Are VELUX Windows Triple Glazed?

Standard glazing and the triple option

A roof window arrives with whatever glazing its model code specifies. The name on the box does not say whether there are two panes or three, so you need to look at the product details. Across the VELUX family, double glazing is the familiar build. A number of ranges also offer a triple glazed pane as a choice, and that is something to ask for before the window is ordered, because the glass cannot be changed on the day.

Product ranges change from time to time, so we check the current specification of the exact model before quoting rather than relying on memory.

What a third pane does

An extra pane adds a second sealed gap between layers of glass. Less heat passes through the window, so the inner surface stays warmer on a cold night. That can mean less condensation on the glass and a more comfortable spot to sit in beneath it.

It also reduces noise a little, which can matter on a road with passing traffic or under a flight path. The gain is modest, not dramatic, so a window that is noisy for other reasons, such as rain on the outer pane, will still sound like a roof window.

What it costs you in other ways

More glass means more weight. The sash is heavier, the hinges work harder, and some manual models feel stiffer to open and close. It also generally thickens the glass unit, so the window sits slightly deeper in the frame. None of this is a reason to avoid triple glazing, but it is worth knowing before you choose.

• A heavier sash can suit a window you open rarely and fall short on one you open every morning
• Electric and solar operated windows are built to carry the weight of the option you choose
• Extra layers lower the amount of light that passes through, though only slightly

The rules your window has to meet

For an existing home, Part L 2021 asks a replacement roof window to reach a U-value of 1.4 W/m²K or Window Energy Rating Band B. Plenty of double glazed roof windows meet this, so triple glazing is not the only route to compliance. It is a way to go beyond the minimum if you want a warmer room.

Swapping the entire unit, frame as well as glass, is a controlled fitting and notifiable under the Building Regulations. We take care of the notification, and the paperwork reaches you at handover.

Rooms where a third pane pays off

These are the rooms where the extra pane is most worth a conversation:

• A bedroom in the roof, where a chill coming off the glass is noticeable from the pillow
• A home office, where you sit still in one place for hours
• A north-facing slope that never catches the sun
• A room at the end of a terrace where noise from the street carries up

In a landing or a utility room that you only pass through, the standard double glazed pane will usually do the job well.

The inner pane

Whatever the number of panes, the layer facing the room is a choice of its own. For the pane that faces the room we pick laminated glass, because overhead safety matters and a laminated pane stays in one piece if it cracks. Building Regulations do not require this under Part K, but it is the sensible choice above a bed or a desk.

Triple glazing and condensation on the inside

A pane that is warmer on the room side is less likely to collect moisture, but glass is only one part of the story. Condensation forms where warm, damp air meets a cold surface, so a steamy bathroom or a bedroom drying washing will still mist a window, however many panes it has. Good ventilation and a window that can be opened a little will do as much as the glass.

The frame matters too. An insulation collar fitted snugly round the frame stops cold bridging through the timber, and it is one of the hidden parts we photograph before the lining goes on.

Check what you already have

If you are curious about your current window, the data plate on the frame tells you the model and size code. The plate sits on the frame and shows once the sash is open, and reading the data plate explains where to look.

If the glass has misted between the panes, the sealed unit has failed, and our misted and failed rooflights page explains the options.

Choosing at the survey

Glazing is easiest to settle once someone has seen the room. When we visit for the free survey, we note the slope, what the room is for and where the sun falls, then put the options in the written quote as separate lines. That way you can see exactly what a third pane adds and decide with the figures in front of you. The fit itself follows a plan for each day: floors and furniture covered, the roof weathertight each evening, and one team from start to finish.

For the wider picture on supply and fitting, see our VELUX window installation page, and our VELUX window cost guide for how the options affect the total.