Learn the IES recommended uniform method for determining and reporting the photometric characteristics of skylights and
tubular daylighting devices that incorporate a means to diffuse the natural hemispherical daylight as the daylight passes through the daylighting system. LM-81 describes the procedures followed and the precautions observed in obtaining uniform and reproducible measurements of tubular daylighting devices and skylights with glass or plastic glazing; as well as identifying the components and the structure type needed to adequately measure daylighting devices. The procedures, calibration of the equipment, and determination of sun angles and sky conditions are also discussed.
Page count: 17 pages
Publisher: Illuminating Engineering Society (2023)
SKU: ANSI/IES LM-81-20(R2023)
- 1.0 Introduction and Scope
2.0 Test Distance
3.0 Goniophotometer Basic Construction
4.0 Photometer Structure
6.0 Sky Conditions
7.0 Testing Procedures
8.0 Testing Procedure
9.0 Limitations of Skylight Photometry
Illuminating Engineering Society. ANSI/IES LM-81-20(R2023), Approved Method: Photometric Testing of Skylights and Tubular Daylighting Devices Under Hemispheric Sky Conditions. New York: IES; 2023.