Northlights or in-plane rooflights? Thermal energy comparison Available to Purchase

Overheating owing to solar heat gain through in-plane rooflights in industrial shed-type buildings leads to thermal discomfort, increasing demand for artificial cooling and higher energy consumption and carbon dioxide emissions. This paper argues that by using a saw-tooth roof configuration with northlights, overheating in summer is significantly reduced without impairing the quality of daylighting. A comparison of the daylighting and thermal performance of conventional (in-plane) rooflights with a northlight configuration is described, using Lumen Designer for daylighting and TAS (dynamic thermal simulation software) to assess energy needed for heating and cooling. Although daylighting performance of northlights is lower for a given percentage of rooflighting, and heating requirements are 10% higher, the overheating is much reduced. As summer conditions are likely to be increasingly important and heating demand will reduce, it is suggested that modern northlight solutions should be developed.