Double or triple glazing?

Choosing between double vs triple glazing comes down to how much extra warmth and quiet you need, and whether it is worth the extra weight and cost. All our windows are A-rated as standard. Triple glazing adds a third pane for extra warmth and quiet.

This guide explains how each option is built, what the real differences are, and where triple glazing earns its place.

Double glazing

Our standard 28mm sealed units use two panes of glass, a warm-edge spacer and argon gas between the panes. This is the right choice for most homes.

The argon gas is denser than air, so it slows down heat moving from the warm inside pane to the cold outside pane. The warm-edge spacer keeps the edges of the glass warmer, which reduces the cold line and condensation you sometimes see around older units.

A good A-rated double glazed window is a big step up from old double glazing fitted in the 1980s and 1990s, which usually had air-filled units and aluminium spacers. For most people replacing tired windows, it gives the biggest improvement for the money.

Triple glazing

Triple-glazed units add a third pane. They lose less heat, reduce outside noise and cut condensation on the inside pane. They are heavier and cost more, so they make most sense on north-facing rooms, busy roads and very energy-efficient homes.

With two gas-filled cavities instead of one, the inside pane stays closer to room temperature. That means fewer cold spots near the window and less chance of condensation forming on the glass in winter.

Double vs triple glazing compared

	Double glazing	Triple glazing
Panes of glass	Two	Three
Gas-filled cavities	One	Two
Heat loss	Low	Lower
Inside pane temperature	Warm	Warmer, less condensation
Weight	Standard	Noticeably heavier
Cost	Lower	Higher
Best for	Most homes	Cold, noisy or very efficient homes

Building Regulations and energy ratings

Replacement windows in England must meet Part L of the Building Regulations, which sets a limit on how much heat a window can lose. This is measured as a U-value: the lower the number, the better the insulation. Window Energy Ratings (WER) give an easier A to G style guide that also takes solar gain into account.

A-rated double glazing comfortably meets the requirements for replacement windows. You do not need triple glazing to comply, so treat it as an upgrade rather than a necessity.

When triple glazing is worth it

• North-facing rooms that get little sun and feel cold near the glass.
• Homes on busy roads, where the extra pane and cavity help reduce noise.
• Well-insulated or low-energy homes, where the windows are the weakest point in the building.
• Large areas of glass in living spaces where cold radiating from the window is noticeable.

When double glazing is the better choice

• South-facing rooms, which benefit from free warmth from the sun through the glass.
• Large opening sashes, where extra weight means more strain on hinges and handles.
• Projects on a tighter budget, where the money is better spent on more windows or better insulation elsewhere.

Noise: triple glazing is not the only answer

If noise is your main problem, triple glazing helps, but it is not always the best option. Acoustic glass uses a special laminated interlayer and different pane thicknesses to break up sound. Read our guide to acoustic and laminated glass to compare the two before you decide.

Will it fit my frame?

Yes. Triple glazing is made to fit the same frames we supply, so you can choose it on any window in the designer.

If you are replacing glass in an existing frame rather than buying a new window, the unit must match the gap in your frame. Our guide to sealed unit thickness and spacers explains how to check this. You can also order triple glazed units or A-rated double glazed units on their own.

Common mistakes

• Assuming triple glazing is needed to pass Building Regulations. It is not.
• Fitting triple glazing in an old, draughty frame. Good seals and a sound frame matter as much as the glass.
• Choosing triple glazing purely for noise without comparing acoustic glass.

Quick answers

Is triple glazing much warmer than double glazing?

It loses less heat and keeps the inside pane warmer, so rooms feel more comfortable near the glass. The difference is most noticeable in cold, north-facing rooms.

Does triple glazing stop condensation?

It greatly reduces condensation on the inside pane because the glass stays warmer. Good ventilation, such as trickle vents, still matters.

Is triple glazing heavier?

Yes. The third pane adds noticeable weight, which is worth bearing in mind on large opening windows.

Are all your windows argon filled?

Yes. Every window we make is A-rated with argon-filled glazed units.

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