Thermal Properties and Overheating of Ventilated Air Cavities Under Pitched Roof Coverings

Abstract

Ventilated air cavities have been a mandatory part of thermally insulated pitched roofs in the Czech Republic. The purpose of these important elements is, among other things, primarily to prevent condensation of water vapor, which could otherwise endanger the roof structure and thus negatively affect the life of the entire composition. However, their thermal properties are often neglected and their overall design is overwhelmingly approached, due to the very difficult and complex calculation, as an empirical and normative matter without a higher link to the actual properties of the air cavity itself. It is therefore necessary that mentioned properties must be investigated more thoroughly, especially with increasing demands on thermal properties and increasingly extreme temperature fluctuations. This work describes a real full-scale experiment in which the properties of temperature and humidity of ventilated air cavities at the boundary with the external environment were measured. The composition of the experimental roof of the building was measured in all important layers, together with all the external and internal environmental conditions. The output is then a detailed course of behavior, which was analyzed and described.Ventilated air cavities have been a mandatory part of thermally insulated pitched roofs in the Czech Republic. The purpose of these important elements is, among other things, primarily to prevent condensation of water vapor, which could otherwise endanger the roof structure and thus negatively affect the life of the entire composition. However, their thermal properties are often neglected and their overall design is overwhelmingly approached, due to the very difficult and complex calculation, as an empirical and normative matter without a higher link to the actual properties of the air cavity itself. It is therefore necessary that mentioned properties must be investigated more thoroughly, especially with increasing demands on thermal properties and increasingly extreme temperature fluctuations. This work describes a real full-scale experiment in which the properties of temperature and humidity of ventilated air cavities at the boundary with the external environment were measured. The composition of the experimental roof of the building was measured in all important layers, together with all the external and internal environmental conditions. The output is then a detailed course of behavior, which was analyzed and described.