Building Pressure may cause High Humidity issues
There are several things that can contribute to high humidity within commercial buildings. Effectively controlling humidity is an important part of maintaining integrity of a structure and should be a key part of any energy management program.
The HVAC system will typically reduce humidity within a building by cooling the air below dew point which causes the moisture to condense into liquid form. This happens at the cooling coil within an air handler. The air will the pass through a reheat coil which raises it above dew point and also helps to control space temperature.
High humidity can cause damage and mold.
High humidity can make a building feel warmer than it should and also may contribute to mold development. Higher humidity can contribute to other types of damage to the building also.
Buildings that have decorative wood trim or flooring may see swelling. I know of a building that had a wood floor that expanded and contracted so badly that large gaps eventually developed. Humidity was clearly the cause of the issue and the issue could be predicted as the weather changed.
Negative building pressure can contribute to the problem.
One of the causes of this problem that is often overlooked is improper building pressure. Negative pressure within a building will result in humid air being pulled into the building from any available opening.
It is better to have as much air as possible come into the building through the HVAC system where the conditioning of the air will remove a significant amount of humidity from it.
Monitoring and controlling depends on your BAS
One of the major components of controlling humidity is having a building automation system that can monitor and adjust the incoming and exhaust air to properly control building pressure within the structure.
Variable air handler control will change the amount of outside air pulled into the building through the HVAC system. If the amount of outside air drawn into the building through the air handler falls below the amount of exhaust air removed by all exhaust fans in the building, the overall building pressure will become negative.
Most buildings should have a slightly positive pressure to prevent humid air from migrating into the space. Properly monitoring and controlling building pressure can help reduce humidity within the structure.
Different areas of a structure can have different levels of building pressure. Lab areas within science buildings may have negative pressure by design to keep chemical fumes or other hazards contained within those areas.
Those areas should be designed in such a way that allows them to pull air from the other parts of the building without causing them to go negative.