Double glazing has been a mainstay in new build homes for the past 25-30 years. But how is it made, and why is it so different to normal glass windows?

With double glazing there are two sheets of glass. Despite these sheets of glass being of very high quality, they’re still not great at conserving heat. What conserves the heat is usually what's between the glass. Or more appropriately, what's not between it.

Prior to sealing, oxygen (which is pretty good at distributing heat by convection) is sucked out and replaced with either an inert gas (usually Argon, which has 67 percent the thermal conductivity of air), or simply not replaced and left in a vacuum. These insulate the glass.

Double glazing (also known as insulated windows) has three main benefits:

Prevents heat loss or gain

Double glazing reduces heat loss or gain through the window because the barrier insulates the room from differing air temperatures at either side of the glazing unit.

Although double glazing insulates against differing air temperatures, it does not insulate against radiant heat. This makes a double glazed unit a good choice for permitting the winter sun to warm the inside of the house.

Keeps noise pollution down

Through the vacuum created between the two sheets of glass, noise pollution is greatly reduced.

Reduces condensation

The third benefit of double glazing is that it helps reduce condensation. Condensation commonly occurs on the inside of single glazed windows due to the warm air inside the house being cooled by the cold outside air. With a double glazed window the insulating barrier prevents the transmission of air temperature and therefore prevents condensation occurring.