Double or triple glazing: which is right for your home?

When replacing windows, one question often comes up: should you choose double or triple glazing? Triple glazing is sometimes presented as automatically superior. In reality, the best choice depends on the building, its insulation, its orientation and your objectives.

Poorly suited triple glazing does not always deliver the hoped-for gain, whereas high-performance double glazing is enough in many situations. Here are the criteria to examine.

Understanding the Ug and Uw values

Two indicators appear on quotes. The Ug value measures the thermal performance of the glazing alone. The Uw value measures that of the complete window, frame included. The lower these values, the better the insulation.

Triple glazing generally shows a better Ug than double. But it is the Uw value of the complete window, combined with the quality of the fitting, that determines real comfort. Comparing only the glazing is therefore not enough.

Thermal performance

Triple glazing, made up of three panes of glass and two insulating gas fills, limits heat loss more than double. In a new build or a very well-insulated renovation, it logically extends the performance of the envelope.

In a home whose walls, roof and floor remain poorly insulated, the gain provided by triple glazing is by contrast less decisive: the losses then occur mainly elsewhere than through the windows.

Weight and compatibility with the frame

Triple glazing is considerably heavier than double. This extra weight has consequences for the sizing of the frame, the hardware and the hinges, especially for large sashes.

Not all systems are designed to take triple glazing in every dimension. You must therefore check the compatibility of the profile and provide suitable hardware, otherwise adjustments become trickier over time.

Solar gains and daylight

Each pane of glass and each treatment slightly reduces the amount of light and solar heat that enters the room. Triple glazing therefore generally lets through a little less free solar gain than double.

On a south-facing façade, these solar gains contribute to heating in winter. Depending on the orientation, it can make sense to adjust the type of glazing room by room rather than applying the same solution everywhere.

Comfort near the windows

Beyond the figures, triple glazing reduces the sensation of a cold surface near the window. In a room where you often sit close to the glazing — a living room with a large bay, a study corner — this comfort can justify the choice.

High-performance double glazing nonetheless already offers very good comfort in the majority of homes.

Ventilation remains essential

Whichever glazing you choose, highly insulating windows make the home more airtight. Suitable ventilation is essential to remove moisture and avoid condensation. This point should be thought through at the same time as the choice of glazing, not afterwards.

The extra cost versus the real benefit

Triple glazing represents a greater investment than double, both for the glazing itself and for the reinforcement of the frame and hardware it sometimes requires.

The right question is not "which is the highest-performing glazing?" but "which glazing brings the best real benefit for this building, this orientation and this budget?". In a passive house or a very thorough renovation, triple glazing makes complete sense. In a standard renovation, high-efficiency double glazing is often the best compromise.

How to decide?

To guide the choice, it helps to review:

• the overall insulation level of the building (walls, roof, floor)

• the orientation and exposure of each façade

• the dimensions and weight of the sashes

• the compatibility of the profile system

• the ventilation system

• the comfort sought room by room

• the budget available for the whole project

Conclusion

Triple glazing is not systematically the best choice, and double glazing is not a "budget" option. It all depends on the consistency between the glazing, the building and your objectives.

At Pulsar Windows, we do not systematically offer the thickest glazing, but the one that suits your home, its orientation and your expectations. Request your free, no-obligation quote in Brussels or in Flemish and Walloon Brabant.