Incident Solar Irradiation — Watt/m²

Watt (W/m²) represents the incident solar irradiation — the energy received from the sun on any surface, measured in watts per square meter. DL-Light computes incident solar irradiation on any surface using EPW climate data, building geometry, and material reflectance properties. Virtual sensors can be placed anywhere in or around the model to measure irradiation at any height.

This metric is essential for energy calculations, informing solar panel placement, supporting thermal load studies, and optimizing shading devices. The module is validated against ASHRAE 140-2011.

DL-Light performs precise irradiation calculation using complete geometric data and climatic information. For a specified date range, it calculates the energy received on selected surfaces of the 3D model in terms of W/m², accounting for the location and climatic data. The calculation takes into account:

• Climatic data from EPW weather files
• Glazed and opaque material reflection factors
• Albedo (surface reflectance) values
• Complete geometry of the project and surrounding site
• Surface orientation and tilt angle

Results are computed either for specific periods or for annual calculations, providing immediate understanding of project performance from both energy and comfort perspectives.

DL-Light's Watt module has been validated by comparison with case base 600 of ASHRAE Standard 140-2011, which is the standard for building thermal envelope and whole building performance testing. This validation ensures accurate irradiation calculations for energy simulation and design optimization. The module is particularly useful for evaluating building performance regarding the efficiency of protections like blinds or overhangs, and for identifying surfaces requiring enhanced insulation.

Read the full DL-Light user-guide reference for Incident Solar Irradiation — Watt/m²: Windows guide · macOS guide.