Low-e coatings help windows do their job better.

An efficient window is more than just a piece of glass in a frame – window manufacturers have packed a lot of technology into what looks like a simple product. One of the more impressive technologies is low-e coating – a clear, invisible film that blocks harmful solar rays.  

The “e” in low-e stands for emissivity, a word that describes a material’s ability to give off heat. Low-e windows, therefore, don’t do that. In cold climates, they don’t soak up interior heat and release it to the outside. They reflect it instead, keeping it inside. In hot climates, low-e windows don’t heat up from the outside and transmit that unwanted heat into your home. Low-e coatings keep up to 70% of heat outside in summer, and inside in winter, according to this graphic from the Lawrence Berkeley National Laboratory.  


In both cases, the result is greater comfort and lower utility bills because your home’s cooling and heating systems won’t have to work as hard to maintain interior temperatures.  

There are some extra benefits as well. By blocking 99% of ultraviolet rays – the kind that good sunglasses keep away from eyes – low-e coatings protect the interior of your home. They reduce damage from faded carpets, artwork, wood floors, and furniture by 75%. In addition, the extra layer, thin though it is, adds a smidge of durability to your window.  

Low-e coatings are typically applied to glass during the manufacturing process and have gone from an innovative and uncommon solution decades ago to a core element of today’s modern, efficient window. But if you have older windows, you may be able to apply an aftermarket low-e film to get some protection. These films are sold in versions optimal for hot, cold, or moderate climates and can be applied yourself or using a professional installer to ensure a smooth seal.  

Here’s a quick chart of the main pros and cons to determine if low-e coatings are right for you: