Standards Development

Scope

This international standard specifies a method to measure solar heat gain coefficient for fenestration systems using sunlight (e. g., complete windows, doors, and curtain walls with or without shading devices). It applies to the centre of glazing in fenestration systems which might consist of:

a) various types of glazing (e.g. glass or plastic; single or multiple glazing; with or without low emissivity coatings, and with spaces filled with air or other gases);

b) opaque panels;

c) various types of shading devices (e. g. blind, screen, film or any attachment with shading effects);

d) various types of active solar fenestration systems (e. g. building-integrated PV systems (BIPV) or building-integrated solar thermal collectors (BIST)).

Purpose

Fenestration systems (e.g. complete windows, doors or curtain walls with or without shading devices) are the thermally weakest part of building envelopes. In order to improve these thermal performance, high insulating glazing unit, window with shading device and other advanced fenestrations have been developed and applied in modern buildings. The solar heat gain coefficient, which varies with the direction of the incident solar radiation, is one of the most important thermal performances in case of energy consumption simulation of buildings.

International standards (ISO 19467, 19467-2) have been established for measuring the solar heat gain rate using a solar simulator. However, the equipment for solar simulators is expensive, and this has hindered the widespread adoption of the standard internationally. In addition, although solar simulators simulate direct solar radiation, diffuse solar radiation also accounts for a large percentage of actual solar radiation. For this reason, the solar heat gain rate using a solar simulator does not strictly correspond to the value in a real environment. This international standard specifies a method for measuring solar heat gain coefficients using sunlight as the light source by applying the measurement method of ISO 19467. This makes it possible to evaluate the solar heat gain coefficient of the fenestration system under real-world conditions. On the other hand, since the measurement is done outdoors, the environmental conditions cannot be strictly controlled. This means that the measurement accuracy is inferior to ISO 19467 and 19467-2. For this reason, this standard is proposed as a simple evaluation method.

As this proposal and attached article show, many solar heat gain coefficient values have been accumulated by this method and it has been confirmed that the measured solar heat gain coefficient values of the centre of glazing in fenestration systems without shading devices are almost identical with calculated values based on ISO 15099. This measurement method has capability to be applied on the identifying off-normal solar heat gain coefficient of the centre of glazing in fenestration systems with or without shading devices.