Buying Windows in a Hot Climate

Written by Matt Mossman, Efficient Windows Collaborative
March 29, 2023

When buying windows in a hot climate, one crucial window-performance rating will help you keep cool inside during hot months.

With winter on its way out, it is prime time for home upgrade projects.  If you are considering replacing your windows and you live in a warm or mixed climate, there’s one key bit of information you need, and you can find it on any window you plan to buy. It’s a rating called Solar Heat Gain Coefficient (SHGC), and it is one of three primary energy-efficiency measures displayed on the label affixed to any window rated by the National Fenestration Rating Council (NFRC), our parent organization.  

Replacing windows is not something that one decides to do on a whim, but if you think it might be time to buy, those labels are your new best friend. NFRC is the primary source for independent, objective window ratings, and these are used to determine what windows qualify for the U.S. Environmental Protection Agency’s ENERGY STAR certification program. One of the benefits of efficient windows is that they help to keep unwanted heat from infiltrating your home, making it more comfortable and lowering your monthly utility bill in the process — because your air conditioner will run less frequently.  

The SHGC rating tells you exactly what to expect from any given window in a number between 0 and 1.  A lower number means more heat blocked.  

According to the U.S. Environmental Protection Agency, people in the Southern climate zone who replace double-pane windows with ENERGY STAR-certified versions save an average of 17% on their average annual heating and cooling costs. If you use them to replace single-pane windows, that savings jump to 31%.

Where you are located will determine what SHGC rating is ideal. Use the map on the left to figure out your zone. At a minimum, you should ensure your windows are ENERGY STAR certified. Windows can’t be ENERGY STAR certified unless the SHGC is at or lower than:  

Northern climate zone – .32 
North Central – .40 
South Central- .25
Southern – .25 

Now, it’s true that windows are not a quick fix for your AC bills – they’re something you replace once every 15 years or so, not when the temperature rises. But if replacing your windows is on your home improvement to-do list, choosing efficient windows has the potential to lower your AC bills and keep you more comfortable during the hot months. And the tax incentives available through the Inflation Reduction Act will make them cheaper. To help you get started, check out the Choosing Windows page on our site, and use the Window Selection Tool to find windows that meet your criteria.

Original article found at Efficient Windows Collaborative