efficiency programs and measures aggressively, whereas Spain didn’t implement effectively these regulations although it has a conservative standard launched at a very early stage. Recently, countries like Mexico, Russia, Australia, New Zealand, Italy and South Africa, have showed substantial results by enforcing the implementation of the energy efficiency measures [19-24]. Intergovernmental Panel on Climate Change (IPCC) has supported the concentration on improvement of energy efficiency of the building sector. It has identified that the most cost effective measures that return the benefits in a short time is the building cluster across several sectors [25]. A high growth of the villas construction in UAE has observed. For instance, in Dubai the houses number increased from 20,000 in 2000 to 60,000 houses in 2009 [26]. Therefore, profound measures have been adopted for the new and existing buildings. In Dubai in 2013 a new green building code has been launched for the new development. Whereas, in Abu Dhabi “ESTIDAMA” rating system (it is a green building standard) became a mandatory for all new villas, governmental and commercial building. For the existing buildings; the retrofitting industry to improve the energy performance of different type of facilities has been launched by 4

Dubai government through energy service companies’ regulation. This regulation aims to reduce the energy consumption by 30% by 2030. Besides, Dubai has announced a new energy regulation to support the use of renewable energy in the residential sectors and especially in the villas. These policies support the sustainability movement and the trend of using the clean energy to reduce the carbon emissions. These strategies are the first steps to shift from fossil fuel to renewable energy [10, 27]. In addition to these policies and programs, voluntary green building rating systems are used by several end users in UAE. These assessment schemes assists to optimize the energy performance such as; Leadership in Energy and Environmental Design (LEED) for new construction, existing buildings, homes, neighborhoods and other buildings types [28]. However, this paper will concentrate on the retrofitting industry for the villas. It will discuss how to optimize the energy performance in the houses in UAE by using affordable energy conservation measures. However, in UAE the energy cost is subsidized by the government except in emirate of Dubai. Hence, the householders in the other emirates are not much motivated to invest on new energy savings opportunities. However, this mindset might be changes if an incentive scheme by the government is developed or the electricity tariff increases, which is likely to happen gradually. The continuous reduction of oil prices globally will play a key factor in order to take this important decision [29]. Nevertheless, this research discusses several energy conservation measures that are affordable by the householder and feasible economically under the current circumstances in UAE. A practical case study has been executed in 10 selected villas in UAE. These villas have been monitored for 12 consecutive months starting from August 2014 and ending by July 2015. A detailed site survey and studies have been conducted for these villas as a sample. Then, only the low and medium cost energy savings measures were implemented. These measures performance were measured to verify the savings over one year. The electricity was compared in monthly basis between the baseline (the reference year- one year before) and the reporting year- one year after. It is undoubtedly that these proposed scenarios of energy management programs by the governments will improve the energy performance of the buildings, and consequently will reduce the carbon emission. However, the people always look at the quick win opportunities and the short term solutions. Thus, this study highlights holistic energy efficiency solutions for the villas that any householder may adopt as a one package. Also, it provides an input to the researchers about which areas might be improved in the houses and the gaps to be rectified. In the future, the scholars may have a deep insight on these energy systems separately to improve their efficiency. Several researches have discussed different strategies to reduce the energy consumption such as; increasing the efficiency of the houses’ appliances [30] improving the thermal insulation, active ventilation [31] and passive ventilation [32, 33] double glazing, shading coefficient [34] and roof coating [35]. These measures have been discussed separately in those studies. However, it hasn’t 5

been found a study that is combined the impact of implementing several energy conservation measures for the housing sector on the energy performance in the region. This paper addresses various energy savings opportunities and their influence on the energy behavior for each villa. These implemented energy efficiency strategies are affordable and feasible economically. This research measured the actual savings that have been achieved and monitored for 12 months by implementing several conservation measures together in a practical way. The purpose of this paper is to improve the performance of villas sector in UAE, by reducing the consumption of energy without compromising the comfort and the standards.

2. Factors Impacting the Energy Performance in the Existing Housing Sector Most of the current regulations concentrate on the new buildings, some research are related to the life-cycle energy use of prefabricated components, this follows the strategy for improving the productivity of prefabricated construction [36]. However, these solutions are not usual, and new developments are based in conventional constructions that represented between 0.5 and 2% of the total built facilities depending on the region and the economic growth [37, 38]. And hence, the assessment method of the energy performance of these new buildings is performed against the standards and regulations during the design stage. The analysis of building energy efficiency policies in light of improvements in energy performance is made by very populated countries as China [39], and the contributions of the construction industry to greenhouse gas (GHG) emissions are studied in detail [40]. However, two key factors influence the energy performance for the studied villas. These factors are 1) the bio-climate characteristics of the zone during the year, and 2) the initial conditions and buildings basic information of the villas such as buildings envelop, orientation and overhangs. These factors are very important to be considered when analyzing the energy performance. 2.1 Bio-climate characteristics However, the weather conditions has a substantial influence on the indoor environment, the building envelop design and consequently the energy demand response. In the major UAE cities, the climate is very hot and humid. As a coastal desert area that lies on (24° 28' N, 54° 22' E), Abu Dhabi has a harsh climate characteristics. It is a high temperature and very low rain fall rate due to its geographical location within the subtropical high pressure belt. Only four months are within the human climate comfort level; November, December, February and March [33]. However, January is the coldest month as the mean temperatures drop to 18.8°C. In these five months, the air conditioning systems are not required in the villas since the cooling is not required. Generally, the mean annual temperature is higher than 27.6°C and in summer the dry bulb temperature exceeds 40°C in July and August [33]. Also, the average wind speed is between 3.2 to 4m/s from the northwest direction as specified in table 1. 6

Table 1 shows the source of Abu Dhabi weather data by RETscreen software. The RETScreen Climate Database includes the meteorological data from ground monitoring stations and/or from NASA's global satellite/analysis data. If climate data is not available from a specific ground monitoring station, data is then provided from NASA's satellite/analysis data. As outlined in figures 1 and 2 the sunrise and suset times along with the sun path are presented over time in Abu dhabi. As shown in figure b the x axis refer to months, while the y axis represents the hours per day. It shows that the dusk times vary from 17:40 in winter to 19:30 in summer, whereas the dawn times change between 5:15 in summer to 6:50 in winter for the emirate. For the solat path diagram as shown in figure 2, the elevation angles of the sun along with the azimuth angles are plotted for all the months. It illustrates that sunrise from east north (azimuth = 78°) at 6am. While, sunset happen at 18:41 when at 278° west north. The climate charactarastics have been considered in analysing the energy prformance. They provide a detailed insight about the behaviour of the new energy conservation measures over time.

2.2 Houses information and Initial conditions There are several models for the houses in arid climate as UAE since 1970s till now. Most of these houses especially those were built before Dubai Decree 66-2003 and ESTIDAMA rating system 2010 have a poor thermal insulation [41-43]. Therefore, the building envelope is the first key factor impacting on the energy performance of the constructed villas [44, 45], and especially in this climatic zone [46]. The building orientation, thermal insulation of the roof, walls and windows, glazing specifications such as solar heat gain coefficient and light transmittance, and air tightness of the building are important parameters that differentiate the energy performance of the houses. In such a harsh climate in UAE, a high cooling demand is needed. Hence, if these factors are not designed in a conservative approach at the design stage to comply with the regulations, the energy performance of these villas will be inefficient and energy wastes would be massive. Especially, the cooling load in UAE represents 60% of the consumed electricity in the buildings [47]. The efficient materials and performance of the building envelope play significant role to reduce the cooling demand [48]. Accordingly, figure 3 outlines the audited villas details as a sample. Detailed architectural design and drawings of the villa have been provided. The building orientation, envelope, overhangs and elevations have been studied before taking into consideration the recommended energy efficiency measures and applicable strategies. A sample of a villa’s drawings shows that terraces and overhangs were constructed to provide a proper shade for the eastern and southern exposures. This condition will reduce the solar gain and accordingly the cooling energy for the thermal zones for the directions of east and south. However, the existing transparent glass of the 7

western windows is not shaded, therefore, the solar gain are expected heavily for the western thermal zones in the villas. Accordingly, this gap has been addressed for each villa according to its real direction and building orientation. Thus, it is recommended for such retrofitting conditions to improve the glazing performance by installing a coating film for the transparent windows that exposed to the sun directly without a shade as explained in section 4. For the roof material of the villas’ envelope, it has been noticed that the black gravel material is used to cover the roof surface. This existing condition increases the heat absorption by the sun from the roof side. Accordingly, the cooling energy is required to compensate this heat gain from the roof during day and night times. Therefore, it is strongly recommended for such housing sector to install a cool roof system with a high reflective material. More details about the implementation of this energy conservation measure are explained in section 4.

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Data and Methodology

This paper discusses the stages that followed to evaluate the energy performance of residential houses and the strategies to improve the energy performance of selected villas in Abu Dhabi. This study has selected 10 villas to implement these techniques of energy efficiency through several stages as shown in Figure 4. A detailed energy performance assessment has been conducted for each villa with actual measurements. Furthermore, the existing energy systems were analyzed to evaluate their efficiency and the areas that should be improved. Then, an economic feasibility study has been performed for each energy conservation measure for the entire houses to examine the affordability and the return of investment by a simple payback period method. As a result, only the feasible energy savings’ strategies have been implemented on these 10 villas. The installation period was less than 2 months including the commissioning stage. And finally, the monitoring phase has been pursued to verify the energy savings for one whole year compared to the baseline that identified in an early stage of this study.

3.2 Energy Performance Assessment At this initiation stage a detailed energy assessment has been conducted for each villa. The main objectives of this assessment are to appraise the villas’ energy performance and then to propose the most feasible and applicable energy conservation measures. These measures were proposed for each individual villa according to the operating conditions per each villa. The energy performance evaluation was conducted for each building separately to inspect the systems, audit the performance and report the gaps and potential of savings. Also, at this stage, the energy consumption baseline was identified to measure the improvement. Then several surveys and site 8

visits have been conducted along with the actual measurements against it. Several parameters were measured in each villa such as; power, voltage, load profile, power factor, energy consumption, cooling energy, lighting power, luminance level, relative humidity, room temperature, supply air temperature and hot domestic water pressure. Moreover, various energy systems have been evaluated and analyzed to determine the major and minor electricity consumers and the energy balance. For instance; the lighting system consumes 12-18% of the total energy consumption; while, air conditioning and ventilation have the lion share of the energy consumption up to 70%. And the miscellaneous loads such as plug loads, home’s appliances and hot water contribute the balance of annual energy bills. This energy audit provided deep understanding of the existing villas’ systems and the operating circumstances. Additionally, other factors were taken into consideration in this assessment like weather conditions, number of family members, buildings’ orientation and the behavior of the occupants. Accordingly, several of Energy Conservation Measures (ECMs) were studied technically and analyzed economically to be affordable by average people. Only the most practical, reasonable and feasible strategies have been agreed for implementation. In order to proceed for implementation phase, a simple payback period of 3 to 4 year was acceptable indication for the approved and affordable energy conservation measure. According to the villas’ initial conditions, weather data of the city, site survey and the energy analysis, two areas of the buildings’ systems should be improved in terms of energy efficiency. This gap analysis highlights that improving the building envelope and considering new technologies of energy systems are important to increase the energy efficiency. For the building envelope, it has noticed that the solar gain is high from south and east direction. However, for the west direction the overhangs will play a significant role to mitigate this impact. Also, the gap of the doors and windows is visible that may increase the infiltration rate and accordingly waste the cooling energy. Besides, it has been noticed that the black gravels cover the roof space. This material has a low reflectance and emittance factors, which lead to a high solar heat absorption and accordingly high cooling energy to compensate such heat gain. All these gaps have been recorded and studied to provide the proper energy efficiency solutions for retrofitting industry. For the technology side, the existing equipment, lighting and air conditioning systems are not efficient and no regular maintenance work are implemented on the air conditioning systems. Additionally, the mode of operation is not related to the demand and actual needs. All these gaps increase significantly the losses of energy consumption. Therefore, they have been addressed to improve the energy performance as described in section 4.

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3.3 Implementation Skilled and experienced organization was involved for execution the approved energy conservation measures. These strategies have taken 2 months for implementation. The implemented energy conservation measures have been grouped into 2 categories; 1) Improvement of building’s envelope and, 2) Increasing the systems’ energy efficiency. After the installation, a testing and commissioning process has been performed to inspect the function of the upgraded energy system after villas’ makeover. Separate instantaneous measurements have been conducted to assure the performance and the power difference for each system. 3.4 Monitoring After the implementation of the energy savings strategies, the monitoring stage for 12 months has been commenced. This part of the study highlights the pursued techniques to verify the energy conservation measures. This stage ruled and regulated different variables and changes that occurred after the implementation stage that called reporting period. During the reporting period the energy consumption for each villa has been gathered and compared to the same month of the reference year. The reference year is the last 12 months before the implementation phase starting from August 2013 to July 2014. Other variables such as weather conditions, additional loads, number of occupants and days of occupancy have been monitored [49], calculated and accordingly the baseline adjusted. The standard used to monitor the achieved energy savings is the International Performance Measurement and Verification Protocol (IPMVP) Volume 1, EVO 10000 – 1:2012 [50]. The Measurement and Verification M&V demonstrates the avoided energy consumption and the improvement of the performance level rather than the total cost saved. In order to build a framework that finds the improvement of the energy systems, M&V plan is the key part to be developed at early stage to identify how the ECM performance would be evaluated. This gives a considerable degree of objectivity that will not be available if the savings are measured after the installation and commissioning [50]. By this approach, the electricity comparison between the years before and after and the savings calculation were developed to manage the baseline adjustment by identifying the static factors that influence on the savings calculation. Quarterly, 4 measurement and verification M&V reports were tackled in each quarter to monitor and evaluate the energy performance for each villa and entire project. Generally, IPMVP suggests four options to monitor achieved savings by the implemented energy conservation measures. These options are summarized as follows; Option A: Retrofit Isolation (Key Parameter Measurement): the achieved savings are calculated by a direct field measurement for only the key parameters of the energy conservation measure (ECM). However, the other related parameters are estimated.

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Option B: Retrofit Isolation (All Parameter Measurement): for this option, all the key parameters that related to the energy conservation measure (ECM) are measured in the field with no estimation. Option C: Whole facility: the energy savings are calculated based upon the main building meters readings. Therefore, the measurements are taken on the whole facility. Thus, this approach will need a regression analysis for the independent factors such as the cooling degree days. Option D: Calibrated simulation: the energy savings are determined according to the whole facility simulation. This simulation will model the actual measured energy consumption of the building. In this study, option C has been adopted and used. This option is the most convenient approach for the villas because several ECMs and strategy have been implemented. These ECMs influence on the whole facility/villa’s energy performance. Equation 1 shows the formula that used to calculate the savings as per option C. ES  BL  NRA  RPE

Eq. 1

Where; ES : The energy savings or the avoided energy use. BL : Adjusted electricity consumption (kWh) including the baseline energy considering the routine adjustment to reporting period conditions as shown in equation 2.

NRA : Non-routine Adjustment of the baseline to reporting period conditions.

RPE : Reporting period energy

The routine adjustments are calculated for electricity source by using mathematical models for the baseline based upon the independent variables. Therefore, the baseline electricity consumption data are adjusted according to Equation 2.

BL  C1 * x1  C2 * x2  A

Eq. 2

Where;

x1 = Cooling degree-days (°C); x 2 = Number of unoccupied days; A = Baseline Energy Consumption (kWh). 11

C1 And C 2 Coefficient of factors For non-routine adjustment, the baseline is adjusted in case of any change in operation such as; adding or removing equipment or even shutdown the villa. 4

Energy Conservation Measures

By retrofitting their homes to meet stricter energy efficiency standards, private homeowners can reduce home energy use significantly [51]. This paper examines the impact on the energy performance of villas by combination of several energy conservation measures. All the possible strategies that have less than 4 years as a payback period with an affordable capital cost were adopted for implementation. Therefore, different energy systems in the houses such as air conditioning, lighting, hot water and appliances have been targeted to evaluate their performance during the reporting period. Hence, in order to save the energy use in these villas, two areas have been improved as follows; 1) Building envelope; through improvement of the windows shading coefficient to reduce the solar heat gain [52], reducing the heat absorbed by the roof and improvement of the air leakage, 2) Systems’ efficiency: the major consumers such as air conditioning systems and lighting have been studied deeply to increase the operational efficiency by running the systems on demand and reducing the power of the lights without compromising the luminance level. Moreover, in a common practice, the conditions of these equipments should be maintained in a good status. Therefore, in order to increase their efficiency, maintenance works have been conducted. 4.2 Improvement of Building’s Envelope As outlined in the first section, the building envelope determines how the building would be affected by the climate conditions. The outdoor heat transfers from outside to inside occur through building envelope such as walls, roof and windows [53]. Furthermore, in order to reduce the required cooling energy to compensate this heat gain, efficient building envelope is needed to play this role. Heat gain that should be mitigated passes through the building envelope by conduction via external walls, windows and roofs, and by solar radiation through glass [54]. 4.2.1

Efficient Glazing Shading Coefficient

US Department of Energy estimates that one third of the cooling load comes from the windows by the solar heat gain [55]. That is because of inefficient glazing performance of the existing buildings’ windows. In Summer times, the improvement in the shading coefficient of the windows exposed to the sun without shading by overhangs in south, east and west directions is a persistent need. The solar gain has a high contribution to the cooling load for the indoor environment in UAE. Thus, the curtains are required to reduce the solar radiation. However, 12

curtain doesn’t allow enough daylight. Therefore, the clear windows in these studied villas are required to be replaced with new glass with a low solar heat gain factor. However, this measure would be expensive and not affordable by the owners, thus, it is recommended for such retrofitting project to install a window film that reduces the shading coefficient drastically with low investment as shown in Figure 5. The shading coefficient reduced from 0.9 to 0.21. The above solution costs approximately 2 times of the annual energy savings. This means that the simple payback period is about 2 years. 4.2.2

Roof coating

Recent years have seen an increase in the amount of green roofs in urban areas across the world [56], but this solution cannot be adopted in arid climates. Reflective materials are required in order to cool down the roof. Also, the solar reflectance of roof surface materials plays a key role to reduce the heat gain by reducing the roof temperature and reflect the sun heat away from the villas. The existing roof materials in these audited villas were black gravels as shown in Figure 6. These kinds of gravels absorb the heat and increase the heat gain accordingly. As a result of the analysis, In order to increase the solar reflectance, a special white coating material has been used to increase the solar reflectance factor. The roof surface temperature measured before and after the white coating is illustrated in Figure 7. The black gravel temperature was 71.4°C on July 2014 at 11:00 am reduced drastically after the white coating to 47.6°C. The above solution costs approximately 3.5 times of the annual energy savings. This means that the simple payback period is about 3.5 years.

4.2.3

Improving Air tightness

Air tightness is one of the key factors that taken into consideration during the design stage to reduce the waste of the cooling energy. The cooled indoor environment in the villas needs a low air exfiltration rates less than 5 air change per hour (ACH) at 50 Pascal according to International Energy Conservation Code 2012 [57]. Therefore, sealing gaps around doors and windows will improve the energy use and reduce the energy cooling wastes. Especially, it was noticed clearly the doors and windows were not tight enough to keep the cooling energy within the villa’s indoor boundary.

The above solution costs approximately 2 times of the annual energy savings. This means that the simple payback period is about 2 years.

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4.3 Increasing the Systems’ Energy Efficiency The construction year of the selected villas is 2009. Thus, the lighting and air conditioning have been specified and installed for more than seven years. Therefore, it is noticed that the technology is old and not efficient compared to the modern efficient systems. Also, the operating conditions of the equipment are not in the optimum level as specified by the manufacturer. Furthermore, several systems run without direct or indirect control. Accordingly, during the analysis, these systems were working in a low efficiency. Consequently, the energy conservation measures proposed and implemented were to upgrade the lighting lamps with new efficient LED lights, conducting maintenance work to assure that these systems are in efficient operating conditions and to improve the control system of the air conditioning to be working on demand. 4.3.1

Control the Air Conditioning Systems Based Upon the Demand.

Usual design practice is based on coping with extreme conditions, which normally leads to get oversized machines on all other occasions with milder weather. Typical air conditioning systems operate continuously until the room temperature is met. During this time, the compressor will run to generate a higher cooling power than air absorbs. This point will let the compressor continuing consuming power without any benefit. In order to avoid this operating point that called the saturation period, a controller with software that detects this condition has recommended to be installed. This controller will switch the compressor off during the saturation period to avoid the expected wastes and maximize the savings. In addition, the air conditioning system that installed currently in these villas is ducted split unit. Each of these units is controlled through a thermostat based on the room temperature. However, the set points of the room temperatures are set manually by the occupants. During the site survey, it was noticed for most of these thermostats were between 21ºC and 24ºC during the night and day times. Furthermore, in few villas these set points are set for whole the year, whether the villa occupied or not and in winter and summer. This kind of behavior varies between the villas’ householders. However, in order to make sure that the waste of energy would be reduced and these ducted split units will be performing according to the demand only, a programmable thermostat has been installed. This advanced programmable thermostat changes automatically the setpoint of the room temperature during the time and need according to unique circumstances for each villa. The setpoint is reset automatically at day and night times in winter and summer in economic and conservative way. This change doesn’t compromise the thermal comfort. The above solution costs approximately 1.5 times of the annual energy savings. This means that the simple payback period is about 1.5 years.

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4.3.2

Replacement of Conventional Lighting System with New Efficient Lights.

A lighting survey was conducted during the study period. It has been found that most of the installed lamps were in low efficiency. Therefore, it was recommended to replace these lights with new LED lamps having an efficacy of more than 80 lumen/Watt; 50% better than the existing lamps. Besides, this replacement will reduce the heat generated by the old lamps, and consequently will save the energy that is required for space cooling. The above solution costs approximately 2.5 times of the annual energy savings. This means that the simple payback period is about 2.5 years.

4.3.3

Improvement of the Air Conditioning Performance by Conducting Maintenance Works.

Continues and routine maintenance works improve the performance of the machines over time. Several studies showed that the regular maintenance works may save the air conditioning running costs by 5%, also, they will improve the thermal comfort and extend the life time of these systems [58]. Thus, it is found that no regular maintenance was performed in all the selected villas. Therefore, it was recommended to implement maintenance procedures in regular basis according to the manufacturer recommendations to increase the air conditioning split units’ efficiency. The above solution costs approximately 80% of the annual energy savings. This means that the simple payback period is about 0.8 year. 5 Results and Discussion After the implementation of the energy conservation measures ECMs, the energy performance has been monitored for each villa every month for a continuous year in monthly basis. The monitoring period has included collecting the energy consumption, and reporting on the additional loads, changes of the villas’ operating conditions and climate data to adjust the baseline if required, and then to evaluate the energy performance improvement. For 12 consecutive months starting from Aug. 2014 and ending by July 2015, the total energy savings were 447,628kWh that represent 25.1% of the total energy consumption of the reference year. As shown in Table 2, the annual energy consumption of the adjusted baseline is 1,786,560 kWh, however, after executing the energy savings strategies the annual energy consumption lowered to 1,338,933 kWh for all villas. However, the improvement of energy performance for each villa is not the same. The energy consumption data before the ECMs implementation is totally different between each other. Moreover, each individual villa has a unique improvement of energy performance and different response on the implemented energy strategies. Table 2 shows also the improvement of the energy savings for each villa. The energy savings percentage varies from 15

14.4% to 47.6% depending on the number of energy conservation measures adopted for each villa and their effectiveness against the operating conditions. Another important factor that influences the response of ECMs in each villa is the awareness level. The householders’ buy-in and understanding of the ECMs reflected on the behavior of energy savings strategies acceptance, and accordingly the percentage of savings. The results highlight the energy use index or energy intensity– EUI of each villa before and after the execution of ECMs. EUI is one of the key metrics to benchmark any building against other buildings. It is calculated by dividing the annual energy consumption upon the air conditioned area. The EUI for each villa has been reduced from 471kWh/m²/year to 353kWh/m²/year. Additionally, as illustrated in the same table, each villa has a unique payback period based upon the investment and the archived savings. The payback period of in average is 2.4 years. Individually, it varies from 1.3 years in villa 9 to 4.0 years in Villa 10. However, for villa 7, only 4 months have been monitored since the householder moved on the fifth month and the villa was vacant during the reporting period. On the other hand, as outlined in Figure 9 the energy use savings are the highest in the first quarter compared to subsequent months. The reason is; these first three months falls in summer season in UAE (August, September and October). The energy data baseline is very high in these months. Furthermore, the ECMs were very effective at the first period, thus, the energy savings were the greatest. However, the savings percentage for overall case study was between 20% and 30% except in May and June that was below 20% as shown in Figure 10. Generally in monthly basis, the combination of overall villas’ energy performance improvement is presented in a comparison chart in Figure 11 between the reference year (the adjusted baseline) and the reporting year (monitoring period). It is noticed that the implemented strategies have improved the energy use index in each villa. Furthermore, it has reduced the overall EUI for each villa as presented in Figure 12. However, in order to show the pattern of energy performance for each villa and its reaction against the ECMs, Figures 13.1 to 13.10 present the energy consumption comparison before and after the implementation of ECMs. In the literature, several points should be taken into consideration when executing such energy strategies for housing sector. These considerations could be accounted in general energy savings projects to maintain the results and especially in this study. They are summarized as follows: 1) The home’s occupants should be aware of these new energy conservation measures [3, 45]. This awareness should cover the understanding level of the purpose of these implemented strategies and the main objective of the efficiency approach. 2) In order to sustain the achieved savings, the routine maintenance of energy systems; especially air conditioning units [59], is a key factor to assure the efficient performance continuously of these systems. Previous studies show that more than 50% of the energy use in buildings is used for occupants comfort heating, ventilation and air conditioning 16

(HVAC) [60], thus these results can be use also as benchmarking for housing sector in this climatic zone. 3) Any new additional equipment should be logged. Also, their power should be measured and energy to be calculated in order to adjust the baseline and track the performance. 4) Several operating parameters and factors should be monitored during the measurement and verification period. For instance, the cooling degree days in monthly basis, changes on the occupants’ number and any new refurbishment on the villas, all these factors are essential to identify the achieved energy saving [61]. 5) In case of the power meters are not available, installation of the meters or sub-meters to measure the energy consumption over time is necessary for any energy savings project [62, 63]. Moreover, taking the readings of these meters in regular basis; once monthly at least, is providing a clear confidence regarding the behavior of the executed energy conservation measures. 6

Conclusions

The presented results in this paper show that an improvement of energy performance can be achieved by implementing energy conservation measures in the housing sector in UAE. The discussion outlines that in less than 4 years as a payback period the house could be retrofitted with new energy efficient strategies. These measures are low and medium cost investment that would be affordable for every villa’s owner. However, the poor performance of the building envelope of the existing buildings is one of the challenges that were faced in these selected villas. Thus, it is recommended to mitigate its negative impact on the energy performance by using high reflective materials on the roof, reducing the solar radiation that passes through the windows and decreasing the rate of air exfiltration. On the other hand, the old existing villas need to be upgraded by new technologies especially for the major electricity consumers, such as air conditioning systems and lights. Therefore, controlling these operating systems in order to manage efficiently their status as per the demand is required. This strategy assures optimum energy efficiency without compromising the thermal and visual comfort. Furthermore, the control system is considered as a quick win energy conservation measure and feasible economically. Practically, these ECMs have been monitored for a whole year to track the archived savings. Thus, the energy efficiency for the villas has been improved by 25.1% in average through low and medium cost techniques. This percentage of savings varies from 14.4% to 47.6% of the total electricity according to the individual operating conditions for each villa and the behavior of occupants. The variation of the energy performance improvement percentage for each villa was a result of the difference in the level of understanding and acceptance of the occupants. Therefore, the awareness and education levels are essential part to secure the optimum results. Well-educated occupants shall react and deal positively with the energy efficiency systems that lead increasing the effectiveness of these ECMs. It is worth to mention that the new technologies and high efficient energy system will increase the energy efficiency,

17

however, the positive human’s behavior and awareness level will sustain the energy conservation opportunities benefits. These approaches contribute reducing the generated carbon and GHG emissions and open new perspectives for energy savings strategies to optimize the energy efficiency of the housing sector through these best practices in the houses. Furthermore, they will practically support the sustainable development and improve the energy efficiency for the existing housing sector. Acknowledgements The authors would like to acknowledge the project team of the ECMs execution and the villas’ owners in UAE for providing the data used in this research.

18

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25

Figure 1: Sunrise, sunset, dawn and dusk times in Abu Dhabi [64]

Figure 2: Sun bath diagram of Abu Dhabi (the analysis has been conducted on the 1st of Sept. 2016- today)[64] 26

Figure 3: Architectural details of a sample of the studied villas 27

Figure 4: Energy performance improvement process stages of the villas

Figure 5: Window’s film installation: (a) during the installation, (b) after the installation

Figure 6: The roof materials before and after roof coating measure: (a) before the installation, (b) during the installation, (c) after the installation.

28

Figure 7: The roof surface temperature before and after the roof coating on July 2014 at 11:00am: (a) the roof surface temperature before the installation- 71.4°C, (b) the roof surface temperature after the installation- 47.6°C.

Figure 8: Weather stripping for doors and windows to improve air tightness: (a) during the installation, (b) after the installation

29

80,000

Energy Savings (kWh)

70,000

60,000 50,000 40,000 30,000 20,000 10,000 0

Figure 9: Energy savings per month in (kWh) during the reporting period (Aug.2014 to July 2015) for 10 villas 35%

30%

Energy Savings (%)

25% 20% 15% 10% 5% 0%

Figure 10: Monthly energy savings percentage during the reporting period (Aug.2014 to July 2015) for 10 Villas

30

250,000

Energy Performance Improvement (kWh/year)

Energy Consumption at the reporting period 200,000

Adjusted baseline

150,000

100,000

50,000

-

Figure 11: Energy performance improvements during (Aug.2014 to July.2015) compared to adjusted baseline (Aug.2013 to July.2014) for 10 Villas

31

900

Energy Use Index- EUI kWh/m²/year (After ECMs) Energy Use Index- EUI kWh/m²/year (before ECMs)

Energy Use Index- EUI (kWh/m²/year)

800 700 600

500 400 300 200 100 0 1

2

3

4

5 6 7 Villas' number

8

9

10

Figure 12: The improvement of the Energy Use Index- EUI during (Aug.2014 to July.2015) compared to adjusted baseline (Aug.2013 to July.2014) for 10 Villas

32

Figure 13: Monthly electricity consumption for each villa between the reporting period and reference period. 33

Table 1: Climate Data of Abu Dhabi by RETScreen Climate database. Measured at latitude 24.4ºN, longitude 54.7ºE, elevation 27m above sea level for Heating design temperature 12.9ºC, Cooling design temperature 43.3ºC, and Earth temperature amplitude 21ºC. Daily solar radiation Air temperature Relative humidity horizontal Atmospheric pressure

Heating Cooling Wind speed Earth temperature degree-days degree-days

°C

%

kWh/m²/d

kPa

m/s

°C

°C-d

°C-d

January

18.8

66.0

4.30

100.8

3.5

20.9

0

273

February

20.3

64.2

5.00

100.7

4.0

22.2

0

288

March

22.7

59.7

5.70

100.4

4.2

25.6

0

394

April

26.7

52.4

6.70

100.1

4.0

30.5

0

501

May

31.0

49.0

7.60

99.6

3.9

35.1

0

651

June

33.1

53.1

7.60

99.1

3.9

37.7

0

693

July

34.9

53.5

7.00

98.8

4.0

39.6

0

772

August

35.3

53.3

6.70

99.0

4.0

39.5

0

784

September

32.8

59.0

6.50

99.6

3.7

36.7

0

684

October

29.2

61.3

5.70

100.2

3.4

32.2

0

595

November

24.9

64.0

4.80

100.6

3.2

27.2

0

447

December

20.8

68.4

4.00

100.9

3.3

23.0

0

335

Annual

27.6

58.6

5.97

100.0

3.8

30.9

0

6,417

Month

34

Table 2: The energy performance data before and after the ECMs implementation for each villa Villa's No.

Floors' Area in m²

Energy Use IndexEUI kWh/m²/year (before ECMs)

Annual Energy Consumption of monitoring year (After ECMs)

Energy Use IndexEUI kWh/m²/year (After ECMs)

Annual Energy savings, kWh

Annual Energy savings %

Simple payback period in years (Actual)

Comments

368

Annual Energy Consumption of reference year - Adjusted baseline (before ECMs) 185,798

1

505

97,389

265

88,409

47.60%

2.1

2

368

122,902

334

95,457

259

27,445

22.30%

3.0

The installed ECMs were very effective in this villa. All ECMs installed and their performance matched with the calculations in the reporting period. The installed ECMs were lower than the expected values in this villa. Also, in summer months, it was noticed that the thermostat setpoints were lower than the designed 21⁰C that reduced the effectiveness of the ECMs.

3

368

157,863

429

128,530

349

29,333

18.60%

3.7

4

368

145,285

395

116,495

317

28,790

19.80%

2.5

5

368

143,910

391

103,281

281

40,629

28.20%

2.9

The installed ECMs were lower than the expected values in this villa. Additional loads and appliances have been added to the house that changed the baseline data. New room energy consumption had been calculated to adjust the baseline as a non-routine adjustment. Besides, the A/C system was running at full capacity with a set point of between 18°C and 21°C. This behavior influenced on the related ECMs performance. It is noticed that increasing the awareness level of the occupants will increase the effectiveness of the ECMs. The installed ECMs were effective in this villa. The actual energy savings percentage was equal to the calculated savings theoretically. However, Maintenance issue has been noticed in this villa at the quarter 4. Also, additional load have been noticed and logged in the quarter 2. The installed ECMs performed well in this villa. It is noticed that extra loads were added and then calculated to adjust baseline by 1200kWh/month.

35

6

350

170,780

488

136,404

390

34,376

20.10%

2.6

7

350

53,470

---

43,192

---

10,279

19.20%

---

8

350

221,167

632

152,875

437

68,291

30.90%

1.3

9

516

419,257

813

323,043

626

96,214

22.90%

2.0

10

390

166,129

426

142,268

365

23,861

14.40%

4.0

The installed ECMs were effective in this villa at the first and last quarter. However, in between there was a technical issue in the fresh air handling units and the overall maintenance works. This issue caused to increase the consumption drastically and reduce the savings percentage. The FAHU was in continuous faulty and didn’t deliver the cooling energy required to the thermal zones. Thus, the compressor was working in full capacity. Maintenance work has been conducted in quarter 4 to rectify the problem. Accordingly the savings improved and have appeared in the last quarter of project. This villa has been vacant in the fifth month of monitoring. Thus, the actual payback period wasn’t calculated. The installed ECMs were effective in this villa and better than the expectation. However, in the last quarter the maintenance works were declined by the owner, thus the savings percentages reduced. Also, the roof coating has been disturbed in some areas that reduced its effectiveness. The installed ECMs were effective in this villa and better than the expectation. However, many additional loads and changes have been observed and recorded. The results in this villa were lower than the other villas. Lack of maintenance was noticed that impacted on the overall ECMs energy performance

36