Controlling indoor relative humidity

Hey guys,

I have an issue with the annual simulations when the indoor relative humidity exceeds than 80% in the lack of occupancy or any other source to produce of moisture. I do not want to control HVAC system by turning the humidifier or dehumidifier on. Normally it should be possible to reduce the indoor RH by setting up the mechanical ventilation. When the indoor air can be replaced by fresh air from outdoor. As you can see I defined a schedule for both mechanical and natural ventilation which follows the occupancy. but it seems that during the cold months sometimes when the occupancy is zero, the indoor RH goes high and reaches 80% or more. I changed a lot of parameters, even setting both natural/mechanical vent on 24/7 days on but nothing was changed. It seems that no fresh air from outside can be entered by ventilation.

Hi,
Are you using Detailled HVAC or Simple HVAC?

If you are in Simple, your settings seem right but the schedule or may be inheritance between building level and zone level can interfere.

Regards,

Thanks for the reply. I checked all the parameters and set all in building level to see wether it is effective or not. Nothing happened and as you can see RH during the occupant hours goes up to 80-90% which is unreallistic during November. Normally it would be possible to reduce the humidity by bringing fresh air using natural or mechanical ventilation.

Thanks for the reply. I checked all the parameters and set all in building level to see wether it is effective or not. Nothing happened and as you can see RH during the occupant hours goes up to 80-90% which is unreallistic during November. Normally it would be possible to reduce the humidity by bringing fresh air using natural or mechanical ventilation.

The %HR is waving on the last days and air temperature is quite constant. This means some water vapour is injected (people, outside air, other ?) and removed (probably mechanical ventilation).

We can't juge of the vapour balance with this graph alone but you can check the inputs and their impacts to better understand the curve above.

Regards,