This paper is dedicated to research of the impact of the limited heat source capacity on indoor temperature and energy consumption in serial nZEB residential buildings. This is an innovative aspect as it explores the potential design simplification for different locations, allowing for cost optimization and quicker construction timelines. The objective of this paper is to examine the impact of limited heat source capacity by utilizing thermal mass and optimizing the ventilation operation. Numerical results demonstrate that incorporating thermal mass increases heating energy consumption by up to 1%. The study addresses the impact of limited heating capacity on indoor temperatures and the need to manage ventilation’s impact during peak temperatures using simulation software IDA ICE. The study reveals that a limited heating capacity reduces energy consumption up to 2.6%, but may result in lower indoor temperatures. By optimizing ventilation strategies, energy consumption can be reduced from 2.4% to 4.4% compared to the suboptimal solution, and from 2.8% to 6.5% compared to the initial case. Parametric analysis reveals optimal ventilation operation change-over point at an outdoor temperature of −17 °C during winter. The research provides practical recommendations for adjusting heating schedules, selecting appropriate heating capacities and implementing optimal ventilation strategies.

This paper is dedicated to investigating how short-term indoor temperature drift influences occupants’ thermal sensation in residential nZEB buildings and how this affects the applicability of steady-state comfort prediction. Residential buildings frequently operate under transient conditions, where the classical PMV approach may deviate from reported sensation. The objective of this paper is to evaluate the agreement between steady-state PMV and occupants’ thermal sensation votes under winter conditions to test a regression-based correction index A_eff and an adjusted indicator PMV_adj while preserving the PMV concept. The study uses high-resolution measurements of indoor air temperature and mean radiant temperature synchronised with TSV responses, followed by statistical evaluation using error metrics and correlation analysis. The results show that baseline PMV correlates well with TSV but exhibits a consistent magnitude mismatch under transient conditions. The proposed PMV_adj reduces this mismatch, decreasing NRMSE from 17.61% to 14.00% and slightly improving agreement with Pearson r = 82.18%, R² = 67.54%. Regression analysis shows that A_eff is strongly associated with the indoor air temperature drift rate ΔT_in/Δt with R² = 0.6805, but has a weaker relationship with ΔT_MRT/Δt, R² = 0.1851. The research provides a practical basis for improving PMV-based comfort assessment during winter operation in residential nZEB.

This paper investigates summertime indoor overheating in naturally ventilated public buildings located in a cool temperate Baltic climate, where buildings are traditionally designed for heating-dominated conditions. The study is based on long-term field measurements conducted in two naturally ventilated rooms (a school classroom and a physician’s consultation office) and aims to quantify indoor overheating and examine indoor–outdoor thermal relationships. Indoor air temperature was continuously monitored and analysed together with concurrent outdoor air temperature and global solar radiation data. Overheating was assessed using fixed temperature thresholds (26 °C and 28 °C), exceedance hours, degree-hours, diurnal distributions, and indoor–outdoor temperature correlations; adaptive comfort criteria were not applied. The results reveal a pronounced contrast between the two spaces. The classroom experienced frequent and severe overheating and strong coupling to outdoor air temperature (R² = 0.60), whereas the physician’s office exhibited limited exceedance and a more buffered thermal response, with weaker indoor–outdoor coupling (R² = 0.32). These findings indicate substantial room-to-room variability in overheating behaviour, even under the same climatic conditions. While derived from a limited two-room case study, the results suggest that room-level assessment may be valuable for identifying overheating risks in naturally ventilated public buildings in cool-climate regions.