Dynamic growth of photovoltaic capacity in Poland encourages many entities to invest in photovoltaic systems. However, in the case of buildings with low roof-bearing capacity it can be problematic or even impossible to mount conventional PV modules due to their relatively high weight. Hence, the use of lightweight PV modules is a potential solution. In this paper four different prototype silicon lightweight modules of novel structure manufactured by the Xdisc S.A have been investigated in terms of their electrical and thermal features. The measurements showed that all prototypes have efficiency exceeding 19.5% and power in range of 214 to 242 Wp at standard test conditions. Their area density is about 3.5 kg/m² which is typical for lightweight modules. In turn, the Power-to-Weight Ratio exceeds 40 W/kg threshold and in one case reaches almost 58 W/kg. Thanks to the measurements, the prototypes could be modelled in PVsyst (PVsyst SA, Satigny, Switzerland). The performed simulations of an example PV system revealed that installations based on prototypes have comparable performance to a conventional installation. Nevertheless, at current prices they are less profitable than the standard system and it shows the need for future cost reductions in the manufacturing process. The proposed materials selection may be the starting point for search of inexpensive substitutes of these materials which still conserve modules high performance. A system based on the prototypes can still prove advantageous when simplicity and promptness outweigh higher initial costs.

Fine particulates observed indoors exhibit high variability, influenced by both indoor emission sources and the infiltration of outdoor particles through open spaces and the incomplete building insulation. This study examines the relationship between indoor and outdoor PM_2.5 levels in Legionowo, Poland, using data from low-cost air quality sensors operated by citizens. The indoor PM_2.5 was lower than outdoor levels (median PM_2.5: 1.9–17.3 μg m^–3 indoors and 6.7–27.9 μg m^–3 outdoors), with occasional peaks attributed to potential indoor emission sources. Statistical analysis identified emission events—particularly during cooking and household-heating periods—occurring more frequently from October to April. During this period, nearly 17% of indoor PM_2.5 measurements were attributed to indoor emission sources after 18:00 LT, representing a 7% increase compared to the May–September period. In the absence of indoor sources, outdoor particles accounted for 29% to 75% of indoor concentrations, highlighting the significance of infiltration. This research emphasizes how citizen-generated data using low-cost sensors, after post-processing, can provide decision-ready information as for example outdoor particles’ infiltration factors for each building. The knowledge of the infiltration factor enables the determination of the contribution of indoor and outdoor sources to each resident’s exposure to airborne PM. This information can help decision-makers in devising interventions such as prioritizing indoor ventilation, reducing indoor activities resulting in increased exposure, and addressing outdoor pollution sources.