Which factor can significantly impact the thermal performance of windows?

The presence of low-emissivity (Low-E) coatings is significant when it comes to the thermal performance of windows because these coatings are designed to reflect infrared radiation while allowing visible light to pass through. This characteristic helps reduce heat transfer between the indoors and outdoors, effectively improving energy efficiency. During the summer, Low-E coatings can keep heat out, preventing the interior from overheating, and during the winter, they help retain heat inside by reflecting it back into the room.

By enhancing insulation and reducing reliance on heating and cooling systems, Low-E coatings directly contribute to maintaining comfortable indoor temperatures, thus improving the overall performance and energy efficiency of a building. Other factors like the window frame type, external paint color, and window size do play roles in thermal performance, but none are as explicitly designed for energy efficiency as Low-E coatings.