Windows, which have a U-value that is governed by an insulating glass unit (IGU) U-value, must be a building’s only enclosure element, which has no design value concept. The declared U-value, which is calculated or measured with 0 °C of external ambient temperature, is used instead of the design value. For most of a building’s elements, its thermal transmittance with a decrease in the external temperature diminishes a little, i.e., improves. However, for modern window IGUs with Low-E coatings, it is the opposite: the thermal transmittance with a lowering external temperature increases. Therefore, for calculating the peak power for the heating of buildings it is necessary to pay attention to this phenomenon and, therefore, it would be wise to introduce the concept of design U-value for windows, recalculation rules, or affix their declared U-values. This is especially the case in modern times with the prevailing architectural tendencies for enlargement of transparent building elements. For IGUs with Low-E coatings and inert gas fillers, the thermal transmittance depends on the temperature difference between warm and cold environments. When the external temperature is −30 °C instead of 0 °C, the thermal transmittance of the IGU can increase by up to 35%. This study presents the thermal properties of windows’ IGUs depending on the changes in outdoor temperatures by using guarded a hot box climate chamber and presents the proposed simplified methodology for determining the thermal properties of windows’ glass units. The accuracy of the composed simplified methods, comparing the calculated thermal transmittances of IGUs with those measured in the “hot box”, were up to 1.25%.

It is important to develop research on sealing materials in order to find effective solutions to ensure the energy efficiency of buildings. The aim of this study is to investigate the peel adhesion of single-sided self-adhesive tapes to different construction surfaces and to determine the change in this characteristic due to climatic effects. Different construction tapes, mostly used externally in buildings, are glued to different substrates. The artificial aging of test samples was carried out, simulating the effects of moisture, heat, and cold; the intensity, duration, and sequence of the cyclic effects were determined, taking into account the statistical climatological data of the middle-latitude climate zone. The peel adhesion of the tapes was determined before and after different numbers of artificial aging cycles. The results show that the peel adhesion range is very wide, from 11 to 61 N/24 mm. In most cases, a lower-rated peeling adhesion was obtained by peeling the tape from plastered cement–sawdust board. The change in peel adhesion depends more on the surface to which the tape is glued than it does on the number of climatic exposure cycles selected for the test.

Ensuring the tightness of buildings using self-adhesive tapes is one of the cost-effective, efficient, and reliable solutions. There is a lack of research, standards, and methodologies for construction adhesive tape, especially for assessing the functional properties of the tape after ageing. The aim of this work is to evaluate the tightness of different building surfaces and adhesive tape systems by conducting artificial ageing. It was found that adhesive tapes with an acrylic adhesive base ensured a fully sealed system. In all cases, tapes applied to surfaces such as plywood, gypsum plasterboard, cement-bonded particle board, plastered cement-bonded particle board, and plastic board provided sufficient sealing. The air permeability of the tapes on the OSB was two to seven times higher than that of the defined sealed system with other surfaces. In most cases, air permeability increased on OSB, gypsum plasterboard, and plastered cement-bonded particle board after ageing. The least problematic surface is the plastic board. In all tested cases, adequate sealing was observed after ageing, with only three of all tested tapes not providing sufficient bonding strength.

Recently, the construction of external ventilated walls has become popular for public and office buildings. These blocks are used without internal rendering because of their good interior surface, stable dimensions and various filling of masonry joints, which provide an attractive architectural appearance. However, problems with the airtightness of such walls often occur. Currently, there are no standard methods to predict the airtightness of such wall. In practice, samples of particular walls are produced, and their air permeability is measured at laboratories. For the broader use of the results of laboratory air permeability measurements, a methodology has been developed to predict the air permeability of block masonry walls using experimentally determined air flow resistances of the individual layers. The masonry from various blocks were used for the research; mineral wool boards of various air permeability were used for thermal insulation and the wind protection layer. After measuring the air resistance of the samples, the air flow resistances of walls of different construction were calculated. This study compared the calculated and measured air permeability values of different wall masonry samples and evaluated the suitability of created calculation method for prediction of the airtightness of insulated block masonry wall.

This research investigates the air permeability and watertightness performance of commercially available windows and doors based on laboratory tests conducted in accordance with the EN 1026 and EN 1027 standards. All tests were carried out under controlled environmental conditions, and the results were validated following relevant ISO procedures to ensure reliability and consistency. The tests are essential for evaluating the air permeability and watertightness of commercial windows and doors to ensure the overall performance, energy efficiency, and durability of the building envelope. The results provided consist of 244 samples (93 doors and 151 windows) tested between 2018 and 2025 in an accredited laboratory complying with EN ISO/IEC 17025. The results show that most doors achieved the highest air permeability class (Class 4) according to EN 12207, with shares ranging from 50% to 80% and exceeding 65% in most years. Window performance was similarly strong, with more than 74% of samples classified as Class 4, indicating consistently high airtightness and compliance with stringent energy efficiency requirements. Watertightness tests revealed that 59% of products were resistant to water penetration, while 41% were permeable. Among watertight products, windows predominated (67%), while doors accounted for a larger share of water-permeable cases. The results support informed decision making in manufacturing, construction practices, and early-stage building design, contributing to improved building durability and energy efficiency.

Polyisocyanurate (PIR) insulation boards are widely used in buildings because of their low thermal conductivity, however their long-term performance is affected by aging. This study investigates the effect of accelerated thermal aging at +70 °C on the thermal conductivity and gas composition of pentane-blown PIR boards. Thermal conductivity was monitored over time, while changes in blowing-agent composition were analyzed using gas chromatography/mass spectrometry (GC/MS). Thermal conductivity increased from 0.0201–0.0211 W/(m·K) to 0.0243–0.0247 W/(m·K), corresponding to an increase of approximately 18–22%, with the most pronounced changes occurring during the first 40–50 days before stabilizing. GC/MS identified isopentane, cyclopentane, and pentane as the main gases in the foam cells, with isopentane as the dominant component. Accelerated aging caused a progressive decrease in blowing-agent concentration, explaining the deterioration in thermal insulation performance. Thermal outgassing proved more reliable than solvent extraction, providing higher sensitivity and reproducibility. Sample location, sample size, and outgassing temperature significantly affected the measured gas quantities, while higher outgassing temperatures improved analytical sensitivity without changing gas composition trends. The results confirm that the aging-induced increase in thermal conductivity is primarily caused by the loss of low-conductivity blowing agents, improving understanding of the long-term performance of PIR insulation materials.