Abstract: The present invention relates to a system and a method for measuring humidity in a ventilated space (3) comprising humidity sensing means (10), a heating device (201), and a control system (301) having access to pre-stored values on saturation vapor content of air at different temperatures. The relative humidity, Hrel(T1), at a first temperature, T1, is measured, with the heating device inactivate. For TI a pre-stored saturation vapor content value, Vsat(T1), is found. A first absolute humidity value, Vc(T1), is calculated by multiplying the first saturation vapor content value by the first relative humidity value. A second relative humidity, Hrel(T2), at T2 is measured, with the heating device on, a second vapor content value, Hsat(T2), at T2 is found and a nominal relative humidity value, RHnom, is calculated by dividing the first absolute humidity value, Vc(T1), by the second saturation vapor content value, Vsat(T2).

Abstract: The present invention relates to a ventilation arrangement for ventilation of a space (3) in a building, comprising a first chamber (A), a first connection (53) connecting the first chamber to an air supply duct (1003) to allow forced supply of exterior air, a second connection (4) connection the first chamber (A3) and the space (3), and a control system (303). The first chamber (A3) has a third connection (63) allowing supply of recirculated air into the space (3), at least partly via the first chamber (A3), a mechanical ventilation damper (123) to prevent air flowing out from the chamber through the air supply duct (1003), a humidity sensing device (103), a first driven fan (83) arranged at the first connection (53) for supply of exterior air, a second driven fan (93) at the third connection (63) for forced recirculation of air. The control system (303) alternatingly drives the first and the second fan. The humidity sensor measures the relative humidity of exterior air and of recirculated air.

Abstract: The present invention relates to a system and a method for measuring humidity in a ventilated space (3) comprising humidity sensing means (10), a heating device (201), and a control system (301) having access to pre-stored values on saturation vapour content of air at different temperatures. The relative humidity, Hrel(T1), at a first temperature, T1, is measured, with the heating device inactivate. For TI a pre-stored saturation vapour content value, Vsat(T1), is found. A first absolute humidity value, Vc(T1), is calculated by multiplying the first saturation vapour content value by the first relative humidity value. A second relative humidity, Hrel(T2), at T2 is measured, with the heating device on, a second vapour content value, Hsat(T2), at T2 is found and a nominal relative humidity value, RIInom, is calculated by dividing the first absolute humidity value, Vc(T1), by the second saturation vapour content value, Vsat(T2).

Abstract: The invention relates to a method and a device in order to protect spaces against moisture damage, based on adaptively controlled ventilation so that the ventilation is maximized when the vapour content of the supply air is lower than in the space. Simultaneously, surrounding building spaces are protected from harmful consequences of earlier moisture damage or of ground emissions of, e.g., radon gas or methane gas, by the fact that ventilation is arranged so that a minimum pressure drop always is present between the surrounding spaces and the protected space, which prevents gases and aerosols from being spread to surrounding occupation spaces.