Manufacturers are constantly seeking to improve the energy performance of windows to keep the thermal efficiency of the house intact. There is no point having excellent insulation in the walls, roof and floor of your home, if the windows don’t perform to the same standard. We all know what it’s like sitting next to a drafty window. In any window replacement, a good fit is essential in order to eliminate leaks around the frame. But how much difference does the glass itself make?


Single glazing refers to windows that have only one sheet of glass in the frame. This used to be the only option available and is still common in many older homes. You may choose to keep single paned windows to maintain the architectural integrity and sense of character of your home. Sometimes newer styles can clash with the older aesthetics.

  • Single panes do not provide good insulation and have a high U-Value of around 5. The U-Value measures how well a product keeps heat from escaping; the lower the number the better. Single panes can feel cold to the touch in winter and may even ice up on the inside.

  • Condensation can also be a problem leading to mold and rotting in wooden frames. The inefficiency of the windows results in much higher energy bills, as well as a lack of comfort.

  • Single pane glass is not as resilient as double and can be easily broken, making it more attractive to burglars.  It is however easy to repair a single pane without having to replace the entire window unit.


Double glazing consists of two panes of glass, held apart by a spacer, with a layer of inert gas, such as argon, sealed between them. These sealed units provide far better insulation than single glazing and can reduce heat loss by up to 50%.  The airtight construction reduces the flow of air in and out, using considerably less energy to either heat up or cool down your space. Modern double glazing has a U-Value of about 1.6.

  • Double glazing is more expensive than single glazing and it may take you some time to recoup the cost of the upgrade through reduced energy bills. It does however offer several other advantages.

  • With so many more people working from home, noise during the day can be a huge distraction. Double glazing helps block out the noise of traffic, leaf blowers and those noisy neighbors.

  • Double glazing reduces the sun’s harmful ultraviolet rays that cause skin damage and fading of furniture and carpets.

  • Because double glazing is more difficult to break than single glazing and the shards usually stay in place, it provides increased security. If the window does get broken however, the whole unit has to be replaced.


Triple glazed windows have three panes of glass held apart by two spacers instead of one and sealed with a layer of gas in between. The claim is that the extra pane increases efficiency and reduces noise even further. Many manufacturers are able to achieve U-factors of 1.0 or better.

Norway is a real crusader against energy losses and has the strictest building regulations in Europe. Husbanken, the Norwegian State Housing Bank, is the government’s main implementing agency for housing policy and demands that the average U-Value of windows be as low as 0.8. The only way to achieve this is with triple glazing. If you live in a very cold climate, and the rest of your house is energy efficient, then triple glazing may be worth it. However it will cost you more to install than double glazing for only a slight improvement in energy savings.

  • Triple glazed windows are much heavier than double glazed windows. They need a strong frame material such as fiberglass that is durable and won’t sag or warp.

  • Not everyone agrees on whether an extra pane of glass really improves noise reduction. In some cases it appears that triple glazing can make acoustic problems worse. Double glazing with an acoustic laminate may be more effective.

All in all, the benefits of double glazing over single make it a worthwhile investment if you are considering replacing your windows. If you already have efficient double glazing, an upgrade to triple barely seems worth it.