Control of Winter Surface Condensation in a Tissue Paper Production Hall: A Measurement-Calibrated, TMY-Based Comparative Assessment

Winter surface condensation on the walls and false ceiling of paper production halls degrades the building fabric, promotes mould growth and disturbs the process environment, yet the choice between the available remedies—envelope insulation, ventilation intensification and mechanical dehumidification—is rarely supported by a common quantitative basis. This paper reports a measurement-calibrated assessment of the three solutions for a tissue mill in Petrești, Romania, housing two tissue machines in a 34 800 m3 hall enclosed by an uninsulated 200 mm reinforced-concrete wall (U = 3.89 W m−2 K−1). Two measurement campaigns established an exhaust airflow of 85500 m3 h−1 (2.46 h−1) and a process-driven humidity-ratio increment across the hall of Δx = 8.0 g kg−1 with one machine running and 12.2 g kg−1 with both, corresponding to a moisture uptake of 18.4 and 27.2 t d−1 respectively—3.7 to 3.9 times the value declared in the process water balance, which indicates substantial hood spillage. A one-dimensional surface-temperature model coupled to a psychrometric zone model was driven by an 8760 h typical meteorological year, yielding 5053 cold-season hours (outdoor temperature below 12 °C). On the existing wall, the internal surface resistance carries 50.6% of the total thermal resistance, so the surface temperature closely tracks the outdoor temperature and condensation occurs in 91–100% of cold-season hours for any indoor temperature between 20 and 35 °C; eliminating it by heating alone would require 45–52 °C indoors. Adding 50 mm of external EPS removes condensation in all 5053 h once the hall is held at 27 °C; at the recommended minimum design temperature of 28 °C, which keeps a margin of at least 1.5 K over the season, it saves about 690 MWh per season and the cost is recovered in 1.9–3.1 years, whereas ventilation intensification (2.3× the present airflow) and hybrid coil-plus-desiccant dehumidification achieve the same technical result at ten-year costs of 3.6–4.1 M€. A sensitivity analysis confirms this ranking. Once the wall is insulated, the dehumidification duty of the plane wall falls to zero and the airflow required to prevent condensation drops below the installed capacity, so the existing ventilation need not be increased: insulation does not compete with the alternatives, it makes them unnecessary.