Annex 41 - Whole building heat, air and moisture response

Combined heat, air and moisture (HAM) simulation at the envelope level and building simulation havebeen two separate activities for many decades now. In HAM-models, inside temperature and inside relative humidity are handled as known boundary condition, while all building simulation tools predict inside temperatures and net energy demand without any consideration for relative humidity.Things started to change when airflow modeling became doable. That step not only allowed a betterquantification of ventilation related energy consumption but it also permitted a refinement of the humidity balances in the building. However, at least two linkages between the building and the indoor environment remained poorly explored: (1) the fact that many adventitious air flows enter and leave the building across the envelope causing a complex pattern of indoor air washing, wind washing, air looping, infiltration and exfiltration in it and(2), the fact that moisture buffering in indoor finishes and furniture delays and dampens the inside relative humidity.Both phenomena have an impact on the energy consumed for heating, cooling and air conditioning, on durability and on perceived indoor air quality. Analyzing those linkages which are at the basis of whole building heat, air and moisture transport and studying the impact on energy consumption, durability and perceived indoor air quality are at the core of the annex 41 activity.