The purpose of the article was to present information on heat recovery in ventilation systems and to highlight what has not been sufficiently researched in this regard. A lot of information can be found on methods and exchangers for heat recovery in centralized systems. Decentralized, façade systems for cyclical supply and exhaust air have not been sufficiently researched. It is known that these devices are sensitive to the influence of wind and temperature, hence heat recovery may be ineffective in their case. The literature describes the aspect of heat recovery depending on the location in climatic zones, depending on the number of degree days (HDD). Attention was also paid to the risk of freezing of heat recovery exchangers. The literature review also showed the lack of a universal method for assessing heat recovery exchangers and the method of their selection depending on the climate.

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Abstract. The paper presents the thermal resistance characteristics of walls with multilayer reflective insulation. The tests have been performed using a heat flow meter to determine the resistivity of the layers simulating partition walls in buildings. A modification of the structure has also been proposed and analysed with a view to increase the thermal resistance and, consequently, reduce the heat flux transferred through the walls. Consequently, walls produced with layers that ensure higher thermal insulation lead to better thermal performance properties of the whole buildings, which reduce heating/cooling costs throughout the year.

Many building are characterized by insufficient air exchange, which may result in the symptoms of sick building syndrome (SBS). A large number of existing buildings are equipped with natural ventilation, whose work is disturbed by activities going to energy-saving. The thermomodernization activities are about mounting new sealed windows and laying thermal isolation, which reduces the amount of infiltrating/exfiltrating air. In many cases, the mechanical ventilation cannot be used due to a lack of a place in building or architectural and construction requirements. One of the solutions to improve the indoor microclimate is the decentralized façade ventilation. In the article, the internal air parameters in an office room equipped with decentralized façade ventilation device were analyzed. The room was equipped with a decentralized façade unit, which cyclically supplied and removed air from the room. The time of the supply/exhaust was changed to 2 min, 4 min, and 10 min. The temperature and the humidity of the indoor air and the outdoor air and the concentration of carbon dioxide inside the room were measured. The analysis showed that despite the lack of a heater in the device, the air temperature in the workplace and in the central point of the room was in the range of 20–22 °C. The air humidity was in the range of 27–43%.

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Most primary school buildings in Poland rely on natural ventilation. This fact is attributed to the age of these buildings constructed more than dozen or even several tens of years ago. Few of them were fitted with a mechanical ventilation system allowing for the adjustment of microclimate parameters. The national requirements for gravity ventilation provide general guidelines, specifying strict description only for the airtightness of windows and doors and the minimum airflow to be supplied to the rooms. The minimum airflow supplied is independent of the number of occupants and purpose of the room. Low indoor air quality (IAQ) can impact occupants’ health and lead to poor productivity or low academic performance. Therefore the provision of good IAQ in classrooms and laboratories is very important. This paper presents the results of the investigation devoted to the quality of indoor air in classrooms of selected Polish primary school. Six primary school in a town with a population of 200 000 inhabitants were involved in the investigations. The participating school buildings were built between 1976 and 1994 and had gravity ventilation systems. The variability of basic IAQ parameters, i.e., temperature, relative humidity and carbon dioxide level, was analysed and the assessment of the classrooms in terms of microbiological purity was performed. The outcomes confirmed the low quality of the indoor air in these buildings. The maximum value of CO2 concentration amounted to more than 4000 ppm. Certain modifications aimed at improving IAQ were proposed during the investigations. Two solutions were implemented. The results of this study indicate that the proposed solution offers the potential to improve IAQ within classrooms.

The article presents the impact of external conditions on the parameters of the air inside the flats and hybrid ventilation. In the vast majority of existing multifamily buildings, as well as in many newly built ones, the way of air exchange is natural ventilation. The air exchange in this system is the result of the temperature difference in the outside of the building and in the ventilation duct as well as the pressure difference caused by the wind. The way to strengthen the exchange of indoor air is to use the hybrid ventilation by using a fan to assist natural air flow in the ''no wind'' periods. When designing the natural ventilation installation, the extreme conditions outside the building are assumed, not including air parameters changing. This article attempts to identify the conditions of atmospheric air which cause the disturbances of exchange indoor air and it attempts to decide when a fan should work to assist natural ventilation.

Indoor air quality attracts great interest. Many dwellings are ventilated naturally. The article presents the gravity system conversion into individual air supply system, which can be equipped with air fan. This solution's impact on the interior microclimate was analyzed. The proposed solution uses the lower natural ventilation ducts sections, which are not normally used as air supply channels to bring air to the housing. Exhaust grilles were located in the adjacent rooms. Individual air supply system with switched off fan improves indoor air quality insufficiently; however, switching on the device causes a very significant change. A large carbon dioxide concentration reduction (which was used as an air quality indicator) has been confirmed by rigorous statistical analysis, the results of which were presented in the article.