The manufacturing costs of triple glazed sealed windows are quite higher than the double glazed units. For starters, their manufacture involves adding an extra toughened glass, creating a chamber and filling it with argon gas, and an extra spacer bar. The transportation cost is also higher on account of extra weight and size.
On the cost front, the additional cost per square metre is usually around £100. With the average 4ft square window, you can expect to have about 1 square metre additional glass. Therefore, you can expect to pay an extra £100 on the price of the double glazed window of similar size.
What is the Cost of Triple Glazed Windows?
First and foremost, you should note that we have a wide variety of window systems made of different materials. That said, for the purposes of this article, we’ll stick to the white uPVC window system that has two openings in the double glazing. The installation price for the double glazed system inclusive of VAT is around £465 (pricing is correct in July 2019). As such, the equivalent for the triple glazed will cost around £565, or about 22% more.
Heat Loss Through Windows and Triple Glazing
A typical house in the UK will lose as much as 20% of indoor heat through the windows. With this in mind, it makes sense to install the best-insulated window systems available on the market. However, it is not just a matter of purchasing the best windows only. You need to consider the cost implication of purchasing triple glazed windows in relation to the saving such windows will make on the heating bills. Keep in mind the payback time will definitely take some time.
Benefits of Triple Glazed Window Systems
There are plenty of benefits to accrue from having triple glazed window systems in your home, chief among them better insulation. However, not all triple glazing is made the same. The market is awash with triple glazed window systems but you will only extract maximum benefits from your system if it has a 16mm gap filled with argon.
The argon-filled gas reduces heat loss through the panes. When the gap is reduced, the thermal insulation performance of the entire unit is reduced, unless you fill the gaps with expensive gases such as krypton. As such, for the best performance, the triple glazed unit should consist of 4mm window panes with 16mm gaps. In the industry, such a system is denoted a 4/16/4/16/4 unit and it is 44mm in total.
To understand the differences in performance between double and triple glazed units, consider the u-value (the heat losses) of the standard 44mm unit and the double glazed windows that span 28mm. Typically, the centre pane in the 44mm unit has a u-value of 0.62 while the double glazed window has 1.1. This represents an over 40% improvement.
Triple Glazing Energy Rating
When choosing a window to install, do not just consider how many glass panes it has. It is more important to consider the Window Energy Rating (WER) of the prospective window. This will give you a better indication of how well the window will perform. WER is the standard method the UK uses to calculate the amount of heat that will be lost through the window.
The WER rating considers the following:
- The air lost through the window
- The U-Value, which is a calculation of the thermal efficiency of the entire unit, including the glass and frame material
- The amount of solar radiation that passes through the glass, ultimately, warming up your home
Generally speaking, triple glazing window systems to do not enhance solar gain over double glazed. While a triple glazed system is effective at retaining heat, it does not necessarily come with performance improvement in the solar gain.
Triple Glazing Window Systems: Cost Summary
Purchasing triple glazing units will cost you more than buying double glazing, by about 22%, as indicated by the calculation above. You should keep in mind that we have calculated the price estimations above using KJM’s and not the ‘national’ glazing company. We price our double and triple glazed units much cheaper. While some companies will offer a ‘free upgrade’ to triple glazing units, you need to ask yourself what it is the starting point for their base products. If a company double the starting point, offering a 50% discount will reduce the price to a sensible price point. As such, do not just settle for the first quote you are offered; seek another quotation.