The paper presents an idea for the enhancement of a building's thermal insulation component by adding into the structure a thin layer of a phase-change material (PCM). The proposed solution can be dedicated, for example, to an external partition of lightweight construction. The capacity for latent heat storage allowed it to stabilize the temperature inside the insulation layer in a daily cycle and to minimize the temperature difference between the internal and external surfaces. In this paper, different positions of a PCM layer in the thermal insulation of an external wall were analysed. The main goal of this work was to find the best position of the PCM layer, taking into account the indoor temperature and the meteorological conditions. The authors propose two parameters: the amount of stored energy and the dynamism of the charging/discharging processes. Taking into account large temperature fluctuations on the external surface during summer and winter, it was concluded that, for this specific case, the most appropriate solution would be an external position of the PCM with a melting temperature of 20°C.

Detailed analyses of melting processes in phase change material (PCM) glazing units, changes of direct transmittance as well as investigation of refraction index were provided based on laboratory measurements. The main goal of the study was to determine the direct light transmittance versus time under constant solar radiation intensity and stable temperature of the surrounding air. The experiment was conducted on a triple glazed unit with one cavity filled with a paraffin RT21HC as a PCM. The unit was installed in a special holder and exposed to the radiation from an artificial sun. The vertical illuminance was measured by luxmeters and compared with a reference case to determine the direct light transmittance. The transmittance was determined for the whole period of measurements when some specific artefacts were identified and theoretically explained based on values of refractive indexes for paraffins in the solid and liquid state, and for a glass. The melting process of a PCM in a glass unit was identified as a complex one, with interreflections and refraction of light on semi layers characterized by a different physical states (solid, liquid or mushy). These optical phenomena caused nonuniformity in light transmittance, especially when the PCM is in a mushy state. It was revealed that light transmittance versus temperature cannot be treated as a linear function.

Periodical changes of temperature on an external surface of building envelope, e.g., thermal stress or excessive heat gains, is often an undesirable phenomenon. The idea proposed and described in the following paper is to stabilize the external surface temperature in a period of significant heat gains by the originally developed, novel composite modified by phase change material (PCM) and applied as an external, thin finishing plaster layer. The PCM composite is made from porous, granulated perlite soaked with paraffin wax (T_m = 25 °C) and macro-encapsulated by synthetic resin. The effect of temperature attenuation was estimated for two designated periods of time—the heat gains season (HGS) and the heat losses season (HLS). The attenuation coefficient (AC) was proposed as evaluation parameter of isothermal storage of heat gains determining the reduction of temperature fluctuations. The maximum registered temperature of an external surface for a standard insulation layer was around 20 K higher than for the case modified by PCM. The calculated values of AC were relatively constant during HGS and around two times lower for PCM case. The obtained results confirmed that the proposed modification of an external partition by equipped with additional PCM layer can be effectively used to minimize temperature variations and heat flux in the heat gains season.

The main goal of the paper was to numerically analyse the risk of overheating of the Energy Activated External Thermal Insulation Composite System (En-ActivETICS) as an example of Building Integrated Photovoltaics (BIPV). The analyses were conducted with the coupled power flow method (thermal and electrical) for 20 European cities. All locations were analysed considering the local climate in the context of building performance simulation as well as electricity production. The obtained results allowed for the determination of the risk of overheating, which can influence system durability, accelerated thermal ageing, and overall performance. It was revealed that the risk of overheating above 80 °C is possible in almost all locations; however, the intensity considerably differs between southern and northern Europe. The effect of latent heat storage for better thermal stabilization and overall performance was determined numerically for all locations. Finally, the improved solution with a phase change material (PCM) layer beside the PV panel was proposed individually for specific climatic zones, considering the required heat capacity. The maximum panel temperature for improved En-ActivETICS does not exceed 85 °C for any location.

The paper concerns the problem of the modeling of the thermal interaction between the phase change material (PCM) and photovoltaic (PV) panel, in the case of unventilated construction. The study aims to develop the numerical model of such a building element to support its proper future design under variable boundary conditions. The need for such a study comes from the realization of the research project which aims at developing a novel energy-activated thermal insulation composite system. Two different methods of PCM simulation using ESP-r software were compared. The model that was finally proposed was validated against experimental data, which proved its robustness. The MBE for the simulated and measured temperatures on the back of the PV panel did not exceed 2.0 °C and the maximum observed energy production difference was 4 Wh/m².

Modification of a glazing unit by application of PCM layer can lead to the increase of the heat capacity of the component and effective control of solar heat gains in buildings. The purpose of this study was to investigate the effect of the PCM layer on total solar and visual transmittance in solid, mushy (transition) and liquid state of PCM. The experiment was conducted in laboratory scale using triple glazed window unit sample and artificial sun as a source of solar radiation. The transmittance (total and visual) was calculated based on the results from pyranometers and illuminance meters taking into account the intensity of solar radiation at the level of 1000 W/m². Measurements revealed that the component is almost blind in the solid state why in the liquid the transmittance is lower than for empty - traditional triple glazing. The transmitted radiation (total and visible) depends on the location of PCM layer (internal or external window chamber). The registered total solar radiation obtained in solid state was even 0 W/m² (when material was on the inner side), while the maximum values for liquid was 142 W/m² (material is located on the outer side). The light transmittance for more transparent case was around 1.6 klx and ten times higher in liquid than solid state.