Fresh-air dehumidification for sealed buildings
2 September 2026Application4 min read
A sealed building with mechanical ventilation brings in outdoor moisture all day. Treating that air before it enters is often cheaper than drying the whole room afterwards.
When a building is closed to save energy, ventilation becomes the main moisture path. Every cubic metre of outdoor air carries water that has to be removed indoors, and in a humid climate that load can exceed the internal process load.
A fresh-air dehumidifier sits on the supply duct and dries the incoming air to a fixed dew point before it reaches the room. The room load then only has to handle what the process and people add.
When this is the right arrangement
The approach suits buildings where the envelope is tight and the internal load is predictable: offices with glazed façades, museums and archives, laboratories, and residential projects with mechanical ventilation.
- The unit is sized on the ventilation rate, not on room volume.
- Supply air is dried to a dew point low enough to absorb internal gains.
- The room itself needs smaller or no additional dehumidification.
What to check before ordering
Confirm the ventilation rate, the design outdoor condition and the duct route to the unit. A fresh-air unit that cannot be reached for filter cleaning will lose capacity quietly over a season.