Thin layers of special materials can be added to glass to make it reflect heat, creating heat mirrors. These coatings improve the glass's ability to keep heat inside, reducing energy loss. Scientists study how different materials affect the glass's ability to reflect infrared light. By measuring how much light is reflected, transmitted, and absorbed, they can create coatings that let in lots of light but keep out heat. The researchers tested different glass samples to see how well they reflected solar and infrared light. They found that by changing the materials in the coatings, they could make glass that lets in light but keeps out heat very effectively.