Solar heat gain coefficient
Understanding the solar transmittance through translucent and transparent materials such as glass is important for determining the solar heat gain into the space they enclose during sunny conditions. Solar heat gain can be beneficial in the winter, as it reduces the need for heating, but in the summer can cause overheating.
The total solar heat transmittance through transparent and translucent materials is equal to the solar heat that is transmitted through the material directly, plus the solar heat that is absorbed by the material and then re-emitted into the enclosed space. Until recently this was expressed in terms of a shading coefficient which described the amount of solar heat transmitted through a material compared to the amount of solar heat transmitted through a standard sheet of clear float glass 3mm thick.
However, manufacturers are now moving away from shading coefficients. In the USA, they are moving towards the use of solar heat gain coefficients (SHGC) and in Europe, window solar factors or g-values. In essence, these both represent the fraction of incident solar radiation transmitted by a window, expressed as a number between 1 and 0, where 1 indicates the maximum possible solar heat gain, and zero, no solar heat gain. The difference between US and European systems is that they use a different value for air mass.
Actual solar heat gain is dependent on the angle of incidence of solar radiation on the glazing (and so the proportion of diffuse and direct beam solar radiation) as well as the spectral make up of the solar radiation. However, as a simplified method, manufacturers will often only provide a spectrally-averaged solar heat gain coefficient for normally-incident solar radiation. Values for other angles of incidence and for diffuse solar radiation can then be estimated using standard equations or tables for similar windows.
 Related articles in Designing Buildings Wiki
- Code for Sustainable Homes.
- Computational fluid dynamics (CFD).
- Emission rates.
- Energy certificates.
- Environmental legislation.
- Green deal.
- Leadership in Energy and Environmental Design.
- Low-e glass.
- Shading coefficient.
- Solar reflectance index.
- Thermal bridge.
- U value.
- Zero carbon homes.
- Zero carbon non-domestic buildings.
Featured articles and news
Eleven Magazine announce the winner and runners-up in their Moontopia competition.
As January is the time for hitting the gym, Designing Buildings Wiki lists the best gym architecture in the world.
London is at the top of the list of global construction megacities, beating Dubai and Abu Dhabi.
What are the innovative business models of the future, and how to incentivise supply chains to work on a whole life basis?
One of the largest churches in the world, the monumental St. Peter's Basilica.
How thermal comfort is quantified and how it can affect wellbeing.
Snøhetta complete a treehouse cabin that allows guests to lie beneath the Northern Lights.
Christiania is an anarchist 'freetown' in Copenhagen where strange and experimental architecture has flourished.
“UK waste data needs improving” say BRE specialists, in this summary of their report into construction waste.
UandI announce new joint venture with US developer to work on office refurbishment projects.
Why buildings crack, how cracks are categorised and what can be done.
Inaugurated last week, the new Elbphilharmonie concert venue; a soaring new addition to Hamburg's skyline.