01The range
Some are, and some are not
There is no single answer for the whole brand, because VELUX sells roof windows with different glazing.
VELUX makes a wide range of roof windows, and the glazing is one of the things that changes from one model to the next. Double glazing is the common build. Triple glazed options exist in the range too, offered on selected models and finishes, and the exact list changes as the catalogue is updated. So if you are asking whether VELUX windows are triple glazed, the plain reply is that the choice is yours to make, not that one fixed spec applies to every window.
That matters if you already have a window in the roof. Yours may be an older double glazed unit, a newer one with coated glass, or something else again. The data plate on the top of the frame, visible with the sash open, will give you the type code to check against the maker's literature. Our page on how to find your VELUX window code shows where to look.
We describe the options neutrally and we do not claim any independent rating for them. What we can do is explain what each type of glazing gives you and let you decide whether it earns its place in your room. The wider range is covered on VELUX window ranges explained.
Triple glazing is a choice to make room by room, not a default to accept.
02Glass
What triple glazing is and what it changes
Three panes and two gas filled gaps lose less heat than two panes and one, and weigh more.
A double glazed unit has two panes of glass with a sealed gap between them. A triple glazed unit has three panes and two gaps. The gaps are commonly filled with argon, a heavy gas that slows the passage of heat, and one or more of the panes carry a low-e coating, a thin film that reflects heat back into the room. A warm-edge spacer, the bar that holds the panes apart, keeps the perimeter of the glass warmer than a plain aluminium bar would.
The measure of how fast heat passes through is the U-value, in watts per square metre for each degree of temperature difference. Lower is warmer. A good double glazed rooflight is around 1.0 to 1.4, and a triple glazed one can come in below 1.0. The extra pane also helps with outside noise and cuts the chill you feel standing close to the glass on a frosty morning. Our guide to rooflight U-values explained goes into the numbers.
There are trade-offs. A triple unit is heavier, the frame has to carry it, and the extra pane trims the light that gets through by a small amount. Neither of those is a reason to avoid it. They are reasons to choose with your eyes open.
| Glazing | Typical U-value (W/m²K) | Weight and light |
|---|---|---|
| Double, low-e, argon | about 1.0 to 1.4 | Lighter, slightly more daylight |
| Triple, low-e, argon | below 1.0 | Heavier, slightly less daylight |
03Worth it?
When the third pane earns its keep
Triple glazing pays off in some rooms and adds little in others.
Good double glazing with a warm-edge spacer is enough for plenty of rooms, and it meets the current Building Regulations limit of 2.2 W/m²K for a replacement rooflight with room to spare. Triple glazing begins to make sense where the glass is large, the room faces north, or the space is one where you sit still for hours, such as a loft study or a bedroom you want to keep snug. It also helps in a room that is hard to heat, where every bit of lost warmth is noticeable.
It is a weaker case in a hallway or a landing, where you pass through in seconds, or in a south facing room that gets plenty of winter sun. There the saving is small and the money may go further on a good thermal blind. See VELUX blinds for warmth for how a blind adds a layer of still air on winter nights.
- Large panes or a long run of windows in one slope
- A north facing roof that sees little winter sun
- A room you sit in for long stretches, such as a study
- A bedroom where noise from outside is a bother
- A space that has always been difficult to heat
04Fitting
What this means if you are replacing
The glazing is chosen with the rest of the build, because a warm pane in a cold frame does not help much.
When we replace a window, frame and glass together, we treat the whole opening. That means the flashing, the insulation around the frame and the lining inside, as well as the pane. The work is a controlled fitting under Part L, so the new window has to meet the current limit and we handle the Building Control notification where the work is notifiable. A new window with a matching flashing kit, as set out in VELUX flashing kits explained, is what keeps the opening dry as well as warm.
If only the sealed unit has failed, the old frame may stay. If the frame has gone, replacing the window as a whole is the straight answer. Our guide to replacing an old rooflight explains the difference. Whichever you need, we fit warm-edge glazing as standard, and a free survey and written quote from Radiant Skylights will lay out the glazing options for your roof. The wider range of windows we fit sits on our VELUX windows page.
Is triple glazing on a VELUX worth asking for?
Can I upgrade my existing window to triple glazing?
Not by swapping one pane. The sealed unit and frame are made as a pair for each model, so an upgrade usually means a new window. We will confirm what suits your opening at survey.
Does triple glazing cut outside noise?
The third pane can reduce outside noise a little, and rain on the roof can sound more muted. It is a side benefit and not the main reason to choose it.
Does triple glazing stop condensation?
It warms the inner pane, which makes condensation less likely. A warm-edge spacer and good ventilation matter too, because damp room air is the root of the problem.
Will triple glazing make the window heavier to open?
The sash weighs more, and the hardware is built for the model it is sold with. Choose the type that suits how you use the window, and ask us if you are unsure.
