Low-e products, such as the Pilkington K Glass™ and Pilkington Optitherm™ ranges are high quality clear float glass with a specially formulated, permanent, transparent Low-e coating applied to one surface during glass manufacture.  
 
The coating allows the sun's energy to enter the building and when incorporated into insulating units, significantly reduces heat loss. It is usually used in insulating glass units with the coated surface facing the cavity.  

Advantages of Low-e glass 

• Improve thermal insulation (lower heat losses), thus saving energy and reducing CO₂ emissions
• Retain warmth in rooms, increasing occupant comfort
• Reduce heating bills
• Reduce condensation, cold spots and downdraughts near windows, increasing useful floor space
• Available as toughened or laminated options for safety and security
• A true low emissivity glass (emissivity less than 0.2)
• Specifically designed to reduce heat loss through a window
• Low emissivity coating allows the free short wave energy from the sun to enter the building, but acts as a barrier to the escape of expensive long wave energy from internal heat sources
• Excellent thermal insulation characteristics, reducing heat loss by 30% over ordinary double glazing
• Windows can become a positive contributor to a building's heating needs by optimising 'free' heat from the sun
• Low E Products can be combined with solar control glasses to offer full energy management solutions