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Building Energy and IAQ improvement by Coupled Model

The building performances are related to Energy Efficiency and Indoor Air Quality (IAQ). Modeling is one of the best accurate tools for measuring the building performance. Nowadays, Energy Efficiency and IAQ are modeled individually for buildings.
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  IOP Conference Series: Materials Science and Engineering PAPER • OPEN ACCESS Building Energy and IAQ improvement by Coupled Model To cite this article: Seyedmohammadreza Heibati et al   2019 IOP Conf. Ser.: Mater. Sci. Eng.   609  042102 View the article online for updates and enhancements.This content was downloaded from IP address on 24/10/2019 at 05:13  Content from this work may be used under the terms of theCreativeCommonsAttribution 3.0 licence. Any further distributionof this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.Published under licence by IOP Publishing Ltd IAQVECIOP Conf. Series: Materials Science and Engineering  609  (2019) 042102IOP Publishingdoi:10.1088/1757-899X/609/4/042102 1   Building Energy and IAQ improvement by Coupled Model Seyedmohammadreza Heibati 1,* , Wahid Maref  1 , Hamed Saber 2   1 Construction Engineering Department, École de Technologie Supérieure, University of Quebec, Montréal, QC, Canada 2 Mechanical Engineering Department, Jubail University College, Kingdom of Saudi Arabia (KSA) * Abstract. The building performances are related to Energy Efficiency and Indoor Air Quality (IAQ). Modeling is one of the best accurate tools for measuring the building performance. Nowadays, Energy Efficiency and IAQ are modeled individually for buildings. Improvement strategies in both areas are analyzed separately. The fundamental  problem in Energy and IAQ modeling is related to interaction to each other. This problem makes the modeling results unrealistic to the building performance solutions. To avoid this problem, in this current research, Energy and IAQ models are coupled simultaneously as a new co-simulation method. EnergyPlus and CONTAM are used as Energy and IAQ models, respectively. With the co-simulation method, these two models are coupled together. The method is based on the exchange of control variables between both models dynamically and simultaneously. As a result, the exchanges of temperature and air flow variables are corrected. The verification of the new model is based on the comparison of the simulation and analytical results of temperature and air flow variables. In the next step, this new coupling-co-simulation method for a townhouse building is done in two cases: a leaky and a tight building envelopes. Both cases are compared in two types of ventilation systems: infiltration only, and exhaust only. At this point, the simulated air change rates, gas energy use, and particles concentrations are compared for each case. Finally, the necessity of the accuracy of this new method is concluded. 1. Introduction Energy-efficient building design is one of the most important issues in the field of building science. Many discussions on building energy efficiency neglect their potential impacts on IAQ [1]. Limiting the implementation of some energy efficiency technologies and considering their impacts on IAQ shows that current energy design and analysis tools are limited in their capability to model correctly the airflow and IAQ in buildings [2]. Adams et al. [3] used a coupled airflow–thermal model to show that the use of a heat recovery ventilation resulted in 20% energy savings and reduced contaminant levels. Some energy simulation software tools can simulate airflow using multizone airflow models, but the air flow calculation capabilities are often limited and can be difficult to be used [4]. Almost all previous studies have focused on only one aspect, either the building energy conservation or the IAQ [5]. The building energy conservation and IAQ are the two most important themes of an ecological building, both of which cover multidisciplinary issues and, interact with each other [6]. Energy models are used as well as precision tools for building integrated dynamic optimization by using the coupling method for the load and HVAC systems [7, 8]. Modern buildings and their heating, ventilation and air-conditioning systems are now needed not only to improve energy efficiency, but also to meet the growing demand for better comfort performance [9]. In addition, poor indoor comfort has direct effects on user  productivity and indirect effects on building energy efficiency [10]. EnergyPlus is a complete energy simulation program for a multi-zone thermal balance calculation method [11]. Chen et al. used EnergyPlus to simulate the heat, air, and moisture balances and used CHAMPS-Multizone to simulate IAQ [12]. Co-simulation has been used to analyze the interaction between IAQ and energy efficiency [12, 13]. Dols et al used the co-simulation method for the first time between EnergyPlus and CONTAM  IAQVECIOP Conf. Series: Materials Science and Engineering  609  (2019) 042102IOP Publishingdoi:10.1088/1757-899X/609/4/042102 2   [13]. CONTAM predict airflow based on the contaminating concentrations generated in the whole multizone buildings.   CONTAM in order to be able to perform IAQ calculations, it requires indoor temperatures as input data.The air flow temperature is assumed to be in the set-point of the thermostat for IAQ calculation in CONTAM and this is the limitations of the IAQ calculation by using the single models [14]. In this current research, EnergyPlus and CONTAM are used separately to improve energy consumption and IAQ for the leaky and tight buildings with different ventilations. In the next step, using a co-simulation method by development of the coupled EnergyPlus-CONTAM model. The results of each of single and coupled models are analyzed for three scenarios. 2. Methodology This research consists of three main parts. In the first part, how to develop the model using the co-simulation method for coupling between EnergyPlus and CONTAM is investigated. In the second  part, the verification method for developed model is used based on the available methods. At the final  part, application of the model at first by using EnergyPlus and CONTAM programs separately and then with co-simulation method, are analyzed. By using the single and coupled models, air change rates, indoor particles concentrations and gas consumption for a case study townhouse in different scenarios are simulated and then compared. 2.1 Coupling method between EnergyPlus and CONTAM The coupling method is performed based on the energy and mass balances equations. EnergyPlus and CONTAM calculates the energy and mass balances, respectively, according to the Figure 1. Figure 1. Coupling method mechanism for EnergyPlus and CONTAM models. 2.2 Co -  simulation approach between EnergyPlus and CONTAM The co-simulation method, between EnergyPlus and CONTAM, is illustrated in Figure 2. The format of input data to CONTAM is PRJ file (Project file). In addition, the input data to EnergyPlus is formatted as an IDF file (Input data file). The Contam3DExporter tool also can convert the PRJ file into two types of VEF file and XML file   formats. These files are exchanged during co-simulation between both Contam X and EnergyPlus models as shown in Figure 2. These data and control variables are exchanged between the two models by ContamFMU (Functional Mock-up Unit). RST file is simulated for 24 hours in order to synchronize the exchange times at specific time steps. Figure 2. Co-simulation approach for CONTAM and EnergyPlus [13]. 2.3 Verification of coupling method for the developed EnergyPlus-CONTAM model  IAQVECIOP Conf. Series: Materials Science and Engineering  609  (2019) 042102IOP Publishingdoi:10.1088/1757-899X/609/4/042102 3   The model is validated using the Dols et al. verification method [13]. They used the multizone case MZ320 [15] as a test case to verify the coupled Energy-CONTAM model. In this current research, Dols et al. [13] verification method has been used with some changes. The new test case MZ320, with changes are defined according to Figure 3 for zones of A, B and C. Figure 3.  New test case MZ320 for verification of co-simulation method This verification is done in two steps. In the first step, analytical heat balance calculations are performed for the new test case MZ320 based on Equations (1,2 and 3) for the three zones, A, B and C. In these equations, TA, TB and   ̇  are unknown.     ̇  = 0 =    ̇  ,   −     (    −  ) −     ,  (    −  ) −̇  (    −  )   (1)       ̇  = 0 =    ̇  ,   −     (    −  ) −     (    −  ) −     ,  (    −  ) −̇  (    −  )   (2)       ̇  =    ̇  ,   −     (    −  ) −     ,  (    −  ) −̇  (    −  )   (3) By solving these three Equations (1,2 and 3), the values for TA, TB and   ̇ C    are 33.65 ℃, 26.54 and 1361.23 W, respectively. In the second step, the new test case MZ320 is modeled by using the co-simulation method. In this method, calculations of the heat balance between zones are done by EnergyPlus. The calculation of the mass balance between zones is done by Contam X. In the co-simulation method, the MZ320 model as PRJ file is inserted into the Contam X. Three files were  produced by the CONTAM3D exporter. One of them as an IDF file is used for EnergyPlus. Two other files, which include the VEF and XML files, are taken as inputs in to the FMU co-simulation. ContamX calculate the zone mass balance. In zone C, the air handling system is defined with a supply airflow rate of 0.043 (kg/s). Also, an exhaust fan with an airflow rate of 0.021672 (kg/s) is considered. The HVAC AirLoop EnergyPlus heat balance calculation has been selected as a CAV-type HVAC system. The thermal conduction and convection coefficients of the exterior and interior walls and other energy-related components and properties are defined in EnergyPlus. The results of the simulation of TA, TB and   ̇ C   using the EnergyPlus-CONTAM co-simulation method, have been compared with the results of the analytical solutions of Equations (1, 2 and 3) in Table 1. Table 1.  The results of analytical and co-simulation calculations for the new case MZ320.    Results TA(℃)   TB(℃)   TC(℃)   Cooling Load in Zone C (W)   1 Analitical Test Case 33.650 26.540 18.00 1361.228 2 Co-Simulation Test Case 33.656 26.544 18.00 1361.233 In this comparison, the difference between simulated and analytical values is less than 0.006.   Regarding these results, it can be concluded that the co-simulation model has been verified and checked. 2.4 Description of the Case study’s model In this current research, a three-storey townhouse in the city of Montreal is used for simulation. This house comprises four levels. The basement includes gas furnace, gas hot water heater and dryer, all of which are externally ventilated. The area of basement is 24 m 2  and the volume is 72m 3 . The second level  IAQVECIOP Conf. Series: Materials Science and Engineering  609  (2019) 042102IOP Publishingdoi:10.1088/1757-899X/609/4/042102 4   includes a living room, kitchen, bathroom, hall closet and a fireplace in the living room. The area of this level is 35m 2  and the volume is 105m 3 . Third level includes master bedroom, master bedroom closet, master bathroom, bathroom, hall, two bedrooms and a bedroom closet. The area of this level is 37m 2  and the total volume of this level is 111 m 3 . The last level is the attic with area 13 m 2  and the volume is 50 m 3 . The initial input data of the EnergyPlus and CONTAM models are : dimensions and plans of the house, shielding near the building type, size of zones, orientation, geographic location, ambient temperature, envelope material and insulation, weather data files, outdoor particles data, indoor particle sources, cooking source, smoking source, envelope leakage rate, filtration, minimum efficiency reporting value (MERV), wind pressure coefficient and direction, number of occupants, flow paths (HVAC ducts, doors, windows, cracks, etc), ventilation type and other related mechanical - construction systems data. The EnergyPlus calculates the amount of energy consumptions in the whole building based on the energy balance method between building zones and boundary conditions, as well as between interzones.   Systems airflow rate has an important application in the energy transfer between the energy sources and the building multizone or interzones. Airflow rate systems include infiltration and interzone airflow. HVAC systems, as a source of energy in the building boundary condition, uses infiltration for the displacement of energy and zone air temperature.   The CONTAM can calculate the air flow rate system based on the contaminant concentration and other IAQ characteristics, such as occupant exposure for the building multizone and interzone. 3. Results The results of this research include three steps: 1- separate energy and IAQ simulation for the baseline scenario as a reference step, 2- separate energy and IAQ simulation for two scenarios, and, 3- co-simulation of energy-IAQ for improvement of the building performance for scenario 3. Three scenarios are defined for this case study. Each scenario is compared to the baseline scenario (Table 2). Table 2.  Comparison of 3 scenarios with the baseline   Cases Tightening Exhaust Fan Filter Upgrading 1 Baseline no no no 2 Scenario 1 yes no no 3 Scenario 2 no yes no 4 Scenario 3 yes yes yes According to the Table 2, the scenarios are defined based on tightening, exhaust fan and filter upgrading. 3.1 Simulation results of the base case scenario   Simulations on the base case include air change rates, indoor particles concentrations and gas energy consumptions. The results of this simulation are reported based on the third week of each season for all energy and IAQ parameters. For this base case, the air handling system (AHS) is operated with a total volumetric airflow of 0.40 (m 3 /s). Also, in this AHS, the MERV 4 furnace filter is used in one single  pass. The number of residents is 5 people. The sizes of the indoor and outdoor particles for P1, P2, P3, P4 and P5, respectively, are in the range of 0.3 μm to 0.5 μm, 0.5 μm to 1.0 μm, 1.0 μm to 2.5 μm, 2.5 μm to 5.0 μm, 5.0 μm to 10 μm. Indoor particle s generation rates were used based on the Howaed-Reed et al. measurements [16]. Outdoor particle concentrations, measurements performed by Smargiassi et al. in 2005 in four sites in 7 weeks in an urban residential area of Montreal [17]. The results for the air change rates, indoor particles concentrations simulation by CONTAM and gas energy consumptions simulation by EnergyPlus in each season are shown in Figures 4, 5 and 6. 3.2 Simulation results of the scenario 1 to 3 cases   In scenario 1, to reduce the residential energy loss, the exterior envelope is improved to tight envelope.   All exterior envelope leakage area elements are reduced to 45% of the base case. In scenario 2, to reduce indoor particles concentrations, the type of ventilation is improved from infiltration only to exhaust fan only. For this purpose, the exhaust fan with 50 (L/S) air flow rate is used. In scenario 3, the combination of positive effects of tightening and exhaust fan ventilation on the two previous scenarios as well as
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