The Cost of Triple Glazing

It costs more to manufacture triple glazed sealed units compared to double glazed ones since there is an additional chamber that needs to be filled with argon gas, an extra spacer bar, an additional pane of toughened glass and increased transport expenses due to size and weight. Compared to aluminium double glazed windows, this works out to a basic additional square metre cost of about £100. That means an average 1220 mm (4 ft) square window contains about 1 sq-m glass. That would add about £100 to the cost of an average-sized double glazed window.

How Much Does a Triple Glazed Window Cost?

Although we have an extensive window range and a number of different material choices and systems, we will focus on our white standard UPVC window system that has a few openings in the double glazing. For this system, the installed value, which includes VAT, would be about £465 (correct as of July 2019) and the equivalent triple glazed system would be about £565, or 22% higher.

Triple Glazing and Heat-loss via Windows

Houses in the UK tend to lose as much as 20% of heat via the windows. Therefore, if you are planning to change your windows, fitting them with the best-insulated product is a good idea. You would need to weigh the savings on your heating bills with the additional expense of triple glazing since the payback time definitely will not be overnight. One of our customers said that they want to live as comfortably as possible, and that is why they feel that the right product for them is triple glazing. Of course, the ultimate decision is yours to make.

Triple Glazing Benefits

Installing triple glazing inside your home does offer some important benefits. The main one is heat insulation. However, it is important to keep in mind that not all triple glazing is the same. Numerous triple-glazed systems are available. However, in order to receive the maximum benefit from them, there needs to be 16 mm gaps in between the panes of glass and they need to be filled with argon or another inert gas. Heat loss via the panes is reduced by argon gas. Reducing the gap will also reduce the thermal performance of your sealed unit unless an expensive gas such as krypton is used. Therefore the optimum size for a triple glazed seal unit is 4 mm glass with 16 mm gaps. In the glazing industry, it is referred to as a 4/16/4/16/4 unit, which is 44 mm in total. If the u-values (or heat loss) of the glass is compared, there is big difference between a 28 mm double glazed unit and 44 mm triple unit. A double glazed unit has a typical centre pane u-value of 1.1, while the triple unit is 0.62, which is a more than 40% improvement. This is great for the environment as it reduced heat-loss into the atmosphere, all window purchase decisions now should be for energy efficient windows.

Energy Rating of Triple Glazing

You can select a window based on the number of panes of glass it has. However, you first should check its WER (Window Energy Rating). That is a more reliable way to predict how thermally efficient a window will be after it has been installed. WER is the standard method used in the UK to calculate the amount of heat that will be lost via a window.

The following is taken into account by WER:

  • Air loss through a window.
  • U-value calculates how thermally efficient a whole window is, using the frame material as well as the glass.
  • The amount of heat from the sun passing through the glass that warms up your house. Triple glazing in most cases does not increase the amount of solar gain compared to double glazing, however, a well-insulated window does retain heat well, but not enough to increase solar gain.

Summary of Triple Glazing Cost

Triple glazing is more expensive than double glazing. According to our calculations discussed above, it is 22% or more. However, those are only KJM’s cost. In general, if we were to compare a ‘national’ glazing company, they are normally a lot cheaper for both triple and double glazed windows. Some of the larger companies might offer a ‘free upgrade’ to get triple glazing. However, what is the starting point on the ‘base’ product? If the starting price is doubled, then a 50% discount will bring it down to a realistic starting point! Keeping that in mind, it is always worth it to seek another quotation.