# Modeling Heat Consumption of an Office Building During COVID-19 Restrictions
###### Abstract  
COVID-19 restricted the number of employees. Operational data showed that traditional methods of modeling heat consumption are not correct anymore. The aim is to model the energy demand of an office building during COVID-19 limitations and showcase improvements after a new controller or suggested alternatives are applied. After an actual heat consumption profile was simulated, energy conservation scenarios were considered: the usage of thermostatic radiator valves (TRVs); accounting impacts of solar radiation and wind; changing mass flow rates based on the indoor temperature; adopting an additional control, changing the temperature setpoint; introducing night and day setbacks. After implementing new design and operational methods, the overheating of indoor spaces was alleviated, and the average indoor temperature was reduced from 23.5 \({}^{\circ}\)C to 20.4 \({}^{\circ}\)C. The annual specific heat consumption decreased to 174 kWh/m\({}^{2}\) (20.2% lower). The methodology ensured thermal comfort and high energy-saving potential. If operating parameters were adjusted, the total saving effect in energy demand was 119.8 MWh, with an energy-saving rate of 19.8%. Employing TRV-related savings and considering thermal inertia provided more stable indoor temperatures and higher energy performance. The minimum saving effect corresponded to the optimal operation and ensuring the indoor environment by considering wind and the maximum one-to-night setbacks. The fluctuations in indoor temperature became smoother. d ARTIC  
1: Thermo and Fluid Dynamics (FLOW), Faculty of Engineering, Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium. 1  
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position. The psychological feelings and the real situation in the world will make these changes in the demand for heat last long in the future. The overall heating demand depends on outdoor temperature, which may rise or drop steeply, for example, every hour. Fortunately, drastic changes in outdoor temperature over a period of 1 h are rare. Additionally, heating systems have implemented algorithms and procedures that protect the heat source (heating node or gas boiler room) from sudden changes in outdoor temperature. Heating systems (especially water systems) have high inertia and are not able to react to rapid changes in outdoor conditions. Heat accumulation and other factors mean that there is no need for a system to react rapidly. However, peaks and valleys are inevitable in any energy consumption profile. Besides weather-related peaks, there are peaks associated with the behavior of occupants (or employees). [PERSON] et al. [2] report that in addition to the morning peak, another peak demand for a space heating (SH) system happens in the late evening at around 21:00. The number of office employees is the second factor affecting heat consumption, i.e., fewer employees are associated with higher energy demand due to lower internal heat gains [3]. This phenomenon is related to the behavior of employees in an office building that lacks automation and control (such as the one used in the case study). When present, employees use doors to enter the buildings, open windows to let some fresh air in, etc. Without employees and contemporary double glazing and plastic window frames, the building is completely airtight, preventing the ingress of cold air and leading to overheating. The present paper discusses what is necessary to avoid that and which effects additional control and automatics may bring. [PERSON] et al. [4] present that some parameters of the indoor environment also correlate with the number of inhabitants or employees. However, the predicted mean vote (PMV) corresponds to indoor thermal comfort rather than indoor temperature. This factor is especially vital to comprehend during the COVID-19 restrictions [3]. The peak demands in the morning and evening are typically due to domestic hot water (DHW) use. This third factor is typical among district heating (DH) systems all over the world [2].