What is a G-Value?

by | Sep 29, 2023 | Last Articles | 0 comments

Solar Gain Coefficient (g-value)

In the context of windows and glazing, the g-value, also known as the solar heat gain coefficient (SHGC), represents the fraction of solar radiation (both directly transmitted and absorbed and then reradiated) that enters a building through a window or glazed surface. It is expressed as a number between 0 and 1, with higher values indicating a greater ability to transmit solar heat into a building.

The Importance in SAP

The more solar energy that enters a building, the less space heating that is required in the winter. But, in the summer this can lead to overheating.

Like everything in energy modelling, there needs to be a balance. That is why overheating needs to be assessed at planning stage and a full design is carried out to avoid issues further down the building process.

Other Considerations

  • Acoustic Attenuation
  • U-values
  • Off-set/ Thermal bridging
  • Passive Ventilation
  • Purge Ventilation
  • Means of Escape