Climate-specific optimisation of air tightness and heat recovery in nearly zero-energy residential buildings based on typical energy use patterns: A simulation-based approach

Nearly zero-energy buildings (NZEBs) require optimisation of parameters like air tightness and heat recovery to minimise heating, ventilation, and air conditioning (HVAC) energy use. These four climate zones in China are: severe cold (SCZ), cold (CZ), hot summer and cold winter (HSCWZ), and hot summer and warm winter (HSWWZ). Building energy simulations analysed the impact of air tightness and exhaust heat recovery efficiency on the energy use in NZEB archetypes with the identified operation patterns in each zone. Results show SCZ and CZ benefit from improved air tightness up to the Code limit (N<jats:sub/>50 = 0.6), giving 36% and 8% energy savings, respectively, with heat recovery compared with using only infiltration for ventilation. For HSWWZ, reducing airtightness to provide adequate fresh air eliminates the need for heat recovery, yielding the lowest energy consumption. When improving the airtightness, sensible heat recovery suits SCZ/CZ; for HSWWZ, total heat recovery is technically more effective for energy savings; however, due to minimal energy consumption differences, meeting ventilation requirements through infiltration is more economical. Thus, regional optimisation of air tightness, ventilation strategy, and heat recovery selection can facilitate the design of high-performance NZEBs. The established coupled operation patterns also better represent NZEB performance versus standardised assumptions. Implications include revised design code requirements for air tightness according to climate zone, transitioning standards to realistic operating conditions, and selection criteria for heat recovery equipment. The optimisation methodology and results guide the NZEB energy efficiency in China’s various regions.