Technical Glazing Terms

Controlling Solar Gain & Overheating in Highly Glazed Spaces

Solar Gain, also referred to as solar heat gain or passive solar gain, is a term that refers to the increase in temperature in a space or building as a result of solar radiation. There are many ways to control and manage solar gain for effective results. Keep reading to discover the technical solutions on offer at IQ Glass, as well as some external shading solutions to eliminate the risk of overheating in highly glazed spaces.

Solar Gain

The sun's light can be broken down into 3 main parts; ultra-violet rays, infra-red radiation and visible light. It is the ‘infra-red’ element of the sun’s light that causes overheating in highly glazed areas. The sun's radiation travels in short wavelengths through the glazing, the objects inside the living space absorb these short wavelengths of radiation and emit heat at longer infrared wavelengths.

These waves cannot travel through glazing and will be contained within the living space, increasing the internal temperature. This causes the infra-red radiation to be trapped within the space and can cause overheating, referred to as Solar Gain.

South West London glass box extension on top floor

Controlling Solar Gain

Controlling solar gain in a highly glazed environment is possible with the use of Solar Control coatings. These coatings reduce the amount of solar radiation that can enter a space through the glazing and thus reduces the amount of solar gain.

One technical glass solution that IQ offer to combat solar gain is Electro-Chromic Glass, designed to change from clear to dark automatically depending on ambient sunshine, season or atmosphere. This technical glass grants the ability to change the glass G Factor from 0.47 all the way down to a minimum of 0.04, which means that only 4% of the solar infra-red radiation hitting the external face of glass will transmit into the internal spaces.

Using a tinted glass will mean that more of the sun’s rays will be reflected than emitted but this will also alter the natural light transmission. A modern glazing technology using a transparent coating, such as a solar control coating, will reduce the G Factor of the glazing, therefore reducing the amount of infra-red radiation entering a space, with only a small reduction in the visible light transmission.

Managed Solar Gain can actually be used to help supplement your heating system and save money on heating bills by raising temperatures in a room during colder periods. For example, keeping curtains and blinds open on a sunny winter's day will keep a space warm using the solar gain from the sun's radiation, reducing the amount of domestic heating required.

Solar Control Coating applied to glass extension


The G Factor is, also known as the solar factor, is represented as a percentage of the total incident radiation that enters through the glass. This includes the direct radiant influx as well as the infra-red radiation that is absorbed by the glass and then re-emitted internally.

For example, a 53% total radiant influx will be a G Factor of 0.53. The G Factor is measured using a standard testing method EN 410 under the assumption of standard daylight light settings with the internal and external temperatures equal. There are many elements that can alter the G Factor of a glass installation if required.

IQ_Glass_Rusty_House_Solar glass wall

External Shading Solutions

Alternatively, you could shade large elevations of glazing from solar radiation using either internal or external shading solutions. Concealed blind systems would work as an internal solution, blocking the sun when closed whilst maintaining a minimal aesthetic when open. On the external face of a property, large elevations of glass can be shaded by shutter systems or a Louvre roof system.

The Louvre roof system from IQ is designed with flexibility in mind. To reduce solar gain, the aluminium louvres are fully adjustable and can be turned throughout the day to offer the most effective shading angle.

For more information about combatting the effects of solar gain, or to speak to a technical expert about your project, email

Umbris- Kingsland Road 02