Thermal stratification in intermittently heated heavyweight buildings (Churches)

Abstract

Vertical temperature gradients have been monitored hourly during the winter heating period in two mediaeval churches with typical usage once or twice per week. Little stratification was found except during periods of solar gain, and temperature inversion often occurred because of heat loss through uninsulated roofs. Correlations between vertical temperature gradient and ambient temperature have shown the effect of roof heat loss, and this has been confirmed by dynamic thermal modelling using measured temperatures. Modelling of buoyancy-driven convection in one church has demonstrated the internal airflow patterns and verified the lack of hot air at roof level. Where roofs are uninsulated and heating systems low-powered, it should not automatically be assumed that air at high level will necessarily be hot, or destratification fans beneficial.