IMPACT OF HEAT AND MOISTURE TRANSFER THROUGH A MULTILAYER WALL ON THE COMFORT CONDITIONS OF AN OCCUPIED ROOM

Overview & Synopsis

Controlling indoor air quality is today a major concern for three main reasons: occupants' comfort, durability and energy performance. Nowadays, most of the technical solutions rely on active methods for air conditioning. However, materials can moderate the indoor relative humidity (RH) variations thanks to their buffering capacity and therefore they may regulate the RH in a passive way. It could be interesting to exploit this property as it is estimated that approximately one third of the moisture generated in a room can be absorbed by the wall surfaces. The factors influencing moisture balance in buildings are: the moisture interactions between indoor air and materials, the HVAC systems, and the indoor moisture sources. The objective of this work is to account for these factors to propose a realistic estimation of the moisture buffering of materials and its impact on the energy consumption and the occupants' comfort.The first step in achieving this objective is to study the moisture interactions between the environment and the wall materials. Hence, a one-dimensional heat and moisture model at the wall scale is developed in PYTHON by using the capillary pressure as moisture driving potential. Conservation equations for the indoor air will take into account the indoor heat and moisture sources from the occupants' presence which are generated by a multi-agent stochastic simulation tool. Finally, a first estimation of the moisture buffering of materials is proposed. The results highlighted that the use of a hygroscopic material in a wall leads to an important increase in the prediction of the comfort conditions in terms of relative humidity. However, no significant impact on the energy savings was noticed. As hygroscopic materials have an influence on the indoor relative humidity, it could lead to better energy savings if a humidification/dehumidification system is simulated.