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Radiant heating and cooling systems have been proven to be an energy-efficient and resource-effective heating and cooling solution for buildings. One of the key features of radiant systems is the possibility of activating and controlling the thermal mass. This feature allows spreading the heat removal from indoor spaces over a longer period, compared to more conventional systems e.g., air-conditioning. This feature of radiant systems could be particularly beneficial under heat wave and power outage events. The present study investigated the performance of Thermally Active Building Systems (TABS) and Packaged Terminal Air Conditioners (PTAC) in terms of controlling indoor temperatures under future typical weather files, and under future heat wave and power outage events. The simulations were carried out for Copenhagen, Denmark. For future typical meteorological years, TABS performed better with heavyweight construction, but PTAC had little influence from the construction type. During heat waves, both systems were able to maintain a generally comfortable temperature range but with a slightly overall higher temperature. When a heat wave and power outage occurred at the same time, the cases with heavyweight construction had lower temperatures regardless of the cooling system. With TABS and heavyweight construction, the room temperature was maintained within the comfort range of 26°C for 16 hours after the heat wave and power outage started. After the power outage was over, TABS with heavyweight construction was able to reduce the room temperature to the comfort condition of 26°C faster than PTAC by 18 – 71 hours. Results obtained from this initial set of simulations suggest TABS could be a better solution than PTAC in terms of its resiliency to heat waves and power outages although both systems could have different advantages depending on the operation, building type and building use.

Thermal comfort affects the sleep quality and well-being of people. The effect of a ventilated mattress (VM with integrated localized heating on providing the necessary thermal conditions for comfort in the bed-microenvironment was studied. The VM has an exhaust opening located under the feet of a lying person. Air is sucked and transported inside the mattress by a small fan connected to the mattress. The benefit of using such a mattress is that it sucks and removes body-emitted bio-effluents, which prevents the pollutants to spread in the room. The air movement inside the mattress provides cooling to the body, which makes the bed micro-environment comfortable during the cooling season but may cause discomfort during the heating season. Therefore, the VM was further developed by implementing local heating. Full-scale experiments were performed in a climate chamber furnished with a single bed equipped with the VM. A full-size thermal manikin was used to simulate a person lying in the bed. The performance of the VM with regard to the provided body heating/cooling was studied at room air temperatures of 19, 23, and 28 ℃. The control of the thermal conditions in the bed-microenvironment was tested when the VM was operating at different airflow rates and local heating power. A reference condition at 23 ℃ without the VM in operation was assumed to provide thermal comfort in the bed. The performance of the VM was evaluated based on a comparison of the body dry heat flux from the segments and the whole body of the thermal manikin obtained with the VM in operation and during the reference condition. The results show that it was possible to achieve the same body heat flux at all studied room temperatures using the VM with localized heating as in the reference condition. The use of the VM combined with localized heating with control based on the individual needs of the user can be an efficient method for providing thermal comfort in a bed at a wide range of room air temperatur

Bioeffluents emitted from person lying down in bed can be removed by ventilated mattress (VM) before mixing with the room air. VM is designed to suck air through an exhaust opening located near the feet and move the sucked air inside the mattress. The air moves through the whole mattress and is removed to the exhaust or cleaned and discharged back to the room. The VM can change the thermal conditions in the bed micro-environment and provide uncomfortable local cooling of the person in the bed. Therefore, the design of the ventilated mattress is further improved by incorporating local heating. The response of people to the bed thermal environment generated by the mattress was studied at three room air temperatures – 19°C, 23°C and 28°C. 30 human subjects (15 males, 15 females) of age 20 - 29 years old and body mass index in the range 18 - 27 were exposed to the bed thermal environment provided by the VM. The subjects were covered with a thin duvet (2.9 clo) at room temperature 19°C, a double cotton sheet at 23°C and a single cotton sheet was used at 28°C. The subjects were dressed with pajama (short-sleeve shirt, shorts) and underwear. Thermal sensation assessment was collected through standardized questionnaires. The subjects answered questions regarding their whole body thermal sensation and local thermal sensation of separate body parts including face, head, neck, chest, back, arms, hands, thighs, lower legs, and feet. The bed thermal micro-environment was adjusted by the exhaust flow rate through the ventilated mattress and the localized heating depending on the acceptability of the subjects’ thermal sensation collected every 7 minutes. The results show that the applied control of the bed thermal environment increased the acceptability of the whole body thermal sensation votes and the risk of local cold discomfort (especially on the feet and hands) decreased over time. Local heating at the feet will be needed to achieve thermal comfort in room temperatures below

The annual energy-saving potential and IAQ improvement by use of a hospital bed-integrated pollution source control, a ventilated mattress (VM) and local bed ventilation (LBV), was studied. The VM is designed to capture in the bed and exhaust human body bio-effluents. The LBV is supplies clean air close to the breathing zone of the patient in bed and exhausts the polluted (might be infected) exhaled air from the patient before it is mixed with the room air. Exhaled air removal efficiency of the LBV were assumed at 40%, 60% and 80%. Thus, the risk of cross-infection was reduced. Energy use simulations were performed by IDA-ICE software. Intake fraction was used to indirectly assess the risk of cross-infection. Three scenarios were simulated to evaluate the energy-saving potential of the source control methods: 1) a double-patient room (none of patients is infected) using the VM and constant air volume ventilation (CAV), 2) a double-patient room (either one or two patients is infected) using the VM and CAV and 3) a double-patient room (either one or two patients is infected) using the VM, the LBV and CAV. The results reveal that using the VM and the LBV at decreased background ventilation rate can be an effective method for reducing the energy costs needed for hospital wards. Depending on the operation of the VM and the LBV, the energy-saving was between 1880 kWh and 67964 kWh. The annual energy-saving was up to 83.6% when the ward with two infected patients using LBV at 80% exhaled air removal efficiency and CAV at a reduced ventilation rate, compared with the reference cases of only CAV operating at 12 air changes per hour (ACH).

Personal comfort models could be used for the development of automatic controls for personal environmental comfort systems (PECS). These models often use indoor environment and physiological indicators as attributes for estimating the subjective response of occupants. Traditional indoor thermal environment research and standardization recommend 7-point scales for thermal comfort or thermal sensation estimation. However, many studies apply transformations to the response, thus oversimplifying the scales and generating controversy. The aim of this study is to determine the relevance of different indicators for the development of personal comfort models while investigating the implications and resulting model accuracy when using different thermal sensation scale discretization. Two simple machine learning algorithms, namely logistic regression and Naïve Bayes, were used in a multi-class setting to predict the overall thermal sensation of individual subjects when occupying a heated or cooled chair in steady state conditions. Multiple models were generated depending on the variables included in the feature set. Additionally, two response vectors were generated based on the thermal sensation vote, a three class and a seven class one, the latter being generated by further discretizing the hot and cold spectrum of thermal sensation. Both models performed better than a random guess at identifying thermal sensation classes and reached accuracies of up to 72% when predicting the overall thermal sensation of people using PECS. Including information of the PECS operation in the model, i.e. seat temperature, increased the prediction accuracy by up to 5%. The overall accuracy was higher when using three classes for the thermal response, as implementing seven classes led to a decrease of up to 21 percentage points. Nevertheless, the latter provided a finer adjustment without affecting the model’s ability to distinguish between the cold and hot spectrum, which may be an advantage fo

Hydronic radiant ceiling panels use a chilled surface to cool a room, and their cooling capacity is normally measured in a certified test chamber. However, current measurement standards calculate the cooling capacity of a panel based on the heat carried by the circulating water, which is the sum of the heat extraction from the room and plenum. Thus, sizing the radiant system based on the cooling capacity of the panels may result in an undersized system. In this study, a series of test chamber measurements and field measurements were conducted to quantify and empirically predict the proportion of the heat extracted from the room-side to the total heat extracted by the radiant panel. The cooling capacity of suspended radiant ceiling panels was first measured in a certified test chamber, with the temperature difference between the room and plenum as the main parameter. Within the tested temperature range (plenum temperature of 24 – 28 °C, room temperature of 26 °C), the heat extracted from the room side was 77 – 92 % when the panels were insulated and decreased to 46 – 71% when they were not insulated. A simplified, empirical approach for estimating the heat extraction at both sides of the panel was proposed based on the obtained results. A field measurement was then conducted to examine the validity of the proposed methodology. Measurements were conducted in an office building located in Japan, which was equipped with radiant ceiling panels of the same type as the ones tested in the chamber measurements. Heat flux sensors were placed at both the room and plenum sides of a single radiant panel to obtain the proportion of heat extraction from the room-side. The measured room and plenum temperatures were used as input for the prediction of the room-side heat extraction ratio, and the average error of the predicted heat flux was 6%, confirming the validity of the proposed methodology.

There is good evidence supporting the airborne transmission of many respiratory viruses (measles, influenza A, human rhinovirus and the novel SARS-CoV-2). Relative humidity (RH) is an important factor in understanding airborne transmission as it may impact both airborne survival, inactivation by biological decay, and the gravitational settling of the virus-laden droplets. This study aimed to estimate and compare the impact of indoor relative humidity on the airborne infection risk caused by these viruses using a novel modified version of the Wells-Riley model. To gain insights into the mechanisms by which relative humidity might impact airborne transmission infection risk, we modeled the size distribution and dynamics of airborne viruses emitted from a speaking person in a typical residential setting over a relative humidity (RH) range of 20–80% at a temperature of 20-21 °C. Besides the size transformation of virus-containing droplets due to evaporation and then removal by gravitational settling, the modified model also considers the removal mechanism by ventilation. The direction and magnitude of RH impact depended on the respiratory virus. Measles showed a highly significant RH impact that was as strong as the ventilation impact, as the infection risk was roughly the same at RH of 13.5 % and 6 ACH compared to a higher RH of 70 % and 0.5 ACH. For other viruses, ventilation dominated over RH. In the case of SARS-CoV-2, a very high RH of 83.5% was needed to reduce the infection risk. For rhinovirus, however, the high RH of 80% increased the infection risk. Within the acceptable range of RH of 20-50% indoors, our modeling showed that RH had practically no impact for SARS-CoV-2 and rhinovirus, while the upper RH significantly reduced the infection risk of influenza A at the lowest ventilation rate of 0.5 ACH. This relative impact of RH on infection risk became very weak at higher ventilation rates of 2-6 ACH independently of the virus types (except measles). In conclus

Personalized Environmental Control Systems (PECS) condition the immediate surrounding of occupants in contrast to conventional HVAC systems. PECS have several advantages including allowing occupants to adjust their immediate surroundings according to their preferences, which could improve their satisfaction with the indoor environment, which may lead to higher productivity. PECS can also lead to noticeable energy savings, if implemented effectively in buildings. The present study explains the development process and initial testing of a novel PECS. The PECS had heating, cooling, and ventilation functions, together with the possibility of adjusting lighting color and brightness. Ventilation and cooling were provided from a desktop air terminal device, and heating was provided by a curved panel covering the lower body from the thigh to the lower leg of a seated occupant. A thermal manikin was used to quantify the heating and cooling performance of the different versions of the PECS. The most recent prototype was able to provide a cooling effect up to 6 K (calculated by the manikin-based equivalent temperature difference) to the left side of the face, and a heating effect of up to 5 K to the left and right thighs. The cooling and heating effect of the whole body was up to 0.3 K and 1.3 K, respectively. A Peltier element was introduced to lower the supply air temperature from the PECS, but had limited effect on the cooling effect despite the large increase in power use. When implementing a Peltier element in PECS, the generated waste heat must be handled so that it does not interfere with the cooling.

Diffuse ceiling ventilation utilizes the entire ceiling surface to distribute airflow to rooms. The air seeps via perforations, often present in acoustic ceilings, from the pressurized plenum to the occupied zone below. In the literature, this concept has proven superior in terms of draught, even for quite high airflow rates and sub-temperatures. However, documentation of practical installations followed by measurements campaigns and in-depth analyses of the concept, are rare. Consequently, we present a study to showcase the performance of the installation under rather extreme conditions: air change rate of 20 h-1 and supply temperature 3- 4°C below room temperature. The corresponding cooling was 56-74 W//m2. The investigated room was 165m² and 2.75m high. Numerous computers and TV screens caused significant heat loads, as well as the large windows on 3 facades of the room (West, North, East). The ventilation, equipped with a cooling coil, supplied 9200 m³/h to maintain the temperature in the room. The airspeeds and temperatures were measured at 7 different heights (from 0.1m to 2.4m) in 26 positions. The results showed an even distribution of the temperature in the room with measurements between 23 and 26˚C and an average temperature gradient of 0.33˚C/m (max 0.8˚C/m) while in the plenum the difference of temperature was 1.5˚C between the inlet and the opposite corner. The airspeeds were on average between 0.11 m/s and 0.17 m/s with the highest values at the ankle level. Half of the logged points had Draught Rate (DR) below 10% and all positions were below 20% except one. The airspeed exceeded 0.2m/s in less than 9% of the measurements. For comparison, we discuss the implications of using ceiling swirl diffusers or displacement ventilation in the same context.

Detailed simulations of HVAC systems play a crucial role in creating 1:1 digital twins of buildings and their systems. In particular, detailed models of hydronic systems are essential for fault detection of building services and control optimization. However, modeling HVAC systems is labour intensive due to the components and connections that one must create based on drawings or models. Creating the HVAC simulation models from BIM data eases the modelling burden, simplifying the creation of digital twins. Straight-forward HVAC simulations can aid the design process. Instead of prescriptive design based on the worst-case conditions, simulations enable performance-based design with partial-loads and dynamic behaviour. This paper presents a preliminary tool using BIM data to create and simulate models of heating systems. The tool uses a central BIM data platform with a dedicated data format – defining components and their relations in a database. Python scripts apply model templates to create heating system models in the Modelica language. The tool simulates the models in Dymola, while Python scripts read and parse the results to the database for visualization and analysis. The tool efficiently simulated a small heating system and obtained results for the return temperatures of several loops.

The TAIL rating scheme was developed to assess indoor environmental quality (IEQ) in offices and hotels undergoing deep renovation and was recently extended by the PredicTAIL method allowing prediction of IEQ through modeling. TAIL provides the methodology for rating the quality of the thermal, acoustic, and luminous environments, the indoor air quality, and the overall quality of the indoor environment. The present work is an extension of the use of TAIL rating scheme for school classrooms to provide necessary information for effective actions and mitigation measures to improve classroom IEQ. The TAIL was invented by examining the literature and certification schemes to identify the parameters that characterize IEQ in offices and hotels; 12 parameters were selected. A similarly pragmatic approach is followed when developing the TAIL for schools. The literature published after 2010 was surveyed to identify papers presenting measurements of IEQ in classrooms in Europe, the USA, and Australia; 75 papers were identified. Besides the 12 parameters already included in TAIL, the studies also used other parameters to characterize classroom IEQ. These parameters will be evaluated for their importance for the teaching, learning, and well-being of pupils, as well as measuring complexity, among others. Based on this assessment, the relevant parameters will be selected for inclusion in the TAIL rating for schools. The selection will be assisted using the measurements from the extensive campaign organized by the Indoor Air Quality Observatory in 308 schools and 602 classrooms in France; some of these data will be used to assess the efficacy of the TAIL for schools indicator. The relationships between the newly developed TAIL for schools, the teacher’s perceptions of indoor environmental quality, and detailed building characteristics will be studied.

Heat pumps (HPs) are an excellent solution to supply heating and cooling for indoor space conditioning and domestic hot water (DHW) production. Conventional HPs are typically electrically driven and operate with a vapour-compression thermodynamic cycle of refrigerant fluid to transfer heat from a cold source to a warmer sink. This mature technology is cost-effective and achieves appreciable coefficients of performance (COP). The HP market demand is driven up by the urge to improve the energy efficiency of building heating systems coupled with the increase of global cooling needs for air-conditioning. Unfortunately, the refrigerants used in current conventional HPs can have large greenhouse or ozone-depletion effect. Alternative gaseous refrigerants have been identified but they present some issues regarding toxicity, flammability, explosivity, low energy efficiency or high cost. However, several non-vapour-compression HP technologies have been invented and could be promising alternatives to conventional systems, with potential for higher COP and without the aforementioned refrigerant drawbacks. Among those, the systems based on the so-called “caloric effects” of solid-state refrigerants are gaining a lot of attention. The caloric effects are large entropy and adiabatic temperature changes caused by the application or removal of an external field in certain specific solid materials. There are 4 main caloric effects: magnetocaloric, elastocaloric, electrocaloric and barocaloric. Each of them is characterized by the nature of the field and the response that induces the entropy and adiabatic temperature change: variation of the magnetic field, uniaxial mechanical stress, electrical field or hydrostatic pressure, respectively. A HP cycle can be based on these caloric effects and several heating/cooling prototypes were developed and tested over the last few decades. Although not mature technologies yet, some of these caloric systems are well suited to become new efficient