This heat loss, or temperature gradient, can be illustrated on a roof assembly diagram. The rate at which the air cools depends on the building material because each material has its own distinctive thermal-resistance property. In doing so, the warm interior air will cool as it passes through a roof assembly. Where there are more heating degree days than cooling degree days, vapor retarders are installed on the interior side of the thermal insulation layer.Ĭalculating the temperature gradient through a roof assembly is not as difficult as it would seem.ĭuring winter, warm interior air wants to move to the exterior of the building. When the outside temperature is warmer than the interior temperature, the roof membrane acts as a vapor retarder. When it is warmer outside (e.g., summer), the warm exterior air moves towards the interior. When it is colder outside than inside (e.g., winter), the warm interior air moves towards the exterior. So what can a designer do to determine this?
To ensure the temperature at the vapor retarder remains higher than the dew-point temperature, a sufficient amount of roof insulation must be installed above the vapor retarder to maintain the vapor retarder at a warm enough temperature. Once a designer determines a vapor retarder is to be used, the objective is to make sure the temperature at the vapor retarder membrane is always warmer than dew-point temperature. A vapor retarder's primary function is to minimize or reduce water vapor diffusion into a low-slope roof assembly and help prevent the formation of condensation.
0 kommentar(er)
