Today in addition to the design of structures, layout solutions, and the design of suitable materials, the modern construction industry also addresses meeting the requirements for the energy performance of a building, with which the topic of the quality of the indoor environment is fully intertwined. Comfort in the use of buildings, and especially the provision of thermal comfort, is a fundamental aspect in the design of technical equipment systems, where a properly selected system regulating the indoor environment can affect b oth t he e nergy p erformance o f t he building and the quality of the indoor environment. One of the important factors is the air quality, where the main factor that af-fects the indoor environment is the concentration of CO2, whose value affects the biological functions of the human organism. The subject of this research is an evaluation of the indoor air quality in a kindergarten because children are more sensitive to environmental influences.

Lightweight timber-based structures are an increasingly common part of envelopes of new buildings due to increasing requirements for their energy performance. In addition, due to the fact that wood is a sustainable material, it can be assumed that the share of these structures in civil engineering will continue to increase. The subject of this article is the thermal analysis of timber-based lightweight structures under winter conditions to expand information about thermal processes in these structures. This article deals with the lightweight timber-based external wall structures with a ventilated facade and a double-skin roof structure. Experimental temperature measurements inside the structures and ventilated air gaps are used to perform the thermal analysis. By comparing experimental and theoretical data obtained by performing numerical simulation, it was shown that for achieving an ideal match of numerical simulations and measured physical properties it is necessary to take into account not only external temperatures affecting these structures, but also other factors such as solar radiation and heat emission into the cold night sky. In the case of the external walls with ventilated facade, the benefit of a ventilated air gap has been demonstrated in relation to smaller temperature fluctuations that affect the structures.

The design of a suitable ventilation method for buildings aims primarily to improve the quality of the indoor environment of buildings and thus to influence individual parameters of the indoor environment such asCO2concentration, air purity, the required amount of fresh air according to the proposed operation of the building, temperature and humidity. Proper design and installation of a forced ventilation system with heat recovery can significantly reduce the energy required for heating or cooling. The paper focuses on the ventilation of a building in summer and its effect on the indoor air temperature, which is an important parameter in the assessment of thermal stability. The building under consideration is a building designed using lightweight building structures that meet the standard requirements for the thermal technical properties of a building in the passive standard. The computer program DesignBuilder will be used for the calculation, which allows the assessment of alternative ventilation solutions under identical climatic conditions by means of dynamic simulation on a 3D model of the building. A critical room where the highest daily temperatures are reached will be used for the evaluation.