In the last years in European countries important measures were taken in order to reduce the energy need of buildings. Nevertheless the energy need for cooling of buildings is rising. In most cases, to assure the required operative temperature, air conditioning systems are installed. Consequently, in summer period the power networks of different European countries are overloaded. In order to determine the effects of glazed area orientation, air change rate and thermal mass on the indoor air temperature, at the University of Debrecen the PASSOL laboratory was built. Measurements were performed from 2009 to 2013. Using the methodology given by EN ISO 13790 the variation of indoor temperature was calculated and the theoretical values were compared with values obtained from measurements. The indoor temperature variation and the energy need for cooling was analysed for different building structures, different orientations of the glazed area and air change rates. The calculations have proven that the energy need for cooling can be reduced even to 25% of the thermal mass and the air change rate are chosen properly.

Abstract:As it is known that nowadays, reduction of the heating energy loss of buildings is achieved mainly by thermal insulation. This is one of the most important objectives of buildings constructions and retrofitting of buildings. Therefore research, calculation and simulation on the energy efficiency of buildings are of great importance. In this paper we give an expansive presentation about the measurements of the thermal conductivity, heat flux and thermal resistance of individual insulation materials as well as in-built wall constructions executed in our laboratory. Thermal diffusion coefficients and wall delaying ability of the systems will be given resulting from the measurements. First of all, thermal conductivity measurement results of individual insulation materials achieved by a Holometrix type Heat flow Meter (HFM) will be presented. Afterwards, two different steady-state methods for measuring thermal resistance of wall structures (Calibration hot box method (CC) and Heat Flux measurements by Hukseflux (HF) apparatus) will be introduced. These measurements were accomplished through either an inbuilt plaster/brick/plaster wall construction insulated internally at the first time and later externally with different materials. The main target of this paper is the presented theoretical procedure for the estimation of the retardation time of wall structures. Furthermore in this publication the determination of thermal performance of Expanded Polystyrene Insulation (EPS) applied to walls in building constructions can also be found. Moreover numerical predictions for thermal resistance are presented. Besides, infrared thermographs were used to visualise the insulation ability of the layer structures.2

As a result of COVID-19, many office buildings around the world have downsized their employees, but the comfort parameters in the building had to be kept. The facilities operation rearranged the workstations to keep physical distance and placed plexiglass sheets on the desks for physical protection. A series of measurements have been carried out with workstation set-ups to examine the fresh air rate in the occupied zone. The effect of plexiglass sheets placed on the desks was also examined to see how it changes the airflow pattern in the occupied zone. As the sheets act as a barrier, the primary air does not reach the occupied zone, therefore, the fresh air rate is less. To modify the properties of the ceiling diffusers a new air-ventilation service element was developed. This attachment allows modifying the properties of the ceiling diffusers. Simulations were made at the relevant zones to validate the measurements. Based on design software, the fresh air ratio for a standard ceiling swirl diffuser is 2.46 v% (volume percentage). A numerical model was used to show the fresh air ratio with the system elements for the two different table arrangements, which were 18.3 v% and 21.4 v%, respectively.

Over the last several years, the energy used for air conditioning in buildings increased in most European countries because of the high heat loads during the summer and the occupants’ increased comfort needs. The aim of our research was to determine the incident solar radiation on horizontal and vertical surfaces and to investigate the heat loads of buildings with different orientations of the glazed areas and different thermal masses in the building structures. Using the measured hourly global radiation data for the years 2009–2013, the diffuse and direct incident solar radiation was determined for the horizontal and vertical surfaces. A statistical analysis of the daily energy yield from solar radiation and the daily mean outdoor temperatures was conducted. The number of symmetric and asymmetric days was determined for torrid days. Using the methodology provided by standard EN ISO 13790:2008, the cooling energy demand and daily energy need for cooling was determined and evaluated for representative days of the analyzed years.

In recent years, because of the high heat loads during the summer period and increased comfort needs of occupants, the energy used for the air conditioning of buildings has increased in most European countries. Choosing circumspectly the building materials and the transparent areas on the facades, proper indoor thermal conditions can be assured without cooling the fresh air. However, in this case the ventilated air flow has to be controlled properly. The aim of our research was to investigate the effects of thermal mass and air change rate on the allowable transparent area for different orientations of facades. Measurements were performed in a special rotating laboratory to determine the relation between thermal mass, incident radiation and indoor temperature. The incident solar radiation was determined for vertical surfaces using the measured global radiation data from 2009-2013. Measurements were carried out to determine the effect of stored heat on the internal air temperature excluding the effect of air change rate and solar radiation. Using the methodology given by standard EN ISO 13790, the allowable transparent area was determined assuming different building materials and air change rates. Based on calculations effectuated on 688 building models, it was proved that there is a linear relation between allowable transparent area and air change rate. Keywordsair change rate, building materials, solar gains, thermal comfort, thermal mass IntroductionHighlights  the effects of thermal mass on the operative temperature was investigated  the relation between allowable transparent area and thermal mass was analysed  the relation between thermal mass and air change rate was analysed  688 building models were investigated