Double Vs Triple Glazing – Is It Worth It?
When choosing double or triple-glazing, it is important to consider the differences in energy efficiency and cost effectiveness.It’s important to understand that not all double and triple-glazed windows available on the market are the same, they can perform differently depending on which you choose.
What is double glazing?
Double glazing is made of two panes of glass, separated by a space filled with argon gas. The gas layer in between the glass reduces the heat transfer across the window, leading to a warmer and healthier home.
What is triple glazing?
Triple glazing is made of three panes of glass, separated by two spaces filled with argon gas. The extra layers of glass and argon gas in triple-glazed windows provide greater insulation by reducing the heat transfer more effectively compared to double-glazed windows. Triple glazing can be 40% more energy efficient and cost as little as 5% more than double glazing with Koffman Limited.
What are the differences between double and triple glazing?
Heat retention:
Heat retention or insulation can be measured in either R or U, they are the inverse of each other. The R value measures the thermal resistance through a material, the U value measures thermal conductivity.The U value is used to measure insulated glass units as it takes into account convection and radiation heat losses whereas the R value takes into account the performance value across the whole unit.
R = 1/U
U = 1/R
Heat retention and thermal efficiency in your windows is important since you can lose up to 50% of heat through the windows. Heat can be lost through, radiation through glazing, conduction through the glazing bars, air leakage around the frame, and conduction through the window frame.
Radiation through glazing: The inside pane absorbs heat from the room and transmits it through conduction and convection to the cooler outside pane.
Conduction through the glazing spacer: This is not an issue with Koffman as all double and triple-glazing windows use “warm spacer”. These are plastic rather than standard aluminium spacers.
Conduction and convection can occur through space between the glass. If glass spacers are too small, air can conduct hear from one glass to another. Larger spacers improve energy efficiency of the glass unit. At Koffman we use 25mm in double glazing and 2x18mm in triple glazing.
Air is replaced with argon gas to reduce heat transfer. However, with double and triple-glazed windows that are not manufactured with argon gas, the warm air within the window panes rises and is replaced by cooler air, this sets up a convection current at which heat transfers from the inner pane through to the outer pane.
Frame: Heat can be conducted through the frame, UPVC which is not conductive and highly insulating does not have this problem. Heat conducting through the frame is a concern for aluminium frames as they are highly conductive. This is solved by adding a thermal break, a piece of insulating plastic in the middle of the frame that stops the transfer of heat, leading to a warmer, dryer home.
Double-glazed windows at Koffman achieve an R value of 1.1, triple-glazed windows at Koffman reach an R value of 2. This is an 81% increase in thermal efficiency. Triple glazing has superior insulation, noise reduction, reduces condensation, and saves money on heating and cooling energy requirements.
Installation
Building materials have very little tolerance for moisture, because of this, buildings in New Zealand are typically built with sizable cavities for drainage. This style means that the frame isn’t particularly air-tight, so a lot of heat is lost through the spaces between the wall and window. This is why it is recommended to either choose UPVC or thermally broken aluminium and have them fitted recessed into the wall. A quick test you can perform to determine the quality of insulation is to touch the inside of your windows. If the glass feels cold, it could be a range of things from:
- The window could be installed not recessed into the wall,
- It may not be thermally broken,
- It could be double-glazing which isn’t as insulated as triple glazing,
- It could have poorer quality Low E glass used
Triple glazing, installed correctly and of good quality should feel similar to the inside temperature when touched and should not feel cold, reducing condensation forming on the windows. When installed properly (recessed), it can also reduce dust and pollutants getting through the window cracks.
Noise Reduction
There is a growing need for windows and doors that dampen noise pollution as urban area populations intensify. There are increasing problems due to aeroplanes, trucks, and machinery which can disrupt the quality of life or sleep.
Double-glazing is effective at reducing moderate levels of noise, such as street traffic or neighbourhood activities. Triple glazing is effective in areas with high levels of noise pollution, such as urban environments.
Noise pollution can be reduced by as much as 80% when using triple-glazed windows instead of single or double-pane options as the extra pane of glass and argon gas acts as an additional buffer against noise. As the sound waves attempt to pass through, they encounter resistance and are partially absorbed, reflected or diffused.
Koffman windows are thicker, European quality. Thicker glass vibrates less, leading to less noise transfer. For extra noise insulation, special glass can be used that has a coating to dampen the sound.
Price:
Check the quality of your windows, a larger price does not always mean better quality, not all triple glazed windows in New Zealand will provide an 81% increase in thermal efficiency like Koffman windows do. It’s important to consider who you choose to supply your windows as locally supplied triple-glazing windows can be 50% more expensive than double-glazed windows and they don’t always offer the best Low E option. Koffman triple glazed windows cost around 5% more than double glazed options for your whole house and always use the best Low E option to improve thermal efficiency and the performance of your windows and doors. Always check the details, ensure you are comparing “apples with apples”.
Why aren’t locally sourced windows the cheaper option?
Locally sourced windows are going to typically cost more because they don’t have economies of scale, manufacturing operations are smaller and cost more compared to Europe. This means Koffman is able to source the best quality European windows without the premium price attached to it. In Europe thermally broken triple-glazed windows and uPVC windows are the norm, a premium price is not added on as it is not recognised as a “premium product” like it is viewed in New Zealand. Locally produced windows have importation costs of all materials included in them so importing windows from Europe does not create extra monetary or environmental cost.
There are common misconceptions about triple-glazing
It will be too expensive:
Koffman triple glazing, which is a premium European product and achieves an R value 2.7x the minimum H1 requirement in New Zealand costs around 5% more than double-glazed windows. Koffman is able to offer an affordable option due to the economies of scale of manufacturing in Europe. The technology and materials available also means you are receiving the best products on the market.
The gain from triple glazing isn’t enough to choose it:
Triple-glazed windows can be 40% more energy efficient than double-glazed leading to a warmer home that spends less on energy. For around 5% more than double glazing for the whole house, triple glazing is going to save you in the long run.
Triple-glazing can lead to overheating:
Overheating is a common problem in newly built homes, there is a misconception this is due to triple glazing windows. The overheating can be caused by a few things but triple glazing is not one of them. Newly built homes are constructed quickly with often the cheapest materials that meet the minimum H1 building standard requirements.The overheating can be caused by non-thermally broken aluminium windows, poor low E coatings (or no low E coatings on the windows), poor ventilation and poor planning on how close buildings with intertenancy walls will function in the summer and winter months of New Zealand. Triple glazed windows will reduce the amount of heat entering the home compared to double glazed windows.
Low E or low emissivity glass shields from solar radiation from the sun, this makes it more comfortable to live in during the summer months. Not all Low E glass is the same, Koffman uses Planiclear with Planitherm XN and this is a premium glass because it reduces heat loss by up to 59% compared to standard double glazing. Do this simple test: shine the light through the glass. If it splits into “rainbow” it has a low E coating.
Is triple-glazing easy to break into?
All Koffman windows and doors are fitted from inside the house and fitted with a multipoint locking system, with a value of either RC2 or RC3, keeping your home secure.
RC2: All-round fitted system with octagonal locking bolts, steel keeps on the frame, lockable window handle and anti-drilling protection which ensures resistance to attempted break-ins.
RC3: Equipped with an even higher number of octagonal locking bolts at small distanced between locking points. RC3 can also withstand intensive burglary attempts with tools.
Windows can still become condensed with triple glazing:
Triple glazed windows typically only create condensation if they are not installed recessed into the walls, this creates a gap between the line of thermal barrier, and/ or if the windows are not thermally broken. If the room is not ventilated moisture will build up to high levels and even walls with have condensation on them. So far, we have not seen condensation on any of the Koffman windows (except on the outside).
Double vs triple-glazing, is it worth it?
Yes it is. While double glazing is the standard requirement and achieves the required H1 building code, performs well, and does its job, triple glazing is a far superior product and is worth the extra cost for the extra insulation, warmth, comfort, and reduced condensation it provides. “At Koffman, we think that in the future, aluminium double-glazed windows will be viewed the same as single-glazed windows are now”. Given the significant investment involved and the complexity of window replacement, choosing between double and triple glazing is a decision you want to get right.