A TRNSYS-based parametric study of building ventilation systems incorporating Rotary Heat Recovery Wheels

The progressive tightening of building regulations is reducing heating and cooling demands. As a result, ventilation (previously a secondary energy use) has become increasingly relevant. In Spain, current regulations mandate air-to-air heat recovery with minimum effectiveness and maximum pressure drop thresholds, but they are based primarily on airflow and operating hours, overlooking local climatic variability. This study evaluates the energy performance of ventilation systems equipped with Rotary Heat Recovery Wheels (RHRWs) in five representative Spanish climatic zones using the simulation tool TRNSYS . The analysis considers heating, cooling, and evaporative cooling modes following typical tertiary-building operating schedules and various RHRW effectiveness levels. A novel performance metric, E r a t i o (defined as electricity use per cubic meter of fresh air supplied), proved useful for cross-climate comparisons. In heating mode, E r a t i o ranged from 1.5 Wh e /m 3 in colder zones to 1.0 Wh e /m 3 in milder ones. In cooling mode, hotter climates reached 1.0 Wh e /m 3 , while colder zones stayed below 0.5 Wh e /m 3 . Evaporative cooling achieved over 50% energy savings in hot climates, though it required significant water consumption. A key contribution is the development of robust correlations between E r a t i o , standardized climatic indicators — Heating Degree-Days (HDD 18 ° C ), Cooling Degree-Hours (CDH 18 ° C , CDH 27 ° C ) — and heat recovery effectiveness, providing a predictive framework for ventilation system design. • Ventilation energy use in tertiary buildings was assessed across 5 Spanish locations. • The simulation tool TRNSYS was used to estimate the performance of the system. • Rotary heat recovery wheels performance was assessed under heating and cooling modes. • Strong correlations found between ventilation energy use and HDD/CDH climate metrics. • Evaporative cooling saved > 50% energy in hotter climates, with water use trade-off.