Abstract
JOURNAL OF ASIAN ARCHITECTURE AND BUILDING ENGINEERING 2021, VOL. 20, NO. 1, 61–77 https://doi.org/10.1080/13467581.2020.1781646 BUILDING STRUCTURES AND MATERIALS Thermal performance of insulated concrete block in Sharjah, United Arab Emirates (UAE): continuous monitoring and IR assessment a b Hanan M. Taleb and Khalid AlShuhail a b Faculty of Engineering, British University in Dubai, Dubai, United Arab Emirates; College of Engineering, University of Sharjah, Sharjah, United Arab Emirates ABSTRACT ARTICLE HISTORY Received 31 July 2019 Among the popular construction materials used in the UAE are Insulated Concrete Blocks (ICB). Accepted 29 May 2020 This block is a combination of a unique block design and insulating inserts that enable this block to be highly energy efficient. This paper aims at investigating the thermal performance of KEYWORDS this block during different climatic seasons. An experimental model was constructed in the Insulated Concrete Block; emirate of Sharjah, mainly using this block. Its thermal behaviour was thoroughly studied over performance; building the course of one year by using Continuous Method (CM) and the Infrared Technique (IR) envelope; experimental; UAE method. The main thermal parameters were focused on the Decrement Factor (DF), the Temperature Differences Ratio (TDR) and the Time Lag (Tg). It was found that the ICB does not perform similarly in all seasons, and/or in all orientations. The results show that ICB will perform best in Autumn with an average DF of 0.23, and with an average TDR of 0.56. The biggest value in terms of the Tg is found in Spring with 14.85h. Wind fluctuations can also affect these three parameters. In addition to wind, rain also affects the thermal performance of the ICB. Calibration between the CM and IR methods will be discussed, and detailed analysis will be provided. 1. Introduction developed for exterior wall construction. These materi- Researchers and practitioners have begun to explore als are acceptable as long as they serve the function of the performance of sustainable construction materials exterior walls, including shaping the building, and in the light of depleting resources and environmental exhibiting thermal behaviour, durability and aes- crises. As energy scarcity and global warming are thetics. Consequently, they should be chosen accord- increasingly threatening human sustainability, govern- ing to the climate and affordability (Brock 2015). The ments and organizations must make great efforts to concrete block is popular, and is a precast product that reduce energy consumption and CO emissions. The is used widely in construction. The blocks are formed United Arab Emirates (UAE) is one of the fastest grow- and hardened before they are brought to the construc- ing countries in terms of construction in the world. tion site. In many cases the concrete blocks are either Although the UAE holds considerable energy reserves, solid or have one or more hollow cavities, and their the most important measure in the energy balance of sides may be cast smooth or with a design to fit the the UAE is the total consumption of 110.60 billion kWh desired building design (Allen and Iano 2019). Many of electric energy per year; this is an average of 11,766 researchers have attempted to improve the hollow kWh per capita (World Data 2018). In the UAE, CO concrete blocks because they have recently been in emissions can increase to almost 7.6 million metric great demand. However, the U-value of these hollow tonnes over the next few decades. In fact, the net concrete blocks is still quite high, and does not meet Emirati CO emissions could increase to around the minimum energy requirements for constructing 138.4 million metric tonnes (Radhi 2010). Nowadays, new buildings (Caruana et al. 2017). The idea of due to urbanization and globalization, we are witnes- Insulated Concrete Blocks (ICB) is that they are made sing a rapid development in the construction industry. of concrete mixed with selected aggregate and Thus, it is important to understand how each construc- cement, with the addition of extruded or expanded tion material is performing. Since construction blocks polystyrene – a very well-known insulating material. are bonded together to form the shell of the building This insulating material is specially-designed and and represent a large percentage of the make-up of placed symmetrically while the blocks are being exterior walls, it is important to understand their beha- moulded at the wet concrete stage (Al-Homoud viour in different climatic conditions. There are many 2005). Apart from the insulation aspects, some studies popular construction materials and techniques have stressed the advantage of the concrete blocks’ CONTACT Hanan M. Taleb hanan.taleb@buid.ac.ae Faculty of Engineering, British University in Dubai, Dubai, United Arab Emirates © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group on behalf of the Architectural Institute of Japan, Architectural Institute of Korea and Architectural Society of China. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 62 H. M. TALEB AND K. ALSHUHAIL thermal mass property, in that they have the ability to variability (Méndez Echenagucia et al. 2015). In store heat during the daytime and release it at night. In China, a study analyzed envelope design in terms of a thermal mass wall in a desert climate with high 24-h the energy saving associated with air conditioning ambient temperature and intense sunlight, more heat and the effects of energy saving strategies on the will be stored than can be released outside at night energy consumption of rooms with different orienta- (Zhu et al. 2009). Unfortunately, insulation is not tions in hot summer and cold winter zones. The a priority for architects and developers in the case of results indicated that envelope shading and exterior buildings in the Gulf area where outdoor temperatures wall thermal insulation are the best strategies to in summer can reach 60°C, although it has many eco- decrease AC electric consumption, which achieved nomic and environmental advantages (Al-Jabri et al. a saving of 11.31% and 11.55% respectively (Yu, 2005). Since the building envelope is a crucial part of Yang, and Tian 2008). In the context of the UAE, the building, improving it will lead to a significant a study enhanced the skin performance of hospital increase in energy efficiency (Sadineni, Madala, and buildings by the changing the exterior wall. The ther- Boehm 2011). It is of utmost importance to understand mal properties showed that space conductivity sensi- the thermal behaviour of each construction materials bly changed from −58 to −52 kW. Furthermore, the in harsh weather such as is found in the UAE, in order value of the average external conduction gain to properly exploit them in the construction of build- decreased from 29 to 22 kW (Taleb 2016). ings. Consequently, the aim of this paper is to thor- oughly assess the thermal performance of ICB in a very hot climate. This will be done by adopting the 2.2. Dynamics of thermal mass Continuous Monitoring (CM) and Infrared (IR) techni- In order to comprehend the importance of thermal ques. A model set-up was specifically built in the emi- mass, as well as thermal insulation and their impact rate of Sharjah in the UAE, in order to carry out this on the energy efficiency of a building, it is worth research. Having introduced the rationale, the next understanding some building physics concepts. section will provide a foundation in terms of our According to Concrete Association Australia, concrete knowledge of the topic. is the perfect material to satisfy the requirements for human thermal comfort given that while concrete is a good conductor, it has a high density and a high 2. Literature review volumetric heat capacity. This gives concrete a very 2.1. The importance of exterior walls with regard high thermal mass (the capacity to store energy) to achieving energy efficiency (National Concrete Australia 2019). Figure 1 explains the daily temperature profile at points through The building envelope acts as a physical separator a concrete wall. between the inside and the outside. According to the International Code Council (ICC) (2018) the exter- 2.2.1. Decrement factor (DF) ior walls are very important in any building envelope, The term ‘decrement factor’ is the amount by which and are there to provide a building with good conditions are moderated by an element of a building. weather-resistant material (International Code It is also expressed as the ratio between the internal Council 2018). Many researchers have attempted to surface cyclic temperature variation compared to the improve energy efficiency through the design of the external surface. It also means that it is the amount by building envelope. For example, a study in Turkey which the peak is reduced by the time it reaches the managed to reduce 40.1% of the energy consumption inner surface if the outer surface experiences of the baseline (Sozer 2010). Another interesting a temperature peak in the summer (Asan 2006). study used a simulation–optimization tool coupled � � � � � � with a generic algorithm by selecting optimal values DF ¼ T T = T x¼LðmaxÞ x¼LðminÞ x¼0ðmaxÞ � � from a comprehensive list of parameters associated T (1) x¼0 ðminÞ with the envelope in order to minimize energy use for residential buildings, including exterior walls con- where: - struction (Tuhus-Dubrow and Krarti 2010). In order DF = Decrement factor to achieve high performance buildings, it is vital to (T ) = maximum temperatures on the indoor x=L(max) decide on the right construction materials in the early surfaces of the wall. design stage. The orientation is important as one of (T ) = minimum temperatures on the indoor x=L(min) the studies highlighted the importance of a small surfaces of the wall. overall Window-to-Wall Ratio of buildings in (T ) = maximum temperatures on the outdoor x=0(max) Palermo, Torino, Frankfurt and Oslo. The area of the surfaces of the wall. south-facing windows was high compared to the (T ) = minimum temperatures on the outdoor x=0 (min) other orientations and characterized by a higher surfaces of the wall, respectively. JOURNAL OF ASIAN ARCHITECTURE AND BUILDING ENGINEERING 63 Figure 1. Daily temperature profile at points through a concrete wall (cibsejournal 2019). 2.2.2. Temperature difference ratio (TDR) 2.3. Previous studies on DF, TDR and Tg The temperature difference ratio is used to measure Back in 1999, a study concluded that thermophysical the thermal performance of a building envelope. To properties have a profound effect on the time lag and calculate it, it requires temperature differences the decrement factor, even when the computations between indoor and outdoor environments and wall were repeated for different building materials (Asan surface temperatures (Knaack and Koenders 2018). and Sancaktar 1999). Later, the authors investigated TDR ¼ ½ T T � = ½T T � (2) a wall’s optimum insulation position from maxout maxin maxout minout a maximum time lag and minimum decrement factor where: point of view. It was concluded that placing half of the TDR = Temperature Difference Ratio. insulation on the inner surface, and the other half on T = Maximum temperature outside. maxout the outer surface of the wall gives a minimum decre- T = Maximum temperature inside. maxin ment factor. On the other hand, a maximum time lag T = Minimum temperature inside. minout was obtained in the case of placing two slices of insu- lation at a certain distance apart inside the wall. 2.2.3. Time lag Placing half of the insulation on the mid-centre plane The time lag, measured in hours, is the time needed for of the wall and half of it on the outer surface of the wall heat to pass through a material. A construction with gives very high time lags and low decrement factors high thermal mass (high heat capacity and low con- (close to optimum values) (Asan 2000). A recent study ductivity) will have a large thermal lag. The time lag in 2017, indicated that the employment of phase can be calculated using the following formula: change materials in walls of a building has a pronounced effect on the time lag and the decre- T ¼ t t (3) g Tz¼LðmaxÞ T¼ Z¼ 0 ðmaxÞ ment factor. It is concluded that a significant amount of heating energy can be saved, and thermal comfort where: - can be considerably enhanced, by incorporating phase T = represents the time lag. change materials into external walls (Bilgin and Arici t = represents the time that the indoor Tz=L (max) 2017). surface temperatures are at a maximum. t ) = represents the time that the outdoor T=Z=0(max surface temperatures are at a maximum. 2.4. State of the art The concept sometimes referred to as “thermal lag” describes a body’s temperature with respect to time as In this section, we detail the literature that was a result of its thermal mass. A body with high thermal consulted to determine the current status of mass (high heat capacity and low conductivity) will research into concrete block performance. Apart have a large thermal lag (Revolvy 2019). from theoretical studies, no detailed experimental The term in this case can be calculated as: studies have been performed in the UAE on the pffiffi thermal performance of concrete blocks (See Table 2 � α � Ω 1). This paper provides a novel view on the most Thermal lagðsÞ ¼ (4) significant contributors to the thermal behaviour of where:- building envelopes that are constructed by using α = Thermal diffusivity (m /s) ICB in an extremely hot climate. This paper contri- −1 Ω = External angular frequency (s ) butes to the existing literature by comprehensively L = thickness (m) reviewing the concepts in a hot climate situation in 64 H. M. TALEB AND K. ALSHUHAIL Table 1. Summary of key research on concrete blocks. No. Authors Year Title of the study Aim Findings Citation Halwatura 1 Udawattha, 2018 Thermal performance and structural To and cooling analysis of bricks, cement blocks, and mud concrete blocks investigate thermal analysis and Brick walling materials have better (Udawattha and Halwatura 2018) structural cooling of brick, time lag and decrement factor at cement block and mud concrete a thickness of 225 mm. block walling materials to compare the thermal comfort of different walling materials. 2 Shaik et al. 2016 Optimizing the position of To optimize the position of The composite roof with expanded (Shaik and insulating materials in flat roofs insulating materials in flat roofs, polystyrene insulation located at Talanki exposed to sunshine to gain materials included polystyrene, the outer side and at the centre 2016) minimum heat into buildings foam glass, rock wool, rice husk, plane of the roof is found to be under periodic heat transfer resin-bonded mineral wool, and the best roof from the lowest conditions cement plaster decrement factor (0.130) point of view 3 Roberz et al. 2017 Ultra-lightweight concrete: energy To investigate the potential of Ultra-lightweight concrete can (Roberz and comfort performance ULWC building envelopes in therefore be a suitable et al. evaluation in relation to terms of energy efficiency and construction material in 2017) buildings with low and high thermal comfort. buildings with intermittent thermal mass operation, but in other cases it can be outperformed by conventional construction materials with low or high thermal mass. 4 Xuan et al. 2016 Development of a new generation assessed the potential of adopting The experimental results showed (Xuan, of eco-friendly concrete blocks an accelerated mineral that incorporating the Zhan, by accelerated mineral carbonation process to produce carbonated RCA in concrete and Poon carbonation a new generation of concrete blocks led to an increase in 2016) blocks with recycled concrete strength by 2%–18% aggregates (RCA) 5 Hasan et al. 2016 Effect of phase change materials Phase change material (PCM) A temperature drop of 8.5% and (Hasan et al. (PCMs) integrated into contained in an insulated a time lag of 2.6 h are achieved in 2016) a concrete block on heat gain concrete block is tested in peak indoor temperature, prevention in a hot climate. extremely hot weather in the rendering a reduction of 44% in United Arab Emirates (UAE) to heat gain. evaluate its cooling performance. An insulated chamber is constructed behind the block containing PCM to mimic a scaled-down indoor space 6 Xing et al. 2018 a new energy-efficient building The purpose of this research is to Heat transfer coefficient of wall (Xing et al. system based on insulated put forward a new energy- could be reduce by up to 45%. 2018) concrete perforated brick with efficient building system that can When thickness of insulating a sandwich meet the energy saving layer was 65 mm, the heat requirement of 65% for public transfer coefficient of a wall buildings in cold areas based on made by modified bricks could modified insulated concrete reach a minimum limit 0.45 and perforated brick with a sandwich. could meet energy saving requirement of 65% for buildings in cold area 7 Cianfrini 2017 Dynamic thermal features of To numerically study the heat The time lag and decrement factor (Cianfrini, et al. insulated blocks: actual transfer in blocks with different were all studied in terms of de Lieto behavior and myths infill insulating materials dynamic thermal insulation. Vollaro, A lower front mass leads to and a higher time lag. Once the Habib equivalent thermal diffusivity of 2017) blocks is defined, there is a strong correlation between time lag and the reciprocal of equivalent thermal emissivity. light of the shortage of relevant studies. It will allow which the project/material is having, or has had, us to draw future recommendations with regard to the desired impact. Continuous monitoring and the actual performance of ICB, and when or where real experimentation can be compared with simula- we ought to use them in terms of building orienta- tions which might have errors and suffer from a lack tion. The strength of this research lies in continuous of accuracy. Although this study uses Sharjah as the monitoring and real experimentation which offers location for the case study, it could be argued that many benefits including tracking performance in most of the findings are applicable to similar cli- real life, making immediate accurate decisions, matic and environmental conditions. The next sec- ensuring the most effective and efficient use of tion will highlight the methodology adopted for this resources, and finally evaluating the extent to research. JOURNAL OF ASIAN ARCHITECTURE AND BUILDING ENGINEERING 65 and Harte 2017a). IR also works very well outdoors, as 3. Methodology one study used it to quantify the heat losses through 3.1. CM and IR methods thermal bridges influenced by wind velocity (O’Grady, Lechowska, and Harte 2017b). In short, CM and IR seem Experimental research is considered as one of the very effective tools if they are used correctly and founding quantitative research methods. In this field, efficiently. a set of variables will be kept constant while the other set of variables are being measured as the subject of the experiment (Groat and Wang 2013). Many building 3.2. Research design researchers adopt the CM approach to optimise build- ing performance. In Italy, CM was used to test the For the sake of this research an experimental model thermal effect of an innovative cool roof on residential (zone) was built in real in Sharjah, UAE on the back buildings (Pisello and Cotana 2014). Another interest- yard of the National Laboratory Lab owned by ing study used the CM of occupant behaviour inte- the second author of this research (See Figure 2). grated long-term to a prediction models in order to The external dimensions of the model are 4.05 m assess the impact of office energy consumption (Piselli in length X 2.40 m in width X 3.46 m in height, with and Pisello 2019). The CM approach is also used to internal dimensions of 3.59 × 1.96 x2.72 m. The main assess construction materials and their thermal perfor- construction is ICB blocks with minimum use of plas- mance. A study analysed the long- and short-term ter and wood beams for celling support. That means effects of temperature and humidity on the structural all the walls and ceiling and even the floor is made properties of adobe buildings using CM (Zonno et al. of ICB (See Table 2). Inside this zone there is 2019). In addition, CM was adopted by a study aimed a covered opening of 0.60 m X 0.60 m on the celling, at determining the setting and hardening of mortar for the air to escape. This zone has a door 0.80 m and concrete (Reinhardt and Grosse 2004). X 1.20 m with two windows 0.30 m X 0.60 m on the Nonetheless, the IR method is also a very effective South elevation. Two Extech RH520A humidity and tool to monitor and assess thermal conditions by col- temperature chart recorders with a detachable probe lecting data. According to Balaras and Argiriou, this were used, one inside the model (hung from the method involves the detection of IR electromagnetic ceiling to ensure accurate measurements) and one radiation emitted by the inspected object or building instrument located outside on the roof (See Figure 2 component in the field of architectural research. The for the exact locations of these instruments). The collected information can be used as part of other continuous monitoring took place from investigative procedures to identify potential pro- August 2018 through to August 2019. The first two blems, quantify potential energy savings, schedule main climatic factors that were taken included the interventions, and set priorities (Balaras and Argiriou temperature and relative humidity for the model. 2002). A study used the IR method to test the thermal Secondly, the three mass parameters were calculated bridge heat flow rate in buildings (O’Grady, Lechowska, based on temperature measurement for the year in Figure 2. The experimental case study and research instruments with their locations. 66 H. M. TALEB AND K. ALSHUHAIL Table 2. ICB specifications. Parameter Value Image Dimensions 400 mm x 200 mm x 200 mm Insert Thickness 60 mm 2 2 Compressive Strength 7.5 N/mm & LB: 12.5 N/mm Thermal Transmittance 0.48 W/m /K Chloride content 0.05% Sulphate content 0.5% Blocks per m 12.5 Polystyrene Insert Density 25 kg/m (min) Polystyrene Thermal 0.111 W/m/K Conductivity Polystyrene Thermal 0.5 W/m /K Transmittance More specifications high load bearing, fire resistant, excellent sound insulation and high thermal efficiency. the form of DF, TDR and Tg in order to fully under- when the country is exposed to the greatest amount stand the thermal performance of the ICB (see Table of solar radiation. As shown, the highest discrepancy 1) in terms of its specifications. The next step was appeared in the month of August in terms of tem- the use of the IR technique involving an FLIR E6 with perature between inside and outside. The RH has MSX Enhancement Display 3” colour LCD (7.62 mm), minimal differences between inside and outside On-board 640 × 480 Digital Camera. Its weighs only throughout almost all the three months of summer, 1.2lbs and offers 2% accuracy. This provided simulta- which means that the RH was stable. Obviously, neous storage of IR/Visual/MSX images FLIR E6 hav- there is an inverse relationship between the RH and ing 19,200 pixels (160 x 120). For the average daily temperature. For example, whereas the highest tem- representation of the temperature, this was mea- perature in July was at midday, the RH on the other sured every three hours from 6 am (before sunrise) hand was low. The RH is relatively high at night until the next day at 6 am. The average monthly when the temperature is, simply, was low, can hold representation of the temperature was measured at more water vapor than cool air, relative humidity the beginning of each week of the same month, and falls when the temperature rises if no moisture is then the monthly average is calculated based on added to the air. From 12:44 am till 6:44 am in all four days or five according to the number of days three months the temperature inside and outside is of weeks in the month. The IR readings were taken close. From 6:44 am till 5:44 pm the differences are every Saturday of each month (4 − 5 days per noticeable. This is due to the solar radiation that month) at every 3 hour per day, starting at 6.0 AM create a difference between inside and outside. The and running through to 6.0AM on the following day. RH on the inside in most cases is higher than out- Readings were taken both inside and outside the side, simply because the outside is subjected to the zone for the different months (September to prevailing wind. August). The three main mass parameters were cal- culated accordingly – the DF, TDR and Tg. An 4.1.2. DF, TDR and Tg for one year attempt was made to calibrate the readings of CM The DF, TDR and Tg were calculated based on the and IR readings. Both methods were used to assess CM for the whole year. Figure 4 illustrates the aver- all the orientations, inside and outside, and in differ - age of these parameters. Interestingly, the month of ent seasons. February shows the least values. By checking the weather again, the month of February in 2019, wit- nessed unusual heavy rain which minimised the 4. Results and findings differences between inside and outside. Thus, these three parameters were kept low. The DF 4.1. CM method value was at a maximum in the months of April, 4.1.1. Temperature and RH readings for 24 hours May and June, and lower in the other months. This during the summer season can be explained by going to Equation 1. If the DF The temperature was recorded for 24 hours through- is high it means that the Tx = 0(max) – Tx = 0 (min) out one whole year, both inside and outside the ICB is low. The benefits of decrement delay are only model. However, due the space limitations of this realised when the outside temperature fluctuates paper, it is difficult to present the total period of significantly higher or lower than the inside tem- time. Instead, Figure 3 summarises the hottest perature. TDR were maximum in the months of months in UAE which are June, July and August, September and March. The higher the value of the JOURNAL OF ASIAN ARCHITECTURE AND BUILDING ENGINEERING 67 Figure 3. Temperature and RH readings for 24 hours for summer season by CM. TDR, the better the performance of the test model. model in terms of DF, TDR and Tg per day. The values It is agreed that the thicker and more resistant the were calculated during 30 days per month of August, material, the longer it will take for heat waves to September, October, and November 2018. Figure 5 th pass through, which also means the longer hours of illustrates the detailed results. The DF on 25 time lag indicates a better performance on the part October shows a very high jump of 0.32. This scenario th of the material. The time lag was at a maximum in was repeated on 8 November reaching also 0.32. As the months of April and May. previously mentioned, if the DF is high it means that the Tx = 0(max) – Tx = 0 (min) is low. High readings on certain days could be explained by the wind readings. 4.1.3. Detailed DF and TDR per day th 25 October and 8 November 2018 experienced a hot In order to understand the DF, TDR and Tg, it might wind came from the North West, whereas other days worth observing the detailed performance of the ICB 68 H. M. TALEB AND K. ALSHUHAIL Figure 4. DF, TDR and Tg values for one year by CM. during these months had less external wind effect. The the low heat retention during Autumn. The worst season higher these two days in DF, the lower the TDR read- was the summer with a DF of 0.39. This is probably due to th ings. The highest TDR readings were on 9 September the high heat retention during the summer, since the and 2 November 2018. blocks cannot breathe, causing high DF and low TDR. The TDR is better also in Autumn with an average of 0.56. Again, the summer performed least well with an 4.1.4. DF, TDR and Tg per season average of 0.40. In terms of Tg, Spring performed very In order to understand the three parameters in relation to well, reaching an average of 14.85 h and the lowest is the season, the average of each 3 months was calculated. Autumn with an average of 6.92 h. It is agreed that the Figure 6 illustrates the results. DF performed very well in careful selection of materials can ensure that high solar Autumn with an average of 0.23. This is probably due to JOURNAL OF ASIAN ARCHITECTURE AND BUILDING ENGINEERING 69 Figure 5. Detailed DF and TDR per day for three months by CM. irradiance striking the outside of a wall is not felt inside resolution in order to obtain a holistic and overall the space until after the building’s use has ended for assessment through multivariate data. A closer look the day. at the DF to find where the values are less in terms of orientaiton, finds that it is the West wall (blue line) and the South wall (green line). The North wall has a high DF because it is simply not exposed to direct radiation. 4.2. IR Method The graph could be helpful if the months are divided 4.2.1. Average temperature readings for five into sesaons. For example, in the spring seasons – outside surfaces over five months March, April and May – the North has high readings, The temperature was recorded for 24 hours for the and the best orientation for the DF will be West. TDR is whole year. Table 3 illustrates the average tempera- low in an East direction (Yellow line) and has a high ture per hour inside and outside the ICB model for range in other orientaitons. The Tg is high and works five outside surfaces, North, South, East, West and the best in terms of the top (Red line) orientation. the top (roof). 4.2.2. DF, TDR and Tg per year 4.3. CM and IR calibration Following the temperature average calculations with The temperature was taken by CM and IR for the regard to IR, the DF, TDR and Tg were calculated for month of September to allow for calibration. This one year. Figure 7 summarises the readings. Figure 6 is mathematical comparison will ultimately ensure a radar chart of the DF, TDR and Tg for one year for all the accuracy of both techniques. To calibrate and orientations. The advantages of using this kind of chart evaluate the two-measurement methodology, the is the fact that many variables can be represented next measurements for September were calibrated as to each other, while still giving each variable the same 70 H. M. TALEB AND K. ALSHUHAIL Figure 6. Average DF, TDR and Tg per season for three months by CM. an example of both measurement methods. The the east wall, the west wall, and the roof. Same thermal imaging-IR of the different wall’s orienta- Figure 8, represents the internal and external tem- tions in the model, as well as the continuous peratures using both measurement methods, measurement of CM of a point in the middle of where compatibility is also shown. Apart from the inner perimeter, and a point in the outer that, and as is obvious, having this intersection perimeter of the model was done. Figure 8 sum- proves that both methods are valid and accurate. marizes the calibration of the CM and IR average temperature readings of the 5 walls inside and outside in September. In the same figure of the 5. Discussion comparison of the external temperature -OUT of 5.1. Effect percentages of DF, TDR and Tg on the both methods, it is observed that the average five outside surfaces per season temperature in the continuous measurement method is compatible with the total measurement For early stage design considerations directed at of the IR temperature. The temperature in the energy efficiency, the orientation of a house is the directions is both the north wall, the south wall, first decision architects make in the design process. JOURNAL OF ASIAN ARCHITECTURE AND BUILDING ENGINEERING 71 Table 3. IR readings of average temperature per hours of ICB model: North, South, East, West and the top, inside and outside. Time and Wall Time Time Time Top Top-Inside Mar. Top-Outside Mar. Top Top-Inside Jun. Top-Outside Jun. Top Top-Inside Jul. Top-Outside Jul. Top Top-Inside Aug. Top-Outside Aug. 06:00 AM 31.6 30.3 06:00 AM 34.3 33.1 06:00 AM 36.6 35.5 06:00 AM 36.5 34.2 09:00 AM 33.3 50.2 09:00 AM 34.8 52.2 09:00 AM 37.8 52.4 09:00 AM 37.1 52.7 12:00 PM 35.0 58.1 12:00 PM 36.2 59.8 12:00 PM 40.0 61.6 12:00 PM 39.2 59.8 03:00 PM 35.5 54.7 03:00 PM 36.6 55.0 03:00 PM 40.1 59.8 03:00 PM 38.5 56.3 06:00 PM 34.0 41.4 06:00 PM 36.5 41.2 06:00 PM 39.3 44.6 06:00 PM 38.1 42.3 09:00 PM 34.2 33.9 09:00 PM 36.1 36.6 09:00 PM 39.0 39.5 09:00 PM 38.1 37.9 12:00 AM 33.7 31.8 12:00 AM 35.5 34.2 12:00 AM 38.5 37.1 12:00 AM 37.4 35.6 06:00 AM 32.0 30.1 06:00 AM 33.9 33.6 06:00 AM 37.0 35.2 06:00 AM 35.9 34.0 North North-Inside Mar. North-Outside Mar. North North-Inside Jun. North-Outside Jun. North North-Inside Jul. North-Outside Jul. North North-Inside Aug. North-Outside Aug. 06:00 AM 32.4 28.7 06:00 AM 35.6 31.2 06:00AM 37.7 33.6 06:00 AM 37.4 33.0 09:00 AM 32.9 33.1 09:00 AM 35.3 35.4 09:00 AM 38.1 37.9 09:00 AM 37.1 36.4 12:00 PM 34.2 37.3 12:00 PM 36.4 39.4 12:00 PM 38.9 42.0 12:00 PM 37.1 40.7 03:00 PM 34.7 39.2 03:00 PM 36.9 40.4 03:00 PM 40.0 43.4 03:00 PM 38.7 41.3 06:00 PM 35.1 35.3 06:00 PM 37.4 37.7 06:00 PM 40.0 40.2 06:00 PM 38.9 38.2 09:00 PM 34.8 32.8 09:00 PM 36.9 34.9 09:00 PM 39.7 37.4 09:00 PM 38.8 35.8 12:00 AM 34.4 31.4 12:00 AM 36.8 33.3 12:00 AM 39.4 36.0 12:00 AM 38.4 34.3 06:00 AM 32.9 28.7 06:00 AM 35.1 31.1 06:00 AM 38.0 33.5 06:00 AM 37.1 32.2 East East-Inside Mar. East-Outside Mar. East East-Inside Jun. East-Outside Jun. East East-Inside Jul. East-Outside Jul. East East-Inside Aug. East-Outside Aug. 06:00 AM 32.4 28.7 06:00 AM 35.7 31.1 06:00 AM 37.6 33.9 06:00 AM 37.4 32.9 09:00 AM 32.8 40.1 09:00 AM 35.3 41.9 09:00 AM 37.8 43.6 09:00 AM 37.1 43.2 12:00 PM 34.1 39.9 12:00 PM 36.4 42.4 12:00 PM 38.8 45.0 12:00 PM 37.8 44.2 03:00 PM 34.6 39.6 03:00 PM 37.1 41.4 03:00 PM 39.9 44.6 03:00 PM 38.7 42.8 06:00 PM 35.2 35.7 06:00 PM 37.5 38.3 06:00 PM 40.1 41.0 06:00 PM 39.0 39.0 09:00 PM 34.9 33.2 09:00 PM 37.1 35.3 09:00 PM 39.8 37.9 09:00 PM 38.9 36.5 12:00 AM 34.5 31.3 12:00 AM 36.7 33.6 12:00 AM 39.4 36.1 12:00 AM 38.3 34.7 06:00 AM 32.8 28.5 06:00 AM 35.2 31.6 06:00 AM 37.8 33.6 06:00 AM 37.1 32.4 West West-Inside Mar. West-Outside Mar. West West-Inside Jun. West-Outside Jun. West West-Inside Jul. West-Outside Jul. West West-Inside Aug. West-Outside Aug. 06:00 AM 32.4 28.8 06:00 AM 35.3 31.6 06:00 AM 37.3 34.1 06:00 AM 37.0 33.4 09:00 AM 32.7 36.8 09:00 AM 35.0 39.2 09:00 AM 37.5 42.2 09:00 AM 36.8 41.2 12:00 PM 33.6 41.9 12:00 PM 35.8 44.6 12:00 PM 38.5 47.2 12:00 PM 37.5 46.0 03:00 PM 34.0 55.7 03:00 PM 36.4 56.4 03:00 PM 39.3 59.5 03:00 PM 38.0 56.7 06:00 PM 34.5 37.7 06:00 PM 37.5 40.3 06:00 PM 40.0 43.1 06:00 PM 38.5 41.2 09:00 PM 34.9 34.1 09:00 PM 37.3 36.4 09:00 PM 39.8 39.3 09:00 PM 38.9 37.9 12:00 AM 34.4 32.0 12:00 AM 36.7 34.2 12:00 AM 39.3 37.0 12:00 AM 38.0 35.8 06:00 AM 32.6 28.9 06:00 AM 34.9 31.8 06:00 AM 37.6 34.1 06:00 AM 36.5 32.9 South South-Inside-Mar. South-Outside Mar. South South-Inside-Jul. South-Outside Jul. South South-Inside-Jul. South-Outside Jul. South South-Inside-Aug. South-Outside Aug. 06:00 AM 31.8 29.9 06:00 AM 34.8 32.9 06:00 AM 37.0 34.9 06:00 AM 36.9 34.6 09:00 AM 32.2 37.9 09:00 AM 34.6 40.5 09:00 AM 37.4 42.9 09:00 AM 36.7 43.3 12:00 PM 33.1 43.5 12:00 PM 35.3 45.5 12:00 PM 38.0 48.9 12:00 PM 37.4 49.2 03:00 PM 33.8 42.4 03:00 PM 36.2 43.4 03:00 PM 39.1 47.9 03:00 PM 37.8 47.1 06:00 PM 33.9 35.4 06:00 PM 36.9 37.9 06:00 PM 39.4 41.2 06:00 PM 38.3 39.2 09:00 PM 34.3 32.6 09:00 PM 36.7 34.8 09:00 PM 39.2 37.5 09:00 PM 38.5 36.6 12:00 AM 33.7 31.8 12:00 AM 36.1 34.2 12:00 AM 38.7 37.3 12:00 AM 37.7 35.3 06:00 AM 32.3 30.1 06:00 AM 34.5 32.5 06:00 AM 37.4 35.1 06:00 AM 36.3 33.8 72 H. M. TALEB AND K. ALSHUHAIL parameter for the model’s total thermal parameters with different climatic separation, as well as the direction of the wall. This is used to determine the percentage of the largest participation in thermal dealings based on the direction of the wall, or according to the climatic season, and will be fol- lowed from the analysis of the results as shown below. For the deeper analysis of the three thermal parameters, DF, TDR and Tg, on the proportions of the participation of each wall’s orientation by direc- tion, or in terms of each climatic season, there are two directions as the horizontal axis of the four climatic seasons or the five wall orientation as for the vertical axis, representing the %DF, %TDR and %Tg, as shown in Figure 9, which illustrates the six relationships. For the first thermal parameter DF, during the four season climates of autumn, winter, spring and summer, despite the thermal character- istics, the Northern wall and the Eastern wall are the most significant, with the least influenced being the Western and the Southern walls. In terms of the second parameter, TDR, during the four climatic seasons, the Southern wall, the Western wall and the roof are the most affected, while the Eastern and Northern walls are the least affected. The third factor studied, Tg, is the effect of the roof, the Western wall and the Northern wall, and the lower effect of the Eastern and Southern walls. Generally, the effect of the orientation of each wall in a house on the energy thermal parameter requirements for thermal comfort, especially in a naturally-ventilated house in a hot climate, needs to be considered. In addition, the wall orientation percentage given above in this study will be also helpful when it comes to the interior unit capacity selection of the cooling system. 5.2. Summarised thermal performance of 5 orientations of the ICB model The significance of the orientation of the overall build- Figure 7. Radar chart of average DF, TDR and Tg for one year. ing wall in terms of thermal performance has an impact on the building’s overall thermal performance and on the design cooling needed to obtain thermal Consequently, it is necessary to obtain a clearer comfort for the occupants. Figure 10 summarises the picture of how the various walls of a building envel- whole study in terms of the thermal performance of 5 ope affect the building energy thermal parameters. orientations throughout the year. In conclusion, to This can be used as a tool to save energy for the reduce summer overheating, a low decrement factor building. It is necessary to display the relative pro- (DF) is required, a high total difference temperature portions of each wall orientation and climatic sea- ratio (TDR), and a decrement delay of 6 to 12 hours. son on the thermal parameters by using a statistical This study of the ICB model can be summarised in graphic pie chart. As shown in Table 4, the 12-pie three points: charts show the three thermal parameters sharing DF, TD and Tg through the four climatic seasons. DFðICBÞ ¼ 0:17� DF þ 0:29 � DF Top Roof North wall model The study of these forms in general indicates that þ 0:15� DF South Wall there is a clear variation in the proportion of the þ 0:27� DF þ 0:12� DF East Wall West Wall participation of each wall with regard to each JOURNAL OF ASIAN ARCHITECTURE AND BUILDING ENGINEERING 73 Figure 8. Calibration of CM and IR average temperature readings of 5 walls inside and outside in September. TDRðICBÞ ¼ 0:25� TDR 6. Conclusion Top Roof model þ 0:13� TDR North wall This paper investigated the different measurements of þ 0:25� TDR South Wall internal and external temperature and relative humidity, þ 0:14� TDR þ 0:24� TDR over hour, day and month of the model. The empirical East Wall West Wall findings can be summarized as follows: (1) despite the characteristic thermal properties of the ICB in terms of 1:3 Tg ðICBÞ ¼ 0:17� Tg reducing the maximum temperature values throughout Top Roof model the day, the internal temperature is not constant þ 0:29� Tg North wall throughout the day. (2) the internal temperature rises at þ 0:15� Tg South Wall night despite falling outside. (3) relative humidity and þ 0:27� Tg East Wall temperature are inversely proportional, although the þ 0:12� Tg West Wall internal humidity increases during the day despite falling 74 H. M. TALEB AND K. ALSHUHAIL Table 4. Effect percentages of DF, TDR and Tg on the outside surfaces per season. DF TDR Tg (H) Autumn Winter Spring Summer outside (4) the thermal parameters DF, TDR and Tg are orientation (north-south-east-west) (8) the roof is different, and their values are variable over the order of a fundamental factor with regard to TDR and Tg, days and months. Over the months, the values of DF, TDR as the northern wall is on DF parameters in terms of and Tg vary with regard to the summer months and with their great effect and contribution (9) the study high temperature values (5) for the thermal parameters proved that the thermal IR methodology is practical DF, TDR and Tg of the ICB Model in the four climatic and quick when it comes to assigning the para- seasons, the DF is in the range 0.23–0.26-0.38–0.39 during meters to the whole model (10) from the study the summer season, the TDR is in the range 0.56–0.54- and analysis of the IR measurements and DF, TDR 0.44–0.40 during the summer season, and Tg is in the and Tg throughout the four climatic seasons, it is range 6.92–9.29-14.85–8.75 h during the summer Season noted that: the DF of the model share the different (6) in the study of the internal and external measure- directions of the north walls as well as the more ments of the thermal imaging of the model, including eastern wall orientations of the remaining walls. In the different outside surfaces – Top (roof) – North – terms of the TDR, the most influential TDR is in South – East – West, there is a clear pattern of values terms of the southern direction, the western direc- with the 12 month period and the four climatic seasons tion and the roof. Aimed at the Tg of the most (7) the ratio of the orientation of the different walls to the influential model the ceiling and the northern direc- values of the block model in terms of thermal parameters, tion and the most influential western direction than depends on the climatic season (autumn-spring- the other orientation. In addition, based on the season, summer-winter) and the direction of the wall as well as the wall orientation, the percentages revealed JOURNAL OF ASIAN ARCHITECTURE AND BUILDING ENGINEERING 75 Figure 9. Percentage contributions of DF, TDR and Tg of five wall orientations by season. in this study give a clear picture of how various walls of the unit capacity of the interior cooling system. The the building envelope affect the building’s energy con- authors recommends the following as future areas of sumption. This will also be helpful for the selection of research: (1) to carry out similar research in temperate 76 H. M. TALEB AND K. ALSHUHAIL Figure 10. DF, TDR and Tg of five wall orientations throughout the year. and cold climates (2) to study sustainable blocks other Decrement Factor Point of View.” Energy and Buildings 32 (2): 197–203. doi:10.1016/S0378-7788(00)00044-X. than ICB (3) to study the ICB in real constructed build- Asan, H. 2006. “Numerical Computation of Time Lags and ings involving different construction materials. Decrement Factors for Different Building Materials.” Building and Environment 41 (5): 615–620. doi:10.1016/j. buildenv.2005.02.020. 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Journal
Journal of Asian Architecture and Building Engineering
– Taylor & Francis
Published: Jan 2, 2021
Keywords: Insulated Concrete Block; performance; building envelope; experimental; UAE
