All materials lose heat, but some more quickly than others. The rate of heat loss depends on the surface emissivity of the material. For example a silver teapot will retain the fluid temperature for longer than a glass teapot because the surface of silver has a much lower 'emissivity'. Emissivity is defined as the rate of emitting (radiating) absorbed energy.

 low-e or sun-e on-line, hard coat, glass reduces heat loss from the building whilst allowing the passage of the sun's heat into the building thus conserving energy during those periods when buildings have to be heated from within.

This clear glass is coated with a metal oxide through pyrolysis. The coating is therefore very resistant to mechanical damage, and this Low-e glass can be cut, tempered or laminated just as normal uncoated glass.