Daylight Transmittance of Real Atria Roofs: Assessing a Novel Photoanalysis Technique

Atria represent a means of achieving good daylight levels in medium to large scale buildings. This can lead to potential energy savings through the reduced need for electric lighting. However, to achieve these savings it is necessary have a good understanding of how daylight is transmitted in to an atrium space. The transmittance of atrium fenestration systems is a poorly understood area of atrium design, with little information available to designers. This study investigated a novel photoanalysis technique that would reveal transmission information without the need for physical illumination measurements. This technique involved capturing a hemispherical image of the roof and analysing it using specialist software to obtain the percentage of visible sky. A real building with a simple A-framed atrium under overcast sky conditions was considered for a case study. Good agreement was found between the photoanalysis technique and atrium illuminance measurements.