The third pane cuts heat loss further, keeps the inner glass warmer and can reduce outside noise, but it adds weight, thickness and cost. For most replacement windows, good double glazing already meets the rules, so triple glazing is an upgrade to recommend on the right jobs rather than a default.
Here is how to explain the difference to customers, when triple glazing is worth it, and what to check before you order.
What Is the Difference Between Double and Triple Glazing?
A double glazed sealed unit has two panes separated by a spacer bar, with the cavity usually filled with an inert gas such as argon and a low emissivity coating on the glass. A triple glazed unit adds a third pane and a second cavity, which slows the movement of heat through the unit even more.
The result is a thicker, heavier unit. On our aluminium windows, for example, double glazing is 28mm and triple glazing goes up to 44mm, so the frame and beads have to be specified to suit. That is why it pays to decide on the glazing at the quote stage, not after the order is placed.
How Much More Efficient Is Triple Glazing?
Triple glazing lowers the U value of the window, which is the measure of how much heat passes through it. The lower the number, the better the insulation. The independent body that runs the UK Window Energy Rating scheme, BFRC, notes that triple glazed windows can achieve much higher thermal performance than double glazed windows. It also points out that they let in less free heat from the sun, which matters on south facing elevations.
When you talk numbers with a customer, be clear whether you mean the centre pane figure for the glass or the whole window U value, which includes the frame. The whole window figure is the one that counts for building regulations, and it is the fair one to compare. Our aluminium windows achieve U values from 1.0 W/m²K depending on the glazing specification.
Does Double Glazing Still Meet Building Regulations?
Yes. Under Approved Document L, replacement windows in existing homes in England need to meet a limiting U value of 1.4 W/m²K or a Window Energy Rating of Band B. A good modern double glazed window can meet that comfortably.
This is a useful point for installers. Triple glazing is not something you have to sell to stay compliant on a typical replacement job. It is a genuine upgrade for customers who want more comfort, quieter rooms or better long term performance, and you can present it that way.
“I always tell installers to quote both. Put the double glazed price and the triple glazed price side by side and let the customer choose. Most appreciate being given the option rather than being pushed.”
Scott, Director at Nova Trade Frames
Is Triple Glazing Worth It?
It depends on the property and on what the customer wants from the job. If they are only thinking about energy bills, the payback on triple glazing can be long. The stronger reasons to choose it are comfort, noise and future proofing.
When triple glazing makes sense
Triple glazing is usually worth recommending on north facing or exposed elevations, where rooms feel colder and windows lose more heat. It suits homes near busy roads, railways or flight paths, particularly when combined with acoustic glass. It is a good match for new builds, extensions and deep retrofit projects, especially where the customer has a heat pump or very good insulation elsewhere. And it helps where customers complain about cold spots or condensation on the inside of the glass, because the inner pane stays warmer.
When double glazing is the better choice
Double glazing is often the better quote on south facing rooms, where solar gain helps in winter, and on tight budgets or whole house jobs where the extra cost would be hard to justify. It also makes sense for older or lighter frames and for sashes where the extra weight is a concern, and in rental properties where landlords want compliant, durable windows at a sensible price.
Mixing specifications is perfectly reasonable. Triple glazing on the cold, noisy side of the house and double glazing on the sunny side can give the customer the best of both.
Triple Glazing and Noise Reduction
A third pane does help with noise, but the biggest improvement usually comes from the glass choice rather than the number of panes. Different glass thicknesses and acoustic laminated glass break up sound more effectively than identical panes. If noise is the customer’s main complaint, specify for noise rather than assuming triple glazing alone will fix it.
What Installers Should Check Before Ordering
Triple glazed units are heavier and thicker, so check the practical details before you commit. Confirm the frame system and beads accept the unit thickness, and that hinges and friction stays are rated for the sash weight, particularly on larger openings. Plan handling on site too, as large triple glazed units are a two person lift.
Be careful with glazing into existing frames. Many older frames simply cannot take a thicker unit, so a straight swap is not always possible. If in doubt, ask us before you quote. Our article on common mistakes when ordering trade double glazed windows covers the other errors that slow orders down.
“The question we get most is whether a triple glazed unit will go into an existing frame. Check the frame depth first. It saves a lot of headaches later.”
Scott, Director at Nova Trade Frames
Triple Glazing Options from Nova
We supply double and triple glazed units across our ranges, including aluminium casement windows, Kömmerling casement windows and our uPVC windows supply only range. You can see a real example in our case study on triple glazed units for energy efficiency.
Frequently Asked Questions
Is triple glazing worth it in the UK?
For colder, exposed or noisy rooms, and for highly insulated homes, it often is. For sunny elevations and budget led jobs, good double glazing is usually enough.
Can triple glazing go into existing double glazed frames?
Sometimes, but often not, because triple glazed units are thicker. Check the frame and bead depth before quoting.
Does triple glazing stop condensation?
It greatly reduces condensation on the inside of the glass because the inner pane stays warmer. It will not fix poor ventilation in the room, so ventilation still matters.
Get Triple Glazed Windows for Your Next Job
Nova Trade Frames manufactures uPVC and aluminium windows and doors for the trade in Mansfield, with fast lead times, delivery across the UK mainland and technical support from people who know the products. If you are not sure which glazing spec is right for a job, talk to us before you quote.
Open a trade account or contact the team to price double and triple glazed options side by side.