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Solar Heat Gain Coefficient(SHGC) Explained

What is Solar Heat Gain?

At its most basic, solar heat gain is the heat transferred from the sun’s rays. Solar Heat Gain Coefficient “is the fraction of solar radiation admitted through a window, door, skylight—either transmitted directly and or absorbed/conducted, and subsequently released as heat inside the home. The lower SHGC, the less solar heat it transmits and the greater its shading ability”.

Why choosing the right SHGC is important?

The SHGC you choose impacts the price of your project. If you are in northern hemisphere and you’re selecting a window or façade that is on the south-facing side of the home, in direct sun with no adjacent buildings or shading, you’ll want a product that has a low SHGC and lets in the least amount of solar radiation. Therefore, something low like a 0.25 rating would be best. Alternatively, let’s say the window or façade is in an area with a large overhang and gets no direct sunlight. Selecting glass with a lower solar heat gain could increase your cost while being of no real benefit to your home’s comfort levels as the shading produced by the overhang will make it redundant. The same effect can be accomplished with trees or other obstacles.

Could the money be saved and used for something more useful? Of course it could. Having a façade or window with high SHGC in these scenarios when the seasons are considered can also work very much to your advantage. For example, if you have an overhang that provides shading in the summer but does not block the sun when it’s at a lower angle later in the year, or if you have a lot of trees that will lose their leaves in the fall. You don’t have to worry about excessive heat when it’s warm outside but can take advantage of what sun you do get during the winter.

So what is the optimal SHGC?

In short, it depends. When considering SHGC, you should keep all these factors in mind:

  1. Orientation of the project façade or window (i.e., northern hemisphere or southern, facing south or north, east or west)

  2. Structural overhangs and other obstacles(i.e., shading elements)

  3. Buildings in the immediate vicinity

  4. Climate and the seasons(i.e., Facades in direct sunlight can benefit from a higher SHGC in Canada or must cut their SHGC to lowest possible if in Middle East)

  5. The function of facility (i.e. a school which goes on holiday full summer doesn’t need to bother about very low SHGC and they must enjoy higher SHGC in winter)

Hope you enjoyed this blog, fabrix360 is your Geeky coach for ETFE or glass facades. Do not hesitate to reach us out for any further question.


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