Insulated glass delivers what every homeowner wants: Lower cooling bills when it’s hot outside and lower heating bills when it’s cold. Insulated glass is the ideal choice for our northern climate. It combines the highest solar heat gain (free energy) with good insulating properties, which is why it produces the best year round energy savings. Not all low-e’s are the same – while most low-e glasses have similar performance from an insulating standpoint, they perform quite differently from a solar heat gain standpoint. Solar heat gain is quite simply the amount of free energy we can get from the sun.