Drying insulation in joists and walls

  • One of the most effective ways of drying insulation in floor joists or a framed construction is to use a low-pressure fan and dehumidifier in combination. This combination makes it possible to route large quantities of dry air through the framed building construction and, for this reason, it is very suitable for drying floor joists, walls, floors and other cavities.

    Picture: Dehumidifier and low-pressure fan drying a framed floor.

    Simple and efficient drying technique for framed constructions

    The technique for drying the insulation in framed floors and stud walls is simple; it aims to provide a large throughput of dry air in the wet construction. The dry air is led directly into the construction from the dehumidifier. If a larger air through flow is required then an additional low-pressure fan of type HP2000XT can be used. . The fan sucks the room air mixed with dry air from the dehumidifier and then forces the air into the construction. The aim is also to obtain a large spread of the dry air in the construction; this involves trying to spread out the inlet points so the dry air will dry the entire framework. To control the direction of the dry air it may be necessary to drill evacuation holes.

    Shorten the drying time with heat

    To shorten the drying time, the temperature of the air used for drying can be increased. The warmer the material to be dried is, the more efficient and quicker the drying process will be, as the vapour pressure in the wet material increases. An increase as small at 10°C can halve the drying time* in some cases.

    *Because the drying rate is directly proportional to the difference in vapour pressure, this means that drying at 30°C 20%rh is theoretically twice as fast compared to 20°C 20%rh.

    Important to consider before drying

    A framed construction should always be vacuumed free of water prior to starting drying; read more about this under suction drying. It is important to bear in mind that the dry, warm air also affects all wooden material in the room where the drying process is being carried out. For this reason, care should be taken to remove or carefully wrap in plastic all furnishings that could be damaged. If possible, plastic enclosure can be used, to limit the area to be dehumidified, and in this way protect surrounding material. A hygrostat can be used to advantage, to control the humidity during the drying process.

Products that can be used for floor joist drying