The authors studied the impact of indoor air humidity in the range of 60% to 90% on building user perception in the temperature range of 26 to 28 °C. The research thesis was put forward that the impact of humidity on indoor air quality dissatisfaction of building users in a warm and humid indoor environment is greater than that indicated in thermal comfort models. The presented experiment examined the indoor air quality perception of n = 28 subjects in the test chamber of a nearly zero energy building under ten environmental conditions, together with a thermal comfort assessment. The authors developed an experimental relation for predicting building users’ satisfaction based on the Weber–Fechner law, where the predicted percentage of dissatisfied users (PD) is determined by means of air enthalpy (h), PD = f(h). The obtained results confirmed the sated thesis. Additionally, the intersection points of the experimental function and isotherms resulting from the Fanger model are presented, where the thermal comfort assessment starts to indicate lower user dissatisfaction results than experimental values. The authors recommend the experimental equation for humid air enthalpies in the range of 50 to 90 kJ/kg. The indoor air quality assessment based on the enthalpy value is simple and can be used to determine the overall Indoor Environmental Quality index of a building (IEQ_index).

Improving the energy efficiency of buildings is among the most urgent social development tasks due to the scale of energy consumption in this industry. At the same time, it is essential to meet high requirements for indoor environmental quality and thermal comfort. The issue of overheating is most often analysed in summer but it also occurs in transition seasons, when the cooling systems do not operate. The paper attempts to evaluate the effectiveness of external mobile shading elements on the microclimate of rooms with large glazed areas in the transition season. Passive solutions, such as shading elements, which limit the increase of indoor temperature, do not always allow the acquisition and maintenance of comfortable solutions for the duration of the season, as demonstrated by the authors. Temporary cooling of the rooms may be necessary to maintain comfortable conditions for the users, or other solutions should be devised to improve comfort (e.g., reduction of clothing insulation characteristics). The novelty of the study consists in the analysis of comfort in a “nearly zero energy consumption” building (NZEB) during a period not analyzed by other scientists. This is a transition period during which heating/cooling systems do not operate. The research task set by the authors involved the assessment of the possibility to reduce office space overheating in the transition season (spring) by using external shading equipment in rooms with large glazed areas. An additional research task aimed at checking the extent to which user behaviour, such as reduction in clothing insulation characteristics, can improve comfort in overheated rooms. The results of the tests reveal that the difference in the ambient air temperature between a room with external venetian blinds and an identical room with no venetian blinds in the transition season, i.e., from 27 March to 6 April 2017, ranged from 12.3 to 2.1 °C. The use of a shading system (external venetian blinds positioned at an angle of 45°) reduced the number of discomfort hours by 92% (during working hours) compared to the room without external venetian blinds. A reduction in the thermal insulation of the clothes worn by people working in the room with no venetian blinds helped to reduce the number of discomfort hours by 31%.

The use of phase change materials (PCM) in different building applications is a hot topic in today’s research and development activities. Numerous experimental tests confirmed that the hysteresis of the phase change process has a noticeable effect on heat accumulation in PCM. The authors are trying to answer the question of whether the neglecting of hysteresis or the impact of the speed of phase transformation processes reduce the accuracy of the simulation. The analysis was performed for a model building, created to validate the energy calculations. It was also important to conduct simulations for the polish climatic conditions. The calculations were conducted for three variants of materials. In addition, in the case of models containing layers with PCM, calculations were made both taking into account, as well as excluding material hysteresis in the calculations. In the analyzed examples, after taking into account hysteresis in the calculations, the period of time when surface temperature is below the phase change temperature of the materials decreased by 10.6% and 29.4% between 01 June to 30 September, for the options with PCM boards and Dupont boards, respectively. Significant differences in surface temperature were also observed. The effects of neglecting, even relatively small hysteresis, in the calculations are noticeable and can lead to significant errors in the calculation.

In order to design and optimize building materials containing phase changing material (PCM), it is important to accurately characterize the thermal properties of these composites: the enthalpy curve and its hysteresis. This paper presents the initial tests of these properties for a composite panel: gypsum plasterboard with an evenly distributed layer of PCM. Performance testing of the selected material was carried out by means of the dynamic method. This method (dynamic heat flow meter apparatus (DHFMA)) involves the measurement of non-stationary heat flow to determine the stored energy (enthalpy change) as a function of temperature using a stationary heat flow measurement apparatus (HFMA). This method allows for the measurement of the sensible and latent heat capacity of the products containing phase change material. In addition to presenting the obtained results, the study will discuss the practical aspects of this test method, recently introduced in the standard ASTM C 1784-20. The preliminary experiments described in the article were aimed at learning a new research technique, determining the required conditions for conducting research and the capabilities of the possessed apparatus in this regard.

There are currently trends in the world to transfer and adapt traditional solutions to contemporary needs. This applies, inter alia, to mobile shelters used by nomadic peoples. The article is devoted to the research on the quality of internal air in the yurt and the possibilities of its adaptation to high contemporary quality and environmental requirements, while maintaining its characteristic sustainable values. The tested traditional Mongolian yurt was moved from the dry and cold climate of the Asian steppe to the temperate climate of Central Europe and has been significantly modified. The outer shell materials have been changed, replacing natural materials with modern tight insulating foils. The wood-fired stove has been replaced with an electric heater and the roof opening has been firmly closed. All of these modifications resulted in far-reaching changes in the quality of the internal environment in the yurt. The conducted measurements and simulations of CO₂ concentration in the modified yurt proved that the efficiency of ventilation system is not sufficient and that the air quality is very poor (even for a single user). In the case of a larger number of users, the concentration of CO₂ has already reached a level that was dangerous to health. The simplest method of improving the air quality in the yurt is its careful unsealing to the required level. Striving for a low energy demand, however, would require a completely different approach (for example, in the form of forced ventilation with a heat recovery unit, ultimately powered with a PV array). Such a solution is very different from the traditional yurt model but is close to modern expectations and environmental requirements.

The article presents the results of research on the thermal and mechanical properties of concrete slabs with pumice aggregate soaked with dodecanol (duodecyl alcohol), i.e. an organic material that changes its phase at a temperature +24oC. It is possible to implement this type of integration of phase-change material with a typical building material in any precast concrete plant without additional expenditure on equipment and without technically difficult vacuum impregnation. The use of concrete panels with a 4% mass content of PCM as the internal cladding of building components allows for a significant change in the internal heat capacity of the building and, consequently, a change in the thermal properties of the buildings. In a very simple modeled object with a light wooden structure, intensively cooled during the night, the influence of the type of internal cladding on the internal thermal comfort in the summer was analyzed. It has been shown that the cladding in the form of a concrete PCM panels with a thickness of 3.5 cm, compared to a standard gypsum board, effectively limits the temperature increase and significantly shortens the duration of discomfort conditions. The maximum daily fluctuation of operative temperature during summer, which was approximately 15 K in a lightweight building, has been limited to approximately 8 K thanks to PCM concrete panels. The difference in the average values for the entire simulation period, equal to 1.76 K, does not fully illustrate the improvement of thermal conditions during periods of high heat load. Reduction of the plate thickness to 2 cm only slightly worsened the conditions in the analyzed facility and can be treated as a reasonable compromise solution for lightweight construction technologies. In the case of an unreasonably large window area, regardless of the actual space thermal capacity, it is not possible to obtain the acceptable conditions inside only by means of the passive methods.