By Wes Ley,
Low-e storm doors can be a simple way to increase the energy efficiency of your entry door. This makes sense because low-e stands for low emissivity, and involves using a thin, invisible coating that minimizes the amount of infrared and ultraviolet light that come through the glass. In the wintertime, low-e lets radiant heat pass through but doesn’t allow it to come back out, which means it can help retain heat within your home. In the summertime, it helps keep some of the heat out. The UV protection also helps prevent fading of items inside your home.
However…Low-E Storm Doors Can Create a Variety of Issues
When you have a low-e storm door on top of an entry door, it allows heat through the glass, but it doesn’t let that heat to go back out. This creates an extreme pocket of heat between the storm door and the entry door, which is known as a heat sink. This trapped hot air can create a variety of issues such as warping the glass trim on the entry door, or even warping and bowing the entire entry door itself. If your low-e storm door is exposed to high heat or direct sunlight, it’s important to vent it to release the trapped hot air.
A Sheet of Ice
If you don’t have proper ventilation of the storm door, this can become especially problematic in the wintertime. During the day, the sun hits the storm door and creates heat. Then, when the sun goes away and you have cold temperatures outside, this can basically freeze the storm door. I’ve seen storm doors where the glass was just a sheet of ice because condensation is created when the cold hits the warmer air trapped inside the storm door and then it freezes.
Using a low-e storm door without adequate ventilation creates a variety of problematic issues, and that’s why we don’t recommend them for certain applications.