Moisture Control and Cooling Energy Use in Residential Buildings

Energy consumed in the Canadian residential sector for space cooling has more than doubled from 1990 to 2002. Cooling requirements, expressed by cooling degree-days have also increased. In parallel, there has also been a noticeable increase in the penetration rate of airconditioning systems: almost 45 percent of households were equipped with some type of air-conditioning system in 2003. A comprehensive ventilation approach requires not only air exchange but also indoor liuinidity control. In hot and mild humid weather, ambient ventilation air presents a much greater latent load on the building than a sensible one. Occupants presently use air-conditioning systems or dehumidifiers in order to reduce the moisture level inside. These systems use large amounts of electricity, are expensive to operate and are useful for only a couple of months a year in some regions, e.g. Ottawa. An energyefficient home may need little sensible cooling during periods of mild temperature, but still require dehumidification typically resulting in higher than desired indoor humidity. This paper presents a field study conducted at the Canadian Centre for Housing Technology (CCHT). The performance of an innovative Energy Recovery Ventilator (ERV) in a singledetached house research facility, compared to the enthalpy performance of a Heat Recovery ventilator (HRV) in an identical house next door, to achieve appropriate indoor humidity levels was assessed. The paper also presents the design of an ongoing project on a Desiccant-based Evaporative Cooling System, coupling active desiccant dehumidification with indirect evaporative cooling, as an alternative to the conventional vapor-compression air-conditioner for residential application.