When you have new double glazing installed in your windows or doors, the double glazing acts as insulation. It prevents or slows down the loss of heat through the glass in the windows. Modern double glazing has improved thermal properties over old glazing and the void between the glass panels is filled with gas to improve these qualities. You can purchase glazing that offers different characteristics for different applications – to reduce noise, reduce the level of UV rays, improve thermal qualities and many more properties too.
Where cold air meets a warm surface, condensation will normally occur.
If you have old windows the glass is cold inside, the warm air from inside a house meets the cold surface of the window and condensation occurs inside the property. You will see properties with the moisture running down the inside of the window and onto the window ledge. (does it bring back memories of your childhood or student days!) Without any ventilation damp will occur. This is not a healthy environment for the occupant.
When new double glazing has been installed the pains of glass and void in between act as a thermal barrier. The warmer surface is now on the outside of the property, so when it meets with the cold outside air it condenses on the outside of the glass. Now we are in late September and the temperature outside is dropping lower overnight, we put on our heating and in the morning can see the condensation on the outside of the window.
The condensation on the outside of the glass shows that the double glazing is acting effectively at keeping the warm air in and the cold air out.
The heat is being retained and hopefully you will soon see the difference in your heating bill. Replacing the glass means that whilst you may not be able to see the difference you will clearly feel the difference.