Impacts of infiltration/exfiltration from wind, stack and buoyancy in A/C design - an EnergyPlus energy simulation case study

Infiltration is rarely considered a critical factor in AC design. Purposed built buildings such as libraries or shopping centres with dynamic occupants may prove otherwise. The main access to Macquarie University Library is through three large doors in the foyer. Infiltration/exfiltration rates through these doors warranted a careful analysis for its HVAC design and sizing. The Airflow Network model in EnergyPlus was utilised to simulate the bulk air flow throughout the whole building driven by the inflow/outflow through these doors with wind-tunnel-tested wind pressure coefficients. Compared with the model without infiltration modelling, the cooling energy in the foyer exceeds it by almost an order of magnitude and significantly more for heating energy due to sensible heat loss in winter. The infiltration/exfiltration energy component alone made up around 13% of the total annual building AC energy.