[jeff5may]

Originally Posted by Ross D

The idea of dehumidifying the air before it is circulated through the building is to reduce the moisture content of the air.

You're on the right track here.

If outside air is used as the building cools at night, it will eventually reach the dew point of the air and the building will become damp, condensing on the cooler surfaces and equipment stored in there.

Not if it is being dehumidified on the way in. The wheel or liquid actually absorbs more water vapor when it gets colder.

By recirculating the internal air during the day, dehumidifying it and heating it, the overall moisture content within the building will reduce. Which will reduce any condensation overnight, it should also contribute to overall higher temperatures within the building.

Ross

The incoming dry air stream will tend to evaporate the water out of the room: furniture, walls, plants, people, everything with moisture content. This will tend to cool the objects within the room due to evaporation. The net heating of the condensation is taken away by the dessicant wheel or liquid solution. This assumes a forced-air setup.

With the waterfall or fountain setups, it has been found that run continuously, they can over-dry the air, wreaking all manner of havoc on woodwork and interior furnishings. Misting systems are being used to provide additional evaporative cooling and make-up humidity, especially in solar-powered systems.