Prediction of hydrothermal performance of building envelope parts coupled with indoor climate

• Published in: ASHRAE transactions Vol. 104; no. 2; pp. 908 - 918
• Main Author: Salonvaara, M H
• Format: Journal Article Conference Proceeding
• Language: English
• Published: 01.01.1998
• Subjects: Carbon dioxide; Diffusion; Hygrometers; Indoor air pollution; Mathematical models; Moisture; Walls (structural partitions)
• ISSN: 0001-2505

During the past few years several different computer models have been developed that can predict the hydrothermal behavior of building walls with different degrees of complexity. A new hygrothermal model has been developed that combines the building envelope parts and the indoor climate. The model is capable of predicting the combined transfer of heat and moisture, including liquid and vapor flow and phase changes of moisture in the porous media and CO sub(2) diffusion and convection. In this study, the effects of water vapor diffusion on the hygrothermal performance of walls and CO sub(2) diffusion on indoor air quality are analyzed. Moisture can have several unwanted effects on the durability of building materials, such as rotting, mold growth, corrosion, and deterioration of masonry. The effect of vapor and CO sub(2) diffusion through building walls on the interior climate and wall moisture contents are presented as functions of ventilation rates for a corner bedroom. The model is verified against small-scale experiments in huts exposed to real environmental conditions. These results are then expanded for a full-scale house using the simulation model. Results clearly show the importance of diffusion processes on the indoor climate at low ventilation rates. At high ventilation rates, the effect becomes insignificant and the indoor climate in the rooms approach each other, as would be expected.