Gravity ventilation works well in old detached houses if the shower and sauna are built outside the house in their own separate building, and if modern radiator and floor heating are turned down and wood is carried to the fireplace daily. The problem is that very few comfort-seeking residents are willing to do this.

What happened when indoor showers arrived

It's probably not wrong to say that a house with indoor shower facilities and gravity ventilation is a risky construction. The moisture load is many times greater compared to older homes where there were no showers. Warm air holds moisture, and the moisture travels with the air, usually all the way to the attic. In attics of houses with gravity ventilation, you can often notice darkened roof trusses and even condensation on the underside of the roof.

The consequences of insufficient ventilation in damp spaces, such as condensation problems in the attic, can always be remedied afterwards. For example, by increasing roof ventilation or adding an underlayment. However, this does not resolve moisture problems in the insulation or wool in the attic, nor their cause, which is the shower.

Increasing attic ventilation to eliminate attic condensation problems

It is often wise to add larger ventilation openings to the attic, but this unnecessarily brings cool air masses into the attic, causing the attic to cool down and resulting in heating costs for the building owner. It is therefore always wiser to improve the ventilation of damp spaces so that heat can also be recovered from the well-heated indoor air, so that ventilation devices do not cause excessive electricity bills in the future.