Moisture Safety in Cold Attics with Thick Thermal Insulation

Abstract

AbstractDamage caused by moisture and mold in attics has increased in Sweden during recent decades. The main reasons are thicker thermal insulation between the living space and the attic and lack of a warm chimney. Very thick thermal insulation will result in attics that are more sensitive to convection from the living space. With only a thin layer of thermal insulation, the attic will be warmer as a result of convective heat transfer from the living space. With a warmer attic during the winter, a certain amount of vapor can enter into the attic from the occupied area without causing any damage. With very thick thermal insulation, however, vapor cannot be allowed to enter the attic. Without a chimney, the temperature in the attic will decrease (especially in winter), which will result in higher relative humidity and lower ventilation owing to a lack of buoyancy. A warm chimney will also increase the natural ventilation in the occupied area and hence decrease the amount of vapor entering into the attic by ...