Secondary Author(s)

Shirey III, Don B.

Report Number




HVAC; Buildings; Dehumidification; Air Quality; Humidity


In most applications, heating, ventilating, and air conditioning (HVAC) equipment is controlled to maintain an indoor dry-bulb set point temperature. Moisture removal by the HVAC system is considered to be an operational byproduct. During summer months, the operation of the HVAC system is usually sufficient to meet both the sensible and latent cooling loads. However, during other times of the year when sensible loads are reduced, the moisture load can be significantly higher than the available moisture removal capacity of the air conditioning system. This can lead to elevated indoor relative humidity levels and an uncomfortable indoor environment. In many cases, designers, engineers and building occupants combat high indoor relative humidity and associated comfort problems with the use of additional dehumidification equipment for both commercial and residential applications. The use of extra dehumidification equipment can be expensive in terms of first cost and annual operating costs. First costs associated with this type of equipment may include additional electrical circuits, condensate drainage, and additional air distribution systems. The loss of usable floor area, localized noise, and zonal hotspots can also be considered a cost penalty. As an alternative to using separate equipment for meeting both the sensible and latent components of a building's cooling load, off-the shelf products were used to construct a self contained air handler. The air handler is controlled using a low-cost thermostat and humidistat. The dehumidification element of the system is completely independent from the air conditioner and works nearly the same as conventional dehumidification equipment. At times, both the dehumidification equipment and the air conditioner operate in unison when the need arises. The use of dehumidification equipment integrated with a conventional AC system provides a unique solution for moisture control applications. This paper describes the development and testing of this integrated equipment. Although this technology is not new, the integration of a dehumidification system with a standard air conditioner is an innovative strategy that can be used to address moisture control in buildings. This new HVAC configuration would provide a low-cost solution for building owners and a more comfortable indoor environment for building occupants.

Date Published



Original Publication: Raustad, R., and Shirey, D., "Case Study of an Innovative HVAC System with Integral Dehumidifier", Sixteenth Symposium on Improving Building Systems in Hot and Humid Climates, December 15-17, 2008, in Dallas, TX.

Local Subjects

Buildings - Air Quality; Buildings - Dehumidification; Humidity; Buildings - HVAC


FSEC Energy Research Center® Collection



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