Effects of solar gain on ventilated attic space environment

Poor attic ventilation creates moisture accumulation in the attic materials and ends up with creating durability and mold-related problems. Whereas a properly ventilated attics help in minimizing roof systems' moisture and heat gains. Understanding of airflow and temperature fields in attic space is crucial in designing a high performing roof system. Most computational models which are used to study moisture accumulation represent the air in the attic space with a single node, which in reality is not the case. In this paper, the impacts of solar gain in attic space environment and its effect on performances of two attic ventilation approaches are investigated. Computational fluid dynamics model is used to investigate airflow distribution, temperature difference, and the pressure profile of an attic space with two different methods of ventilation, namely Gable side vent and soffit to ridge vent. The temperature and flow fields in the attic are computed for each attic ventilation scenarios applying different solar gain values which represent three different hours of a sample hot summer day for three different North American cities: Atlanta, GA; Miami, FL; Vancouver, BC. The results show effects of solar gain with varying hours of a day. In conclusion, the results prevail that solar gain has prominent role in attic ventilation effectiveness and can well be captured through detailed flow and thermal analysis.