Estimating monthly latent cooling demands

Methods of estimating monthly cooling loads in buildings are usually confined to sensible demands only, with latent loads either ignored or added as an arbitrary proportion of sensible cooling demands. This note describes an extension of an existing monthly method for estimating sensible cooling demands that takes account of latent cooling. It reflects the effects of climate, ventilation rate and indoor moisture gains and also of some less widely appreciated impacts of system design. These are illustrated by an example typifying UK office conditions. In order to be workable, the methodology contains a number of simplifications, where precise estimates are needed, and more sophisticated methods should be used.

Practical application: Estimates of annual cooling energy demand made with existing monthly procedures do not account for the size of latent cooling loads or the ways these vary between different forms of air conditioning systems. This note shows how this can be done though, where this is a critical design parameter more complex methods are recommended.