What is the solar heat gain coefficient?

Effectively managing solar heat gain is hugely important.

Be it on a small residential property or large commercial building in London, the impact is the same. If too much heat enters the spaces we live, work and socialise in, it has a negative effect on our mood and productivity levels.

According to a 2003 study, just a 2% increase in temperature has been shown to lead to an 8% decline in productivity.

Furthermore, solar heat gain also has an incredible impact on the energy efficiency of a building. Overheating can become a major issue, leading to an increased use of expensive and carbon-emitting HVAC systems.

Solar shading is a key part of controlling the solar heat gain entering our buildings, and can also have a big influence on a building’s solar heat gain coefficient. But what exactly do we mean by this?

What is the Solar Heat Gain Coefficient?

Though it’s a rather complex topic, we’ll try our best to simplify it. In Layman’s terms, the Solar Heat Gain Coefficient (SHGC) measures the ratio of solar radiation hitting the glazing on a building and the amount which then passes into the building through the glazing and window covering.

However, determining this value is where things start to get tricky. To accurately measure the SHGC, the shading coefficient value is required.

Though widely considered as rather outdated, the shading coefficient compares the heat passing through a glazing system to the level passing through a single pane of glass. The value generated here is then multiplied by 0.87 to provide the solar heat gain coefficient.

Once measured, the SHGC value is presented as a number between 0 and 1, with the lower number usually representing a greater shading coefficient.

However, as with measuring the value, interpreting the outcome also comes with complications. For instance, a lower SHGC is ideal for buildings exposed to direct sunlight in the summer, as this will provide greater control over solar heat gain.

But this could have an adverse effect in winter by not allowing enough heat into the building for warmth. Therefore, when discussing solar heat gain coefficient, a great deal of consideration is required.

In most instances, we would recommend installing an automated control system with a metallised blind fabric. The qualities of the fabric combined with the automated position of the blind creates a scenario in which heat gain is prevented in summer but encouraged in winter, while glare is also excellently controlled.

If you’d like to discuss solar heat gain coefficient in greater detail, please contact us here.