Newer building code requirements based on ASHRAE Standard 62 require much more ventilation air than in the past. This brief article summarizes field research which compared a year and a half of monitoring of two identical stores in Nebraska; one which used a desiccant-based system to dry the increased ventilation air, and another store which used conventional rooftop units to treat the lower amount of ventilation air allowed by earlier codes. The study documented the cost of operation, and the humidity levels achieved in both stores.

Modern ventilation rates for schools greatly improve indoor air quality, as documented by field measurements taken in 10 new schools in Georgia during a multi-year research project sponsored by the U.S. Department of Energy. Five of the schools were equipped with desiccant-based dehumidification of ventilation air, and the other five used only conventional cooling units with no dedicated dehumidification. This article provides a brief summary of that extensive project. Among other interesting results, the measured data shows that, when humidity is really held to 50% rh and when teachers had control of room thermostats, they kept the temperature about 2° F higher than in the schools without dedicated humidity control. This preference has the potential for significant energy savings for dehumidified schools located in humid climates.

While desiccant systems generally provide superb dehumidification, they are not always less expensive to operate than conventional systems. Results depend on system configuration and on application engineering. Data from this field monitoring project demonstrate the importance of commissioning to ensure optimal system performance, and the importance of minimizing pressure drop to keep operating costs low.

Portable desiccant dehumidifiers are commonly used to dry out buildings after floods, fires and disasters. A somewhat less well known application is drying out materials that have absorbed excessive moisture during construction. This practice allows building projects to stay on schedule while limiting the potential for mold problems. This article describes the techniques and equipment used for that purpose.

Over the last 50 years, the largest single application for desiccant dehumidifiers has been for humidity control in un-heated warehouses, laid-up machinery and stored military equipment. This article describes the humidity-related corrosion rates for different metals, and also describes two applications of desiccant equipment in metal storage warehouses, one small and one large.

Photoresist materials used in integrated circuit manufacturing sometimes demand lower than usual humidity levels to avoid swelling or condensation while drying. This article describes an emergency retrofit of a wafer fab operation in Arizona, using a desiccant dehumidifier to provide a stable humidity level at 35% rh. The information includes measured values before and after the desiccant installation.

This practical reference book was developed under ASHRAE research project 1047, and intended for "the designer who has to get it done by Friday." It covers the full range of dehumidification issues in commercial buildings and describes typical equipment configurations for both desiccant and cooling-based dehumidifiers. It also contains separate chapters dealing with issues specific to different building types, including schools, offices, hotels, museums and hospitals and eight others.