If you’ve been shopping around for new windows, you may have already heard the term “solar heat gain coefficient” or “SHGC” in consultation with a window contractor. Perhaps you’ve read it in brochures or on the energy performance labels affixed to replacement window units. In today’s post, local window and roof replacement company Triangle Home Exteriors explains its significance, and why it bears scrutiny when buying new windows.
Convective Heat and Solar Heat
Windows are one of the avenues where heat makes its way indoors. Other parts of the house, such as the roof and exterior walls, slow down heat transfer with insulating materials. However, the same materials are not effective on windows because they’re mostly made of glass. The prevailing solution is insulated glass, a multi-pane assembly that separates the interior and exterior surfaces of the window glass. The gap between the interior and exterior surfaces can be filled with an inert insulating gas to further slow down heat conduction.
While insulated glass is effective against convective heat — that is, heat that moves through the air — solar heat is a different matter. Being a form of light, solar heat can easily pass through any clear material, including insulated glass. To counter this, replacement window manufacturers apply coatings or film that reduce the amount of light that passes through the windows.
Solar heat gain coefficient quantifies the heat gained through direct sunlight. SHGC ratings range from 0.0 to 1.0, with lower values signifying better heat-blocking capabilities. That is, the lower the SHGC rating, the less cooling your home will need and more comfortable you will be during the summer season.
But why should you even look at SHGC ratings at all? Shouldn’t window manufacturers just make windows with low SHGC ratings at all times? The short answer: it depends. For example, in a home that’s exposed to a cold climate all year round, windows with high SHGC ratings can help reduce their heating costs. There’s also the differences in the way window manufacturers counter solar heat. Some apply a tinted coating or film onto the glass, which can result in darker interiors. Other insulated glass products feature coatings that can selectively block solar heat and UV rays, allowing more natural light indoors.
Learn more about window ratings and how to find the right windows for your home. Give Triangle Home Exteriors a call at (919) 615-1101, or fill out our contact form to schedule a consultation. We serve Durham, NC, and the surrounding communities.