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In order to make your home as comfortable as possible, new buildings are currently generally insulated. This has advantages, for example heating costs can be saved by insulating the external walls.
But don't tight windows, for example, also pose a risk, as BR24 users argue? This is what users commented on “tree13”that insulating the houses from the outside ensures that “the walls are unable to breathe”. Tightly closing windows would also be bad for air exchange. In the BR24 comment columns, users blame good insulation for the appearance of mold.
Six to twelve liters of water vapor per day in the air
Regardless of whether it is insulated or not, you “basically have to ensure the necessary air exchange in every house,” explains Markus Ruckdeschel from the Upper Franconian Energy Agency in response to a BR24 request. According to him, breathing, sweating, cooking or showering in a three-person household produces around six to twelve liters of water per day, which are released into the air as vapor. This water must also leave the building again, otherwise mold could develop, for example in winter. To prevent this, controlled living space ventilation or regular burst ventilation is necessary.
The basic condition for mold to develop is the fact that water condenses in cold places, Ruckdeschel continues. It's also about avoiding cold spots, such as on walls.
Does insulation reduce or increase the risk of mold?
In general, thermal insulation helps ensure that less heat is lost through the walls, explains Andrea Bitter from the Advisory Center for Energy Efficiency and Sustainability of the Bavarian Chamber of Architects in an interview with BR24. Because the wall surfaces are warmer on the inside, proper insulation reduces the risk of mold.
It should be borne in mind that, for example, new, tightly installed windows or new roof insulation could increase the airtightness in a house. This means that less heat is lost through drafts, but there is also less air exchange and therefore less removal of moisture, Bitter continues. In such cases, such as renovations, it is important to discuss with the experts at the planning or executing company how often the rooms should be ventilated or whether a ventilation system is necessary. However, it is also clear: “If two machines are drying laundry in the living room every day and the sofa is pushed into the corner of the outside wall, even the best planning is of no use,” says Bitter.
Walls cannot “breathe,” as the user calls it, even without insulation: very little water vapor escapes through a brick and plastered wall.
Pay attention to wall structure when renovating
“Incorrect renovation is often to blame for the sudden appearance of mold,” wrote BR24 user “Tom_W” End of November. For example, new, tight windows in an old building pose a risk of mold if the facade is not insulated at the same time.
It is always important to look at the existing wall structure in old buildings, for example, explains Gerd Vaupel from the Building Materials and Components Association for rear-ventilated facades when asked by BR24. For example, you have to look at what materials were used or what connections need to be made to windows and doors. Good insulation alone can increase energy efficiency, but it must be combined with an effective ventilation concept and the right construction to minimize the risk of mold formation, explains Vaupel.
In the comment column, a user who is no longer active summed up that mold is ultimately “a result of incorrect insulation combined with incorrect ventilation”.
The experts also see it that way. For example, master plasterer and building energy consultant Jörg Ottemeier told BR24 that ventilation is the central point when it comes to mold. For example, forced ventilation systems would be installed in new buildings in order to reopen tight building shells. However, it is important that the cold outside air is preheated accordingly using technical know-how.
