Upgrading your windows is one of the best investments you can make in your home, and this extends far beyond its curb appeal. Whether your home is uncomfortably hot in summer and too cold in winter or your energy bills have been rising due to excessive air conditioning and heating use, upgrading to energy-efficient windows can make a big difference.
Shopping for energy-efficient windows is much easier than it was in the past thanks to ratings that are designed to help consumers make comparisons based on the energy factors that are most important to them. One factor that is important to understand and assess is the solar heat gain coefficient.
What Does Solar Heat Gain Coefficient Measure?
The solar heat gain coefficient, or SHGC, rating indicates the fraction of solar radiation that is transmitted through a window or absorbed by it. This shows homeowners how much solar heat and sunlight will be released into their home through the windows.
Those with a lower SHGC rating have less solar heat gain and a better shading capability, however, this is not always better. The right choice will depend on the climate in which you live.
The National Fenestration Rating Council is a nonprofit organization that carries out independent testing to assign SHGC ratings for windows and skylights. These ratings are listed on the labels of windows as part of the NFRC’s certification program, along with other factors, and are considered by the EPA and U.S. Department of Energy when evaluating a window’s energy efficiency for federal incentive and rebate programs.
Why Is SHGC Important?
To understand solar heat gain coefficient better, it is useful to be familiar with what goes into making a window energy efficient. In general, energy-efficient windows are designed to prevent heat loss and gain.
Windows can gain or lose heat in several ways, including air leakage around the windows, heat transfer through the glass of the windows, solar radiation penetrating through the glass, and thermal radiation.
SHGC gives homeowners information about how specific windows they may be considering will behave in different climates and seasons. Outlined below are the top considerations:
- Protection from UV rays – Prolonged exposure to sunlight can cause a host of unpleasant side effects. Windows that have sub-optimal SHGC ratings put a home’s inhabitants at risk of problems associated with sun damage such as premature skin aging, sunburn and skin cancer. Moreover, furniture and artwork in the home can fade significantly faster when exposed to sunlight on a daily basis.
- Home comfort – Studying the SHGC of a window can help you find the most appropriate type for each room in the home. This can prevent freezing temperatures during winter and overheating in the summer.
- Energy bill reductions – When you use the SHGC rating to choose your windows carefully, you can optimize the overall energy efficiency of your home and reduce your energy consumption, which will help bring down your utility bills.
Choosing the Right Solar Heat Gain Coefficient
SHGC ratings on windows can range from 0 to 1, with 0 indicating that the minimum amount of solar heat possible will be allowed through and 1 meaning that the maximum amount of solar heat can pass through the window. An SHGC rating of 0.40, for example, means that 40% of available solar heat will be able to pass through the window in question.
SHGC ratings are generally assigned to the entire window assembly, including the glazing and window frame, along with any spacers separating the glazing panel. This means that the type of window and its glass will impact the rating.
Some of the most common ratings you will encounter in residential windows are 0.25 and 0.80. The placement of the windows in your home and the climate of your area are the most important considerations in determining whether a higher or lower SCHC rating is more desirable.
For those who live in an area with a warmer climate and depend on air conditioning for much of the year, windows and skylights that have an SHGC ratings below 0.3 are ideal. These windows work best when they are positioned in areas or walls of the home that face south or west and get a significant blast of afternoon sun.
Those living in colder climates will place a greater priority on maintaining a comfortable and warm temperature inside the home without depending too heavily on heating. In this case, windows with a high SCHC rating, such as somewhere in the range of 0.40 to 0.60, can be beneficial. Installing these types of windows in south-facing walls can serve as a good source of passive solar heating.
Discuss Your Window Project with the Northern Virginia Exterior Home Contractors
If you are interested in exploring how energy-efficient windows can improve your home’s comfort and reduce energy bills, reach out to the experienced Northern Virginia window installation and replacement contractors at Adelphia Exteriors to schedule a consultation today.