**1. Introduction**

Obsolete equipment, design flaws, and inappropriate use can account for up to 20% of the energy that buildings use over the operation period [1]. Dwellings, offices, educational facilities, and commercial buildings show different consumption patterns. For example, commercial buildings exhibit high energy consumption associated with heating, ventilation, and air conditioning (HVAC) systems and lighting [2]. Office buildings have a high amount of energy use by computers and monitors, while educational buildings have significantly more energy consumption for lighting [3]. Office buildings are likely to have higher cooling demands due to the impact of internal gains from occupants and IT equipment [4]. The European air conditioning (AC) market is essential in raising

awareness about primary energy utilization. Over the last two decades, all members of the European Union (EU) have been committed to increasing the production of renewable energy, decreasing greenhouse gas (GHG) emissions, and reducing the final energy consumption by 20% from 1990 levels by 2020. The goal of reducing the emissions of GHG by 40% by 2030 has been set. Furthermore, the EU members have committed to reducing GHG emissions by 80–95% by 2050, and the fulfillment of the Paris Conference of the Parties 21 agreement will require a further reduction of GHG emissions [5]. In this regard, some studies show that electricity demand for cooling is increasing, especially in colder European countries [6]. If the electricity demand exceeds the projected renewable capacity, the goal of reducing GHG emissions will not be met.

An energy management system (EMS) assures that the building's energy demand is accomplished without compromising the air quality and comfort levels of its occupants [7]. The EMS can collect measurements at a specified time interval at designated measurement points. The accurate and diverse data, deployment without affecting the building operation, communication protocol, and cost influence the selection of the EMS [8]. Engineers tend to overestimate the internal heat gains in office buildings, which results in the specification of cooling systems that exceed the needed capacity. As a result, there is an energy waste over long periods of inefficient operation [9,10]. The Energy Consumption Guide (ECG) shows patterns and benchmarks for electricity consumption in office buildings [11]. Energy consumption schedules, occupants' habits, and the diversity of electric loads have a significant impact on office building energy behavior [12,13]. An energy management system allows owners to understand building performance, improve energy efficiency, and take appropriate actions [14,15].

Power load density is used to assess expected peak power demand, taking into account internal heat gains [16,17]. The building envelope materials contribute decisively to reducing the heating and cooling loads. Windows and curtain walls play a crucial role in the energy efficiency of office buildings due to solar heat gains. Although solar radiation may help reduce heating loads in the cold season, summer heat gains have to be avoided [18,19]. In this regard, the extensive use of glass in facades in office buildings has led to an 8.7% increase in the AC market in Europe over the last decade, especially in Mediterranean countries [20,21]. Despite the growth of the market, other factors like the increasing price of electricity in the European Union (17% from 2008 to 2019) [22] and new government regulations have forced manufactures to develop energy-efficient products, such as inverter technologies and new refrigerants [23]. The energy performance of heating and AC systems is measured by the energy efficiency ratio (EER) in the cooling mode and the coefficient of performance (COP) in the heating mode. The seasonal energy efficiency ratio and the seasonal coefficient of performance (SEER, SCOP) designate the total heat supplied or removed from areas (Qheat/cold, season) divided by the total work input over the same period (Welectricity, season) [24]. By product type, split systems, coupled with air-to-air heat pumps, account for the majority of AC units per type [25]. Air-to-water and water-to-water heat pumps can be coupled with fan coil units (FCUs) and radiant panels in walls, floors, and ceilings. The EER and COP of heat pumps depend on the source and load side temperatures, so assessing the energy performance of each type requires analyzing the outdoor and indoor operating temperatures [26].

When it comes to defining thermal comfort conditions, six main factors must be taken into account: metabolic rate, clothing insulation, air temperature, radiant temperature, airspeed, and humidity [27]. Fanger's Predicted Mean Vote (PMV) method was developed to consider the different variables that influence the comfort assessment in a working environment [28,29]. The international organization for standardization document ISO 7726 defined local thermal discomfort as the thermal dissatisfaction caused by unwanted cooling or heating of one particular part of the body. It mainly affects people developing light sedentary activities [30]. The mean radiant temperature (MRT) has a strong influence on human thermal comfort because occupant bodies transfers heat to hot or cold surfaces [31]. In office buildings with convective heating and cooling systems, such as split units, and facades with extensive glazing, users experience a lack of comfort caused by the inhomogeneity in indoor surfaces and air temperatures [32]. For example, windows with high thermal transmittance and without Low-E coatings can lead to high radiant temperature asymmetry and the local dissatisfaction of some body

parts [33]. An effective way to improve the comfort conditions in these buildings would be to use temperature-controlled surfaces or radiant panels as the principal source of sensible cooling and heating in the conditioned space. Radiant panels provide a comfortable indoor environment without lowering the room air's moisture content. Occupants in an area heated or cooled by radiant panels are comfortable at lower air temperatures in winter and higher air temperatures in summer. Indoor partitions and facades with Water-Flow Glazing (WFG) are considered active radiant panels that control their temperature by circulating water, and can be used to control the surface temperatures and provide an acceptable thermal environment [34]. In facades exposed to solar radiation, the water flows between two glass panes and captures most of the solar infrared radiation, and the visible component enters the building [35]. Since the WFG is a dynamic envelope, the solar heat transmitted through the material depends on the flow rate. When the water flows, the transmitted solar heat is low, and when the water flow stops, the solar radiation enters the building [36]. In interior partitions, WFG panels can supply the needed power at a rate of 120 W/m<sup>2</sup> if the difference between the circulating water and the indoor air temperature is 10 ◦C [37].

This paper focused on assessing the performance of WFG envelopes in commercial buildings by analyzing power demand patterns through measured data obtained from a testing facility. Hence, to achieve this goal, it was essential to: (i) validate the energy management system to enhance the thermal performance of the building, (ii) estimate the final energy consumption of the office space in summer and winter conditions, and (iii) evaluate the comfort conditions and the influence of the mean radiant temperature in the Predicted Mean Vote over the office space working hours.
