An energy model of an educational building located at the German Jordanian University in Jordan was constructed utilizing DesignBuilder computer software using real data recorded on the site.
2.1. Location and the Building Characteristics
The university building is located in Madaba province, which is around 35 km to the southwest of Amman, the capital city of the Hashemite Kingdom of Jordan, and is about 30 km to the northwest of Queen Alia International Airport. Madaba is situated in central Jordan and has a population of nearly 90,000 people.
A hot and dry climate is characteristic of Jordan. In fact, summers are long, hot, and dry, whereas winters are short and cool. Jordan’s location plays a part in this pattern of weather, as it is situated between the Arabian Desert and the eastern Mediterranean. The former is characterized by subtropical aridity, while the latter is characterized by subtropical humidity. January is the coldest month, with temperatures varying from 5 °C to 10 °C. In contrast, August is the hottest month, with temperatures varying from 20 °C to 35 °C. The majority of days are sunny throughout the year in Jordan with an estimate of more than 300 days of sunshine. This is equivalent to a sunshine duration of about 3125 h/year [
33]. In this analysis, we did not have hourly recorded weather data on the site for this specific period, so we used the hourly weather data built in the software’s location library. The hourly weather data were utilized for carrying out the annual simulation.
The maximum temperatures were recorded in July and August, respectively. On the other hand, the minimum temperature was recorded in January. The highest velocity of wind was logged in February and March, whereas the lowest velocity of wind was logged in October. The university under discussion is a 5-story building occupying an area of 13,000 m
2. The area of each floor is illustrated in
Table 1. It is mainly comprised of classrooms, applied engineering science laboratories, and offices for faculty members and management workers, and their numbers on each floor are shown in
Table 1. Moreover, there is an auditorium and a cafeteria, which are located on the first floor.
The building in question was modeled in 5 blocks. Each block resembles 1 story of the real building, as illustrated by
Figure 1. The third and fourth floors have the same architectural design as the second floor.
In general, the building is operated 5 days a week (from Sunday to Thursday). However, it might be operated on Saturdays. Regarding the working hours, the building is operative 8 h per day (from 8 a.m. to 4 p.m.) for regular academic semesters (from October to July) and for 7 h for the summer semester (from July to September).
The materials used in each component of the building envelope and their corresponding thicknesses were acquired from the building’s architectural design schematics (see
Table 2).
However, their corresponding thermal conductivity values were obtained from the literature/university laboratories and American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) standard as follows [
34]:
The lighting in the building was designed as stated by ASHRAE 90.1 standard.
The building can be divided into 4 thermal zones, which are classrooms, laboratories, offices, and corridors, since the aforesaid utilities are the only thermally conditioned areas of the building. Besides, they almost account for the heaviest energy consumption of the building by themselves.
The building is supplied with 2 compression chillers with a cooling capacity of 710 kW. One of the chillers also functions as a heat pump. This heat pump is aided by two 200 kW gas boilers that are installed for heating purposes. Moreover, the building is fitted with 3 air handling units to cover its ventilation load.
The building ventilation load was calculated according to ASHRAE 62.1 standard.
The readings were obtained for monthly energy consumption from the Building Management System (BMS) for each month of 2019. Moreover, those readings were recorded by the BMS on an hourly basis per day. The data shown in
Figure 2 resulted from the summation of the energy consumption of each day of the month.
2.2. DesignBuilder Base Building Energy Model (BBEM) Interface
The DesignBuilder software can be defined as a state-of-the-art graphic interface developed to produce the input file needed for the BBEM calculation. It can be referred to as ‘DesignBuilder BBEM.’ It offers major benefits to energy assessors.
Site-level allows the user to choose the location from the BBEM weather location dropdown menu. Moreover, it enables users to set the orientation of the building in degrees. The building is turned in a clockwise direction concerning the north arrow (this is generally best carried out after the model has been made). The orientation should always be used rather than the manual rotation of the building since it preserves the proper alignment of the axes.
The location used in the computerized modeling is the Queen Alia Airport because the exact building location in Madaba is not available in the software’s location library. Furthermore, the hourly weather data for Queen Alia Airport was utilized for carrying out the annual simulation.
Building creation can be done either with or without the help of a 2-D drawing file created by a CAD system or by having a scan of the building plan. In both cases, 1 or more blocks are entered to define the building geometry.
The extruded block form is possibly the most useful. To create an extrusion block, a perimeter must be drawn using several predefined shapes. After that, the perimeter must be extruded by the required distance. Extrusions can be made either in horizontal planes or vertical ones.
Zone height, which is automatically calculated as the average zone height based on the block geometry, is entered.
DesignBuilder BBEM enables the process of loading building geometry from 2-D drawing files as a DXF file created by a CAD system or scanned images from other sources of building plans. It supports the most common formats. A possible alternative would be to import 3-D “BIM” files as gbXML files.
Areas occupied by both the ground and first floors were considered the same in the geometric model based on the assumption that the added area of the ground floor compensated for the removed area from the first. This assumption is thought to be valid because the building has no below-grade walls.
Both the building outline and internal partitions are needed to draw a building. It is recommended, therefore, to turn off the unwanted layers so that DXF files can be simplified in the CAD environment before exporting the DXF file. Block heights are also of great importance to energy assessors, so they may find it helpful to mark these on the CAD drawing. Furthermore, they could refer to a print of the 2-D drawing file when making a drawing of the building blocks.
The building is partitioned into zones following the BBEM zoning rules. Fewer blocks should be used to create the building, and then each block should be divided into zones by creating partitions between them as depicted by
Figure 3. The building of interest mainly consists of offices, classrooms, and laboratories. Their numbers on each floor are shown in
Table 1.
Each envelope’s zone is defined by the orientation, area, and properties of every physical boundary, including the floor, ceiling, wall, and roof, to calculate the BBEM.
Constructions are treated simply in the BBEM calculation. The U-value, as well as the thermal mass, Km, are needed to complete to the calculation. There are 3 techniques for entry:
Introduction of own values: These values could come from either an independent source or automatic calculations done by DesignBuilder.
Importing a construction from the library: This requires choosing from the lists, including solid (masonry) walls, cavity wall, pitched roof, flat roof, etc. After that, the building regulations which were in effect when the building was constructed, as well as the age bracket into which the building falls, can be selected.
Inference procedures: These call for the selection of the sector, the building regulations which were in use at the time of construction, and a general description offered by the menus.
The lighting in the building was designed according to ASHRAE 90.1 standard and the building ventilation load was calculated according to ASHRAE 62.1 as shown in
Table 3.
The number of occupants was estimated according to survey of building occupants. The occupancy density and operating hours are shown in
Table 4.
A survey was carried out for all the building running-electric equipment as shown in
Table 5.
The building can be divided into 4 thermal zones—classrooms, laboratories, offices, and corridors—in view of the fact that the aforesaid utilities are the only thermally conditioned areas of the building. In addition, they almost account for the heaviest energy consumption of the building by themselves.
The building is supplied with 2 compression chillers with a cooling capacity of 202 tones. One of the chillers also functions as a heat pump. This heat pump is aided by two 200 kW gas boilers that are installed for heating purposes. Moreover, the building is fitted with 3 air handling units to cover its ventilation load. The building ventilation load was calculated according to ASHRAE 62.1 standard.
2.3. Building Management System (BMS)
Our main approach in achieving a thermally adaptive environment is to monitor and control the condition for each room. A building management system was used to help with this task. The actual building contains a building management system (BMS). Data from the BMS were used to calibrate the accuracy of the simulated model.
The BMS is a microprocessor with a controller network installed to monitor and control building services and technical systems such as individual energy consumptions, access control, security, lifts, air-conditioning, lighting, operative temperature, and ventilation. The BMS controls and monitors mechanical and electrical components that control those technical services. Those main components have a primary connection and roots into branches for the building, which also roots to tertiary branches (Supply and return) to every room. Hence, readings at those points could be measured and saved for every room.
The BMS uses real-time monitoring for measuring the temperature of each branch of those components and records them every hour. Graphical trending is also available in the system, which is useful for determining the stability control algorithms and tuning the system, as well as time scheduling of the BMS (i.e., it tells the components when to start and stop). Real lifetime monitoring could also help us inspect if the components are not working on their optimal efficiency, whether the reduced efficiency is caused by a leakage of some type, the component is up for maintenance, or the component needs to be renewed.
The BMS monthly energy consumption is shown in the
Table 6. The readings were obtained from the BMS for each month of 2019. Moreover, those readings were recorded by the BMS on an hourly basis per day, documented the energy consumption of each day of the month.
2.4. Thermal Comfort
The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) Standard 55:2004 defines human thermal comfort as a “condition of mind which expresses satisfaction with the thermal environment.” The thermal sensation of warmth or coldness is highly subjective and is different for every individual. It depends on 4 environmental factors (air temperature, mean radiant temperature, humidity, and air movement), 2 personal factors (metabolic rate and clothing insulation), and 1 psychological factor (expectation) [
35].
Deep normal body temperature in humans is close to 37.2 °C, independent of environmental temperature and higher than the global ambient temperature. Therefore, heat is constantly evacuated through our skin to the surrounding air to compensate for our metabolic dissipation at a rate that maintains thermal equilibrium in the body, i.e., the body’s thermal equilibrium is when the heat generated within the body equals heat loss by the body. Metabolism is the biological chemical transformation within body cells to convert consumed food into energy to run cellular processes with an efficiency of approximately 20%. The generated amount of heat by a human body depends on the number of body cells. Thus, body response is shown in many ways, such as sweating or shivering to maintain the thermal equilibrium in the body. Commonly, 4 different cooling mechanisms occur within the human body through evaporation, radiation, convection, and conduction [
36].
As mentioned before, human comfort is influenced by various factors such as activity, clothing, age, gender, etc. As a result, there is no strict standard that can outline the ultimate atmospheric conditions for comfort for all individuals in the same surroundings. Consequently, ASHRAE (Standard 55) conducted different studies to determine the range of commonly acceptable combinations of temperature and relative humidity in a controlled indoor environment. The results showed that the acceptable range of operative temperature in typical winter office varies from 20–24.5 °C, and the maximum acceptable range of operative temperature in typical summer office varies from 25.5 °C at 60% relative humidity to 26.5 °C at 30% relative humidity. However, the minimum acceptable range of operative temperature is around 23 °C [
35].
Practically, 98% of occupants are thermally satisfied when the temperature and relative humidity integration take place in the comfort zone suggested by ASHRAE, as shown in
Figure 4. Consequently, a person will feel almost exactly as cool at 24 °C and 60% relative humidity as at 26 °C and 30% relative humidity [
36].
Regardless of the location of the building in the world, ASHRAE standards for natural ventilation prove that there is no distinction in the mean preferred temperature for individuals referring to the same outdoor temperature, whereby the domain of acceptable temperature inside any building relies on the outside temperature. The specified temperature range complies with 90% and 80% of the acceptance limits and can reach approximately 30 °C according to ASHRAE 55-2017 standard [
35], as shown in
Figure 5.
The European thermal adaptive comfort standard BS EN 16798-1 is based on ASHRAE 55, and the comfort temperature is calculated in the same way (similar equations but with different coefficients). As there is currently no Australian standard, ASHRAE 55 has been adopted. The adaptive thermal comfort temperature for free-running buildings (the comfort temperature T
c) can be calculated through this equation [
36]:
where T
o is the mean of the outdoor air temperature for the past 30 days (°C), T
c is the thermal neutrality (°C), and T
o is used to find the adaptive thermal comfort 80% acceptability limits inside the building, where at least 80% of the occupants are satisfied with these temperature ranges (80% acceptability limits = Tc ± 3.5 °C) [
36].
In Madaba, Jordan, applying the adaptive thermal comfort model will result in a wider range of temperatures. The thermal comfort temperature zones were expanded to 24 °C and 29 °C in the summer and 19 °C to 25 °C in the winter. These wider ranges would save massive amounts of operational energy if adopted.
Human beings feel comfortable within a range of temperature conditions. Humans have a body temperature of about 37 °C. Even though the human body builds up the heat when it is not moving, which also acts as a parameter in the HVAC load, heat loss must be identical to the rate at which heat is produced. Furthermore, heat gain must be the same as the rate at which heat is lost.
The C-building is a new building built in 2011 with high-technology monitoring and operating systems such as the BMS, which records the temperature inside each room in the building. The temperature is set and maintained between 22–24 °C throughout the year. In theory and in reality, the temperature of 22 °C for heating and 24 °C for cooling varies in some rooms due to the occupant’s behavior in those rooms.
In the simulation, we examined the building’s energy consumption when operated at three different scenarios. The first scenario (1 °C) was the baseline, which was operated at an HVAC temperature of 21 °C for heating and 25 °C for cooling. The second scenario (2 °C) was operated at 2 degrees below the baseline heating temperature and 2 degrees higher the baseline cooling temperature, or 20 °C for heating and 26 °C for cooling. The final scenario (3 °C) awas 3 degrees higher for cooling and 3 degrees lower for heating compared with the base design (19 °C for heating and 27 °C for cooling, which is still within the 80% adaptive acceptability limits).