Off-normal solar optical property measurements using an integrating sphere

Shading devices attached to windows can be used to control solar gain and hence reduce building peak load and annual energy consumption. The performance of a shading device in this regard is strongly dependent on its solar optical properties. The current study discusses a unique measurement technique that was used to obtain off-normal solar optical properties of flat shading materials. The off-normal properties were needed in order to develop solar optical property models both for shading materials and shading devices. These models provide useful input to building peak load calculation and annual energy simulation tools. Special sample holders were designed and fabricated to facilitate measurements using a commercial spectrophotometer with integrating sphere attachment. A combination of theory and companion tests were used to confirm the validity of the approach.

► A technique was developed to measure the off-normal optical properties of materials.
► It can be done using an integrating sphere with simple to build tube inserts.
► Beam and diffuse components can be measured, but no directional characteristics.
► The error introduced has been quantified.