Statistical evaluation of PCM plaster lining impact on indoor temperature fluctuation due to variability of outdoor temperature and solar radiation along a whole spring season

In lightweight buildings, internal temperatures are strongly influenced by external factors, such as fluctuating outdoor temperatures, and solar radiation, particularly during spring and autumn when operated without heating or cooling. Previous studies often relied on measurements over arbitrarily chosen short periods with limited consideration for varying external temperatures or solar radiation effects, leading to conclusions of limited reliability. This paper aims to address these gaps by analyzing data over a full season and applying statistical approach to yield more sophisticated findings. The purpose was to demonstrate that PCM microcapsules applied in the plaster lining of a lightweight construction model house has high efficiency to reduce temperature extremes during a spring season. As a key contribution, Poincaré’s method was utilized for the statistical analysis of the data, with results represented in 3D diagrams as a function of instantaneous outdoor temperatures and solar radiation. The average daily amplitude of temperature fluctuation was 6.3 °C in the reference house and only 3.6 °C in the house equipped with PCM plaster. At low temperatures in the morning, the previously stored heat is retained by the PCM, thereby reducing the extent of cooling down inside the house. During the daily periods of high outdoor temperatures and intense solar radiation, PCM plaster reduces strong indoor warming. Thus, by providing more comfortable indoor conditions throughout transitional periods such as spring with minimal or no need for supplemental heating or cooling, the application of PCM plasters results in 42.9 % energy savings in this calculation. •Statistical correlation among temperatures and solar radiation studying model houses.•Applying the Poincaré method is novel way to analyze model houses' thermal behaviour.•Phase change material plasters reduced seasonal indoor temperature fluctuations.•House with plasters was 7.8 °C warmer nights and 2.2 °C cooler days than reference one.•Heat trap effect was lower in house with plaster compared to reference one.