ISO 15099:2003 specifies detailed calculation procedures for determining the thermal and optical transmission properties (e.g., thermal transmittance, total solar energy transmittance) of window and door systems based on the most up-to-date algorithms and methods, and the relevant solar and thermal properties of all components.

Products covered by ISO 15099:2003 include windows and doors incorporating:

1. single and multiple glazed fenestration products with or without solar reflective, low-emissivity coatings and suspended plastic films;
2. glazing systems with pane spacing of any width containing gases or mixtures of gases;
3. metallic or non-metallic spacers;
4. frames of any material and design;
5. fenestration products tilted at any angle;
6. shading devices;
7. projecting products.