The short answer
Yes, a Velux can go in during winter, provided the work is planned around the weather. Cold is not the problem. Rain, snow and strong wind are, because the roof is open while the old window comes out and the new one goes in. A good fitter picks a dry day, has temporary covers ready and does not start an opening that cannot be closed in before dark.
Winter fitting is a matter of forecasts and preparation. A roof window opening is only exposed for a short stretch, and it should be sealed in every evening.
Why a dry day matters more than a warm one
An opening cut for a roof window is a hole in the weather layer. The covering is cut back, the underlay beneath it is trimmed, and the old frame is lifted out. Underlay is the sheet that lies under the battens and catches stray water. Until the new frame is in, only a temporary cover stands between the room and the sky.
What weather stops a window job?
Steady rain and sleet stop it, because water runs straight down the rafters into the room. Snow does the same once it melts. Strong wind is the less obvious one. A large new sash is a sail on a sloping roof, and lifting it on to the slope in a gusty hour is unsafe for the person on the ladder as well as for the glass.
Cold on its own matters little to the fitting. The frame, the flashing and the membrane do not mind a chilly morning, and the fitting itself is no harder in the cold. What we watch for is wet timber and frost on the slope, because a ladder on a frosty slate has little grip, and a damp batten is a poor base for a new frame.
How the opening is kept weathered between stages
Every roof window job should leave the opening closed in by evening, whatever the season. In winter that routine matters more, since the nights are long and the forecast can turn.
What does temporary weathering look like?
It means a sheet of tarpaulin or heavy polythene tacked over the opening and tied back over the ridge or battened down to the slope, with the edges tucked under the covering above so water runs off it rather than into it. If the new window is in place but the flashing is not yet complete, the frame is covered the same way. Nothing is left flapping, because a loose sheet in a gale does more harm than none.
We also set the pace of the job so the opening spends as little time as possible exposed. The window and flashing kit are on site and checked before the old frame comes out, so nothing is missing mid-job. Our answer on what happens on installation day walks through that sequence in more detail.
Watching the forecast and moving the date
The honest approach to winter work is to treat the booked date as provisional. A week of settled weather in January is not unusual in Somerset, and so is a week of low cloud and showers rolling in off the Atlantic, and the fitter should be ready for either.
Will my fitting date move?
It may, and a good fitter will tell you so early. We look at the forecast the day before and again that morning. If rain is due before the opening can be closed in, we move the job to the next dry window instead of starting and hoping. You will hear from us before anyone arrives on site, and the new date is confirmed in writing.
There are practical steps on your side too. Clear the room beneath the window the night before, mention any awkward access, and move anything valuable out of the loft. If the window has a deadline behind it, such as a loft conversion programme, say so during the survey and the timing is planned around it. Our general page on roof windows and skylights sets out how a fitting is organised.
When it is better to wait for spring
Some windows are best left until the weather settles, and a fitter who says so is doing you a favour. A large new opening in a steep slope, a pair of windows side by side that open up a wide section of roof, or a window above a room you cannot move out of for a night: each of these carries more risk in a wet month.
Is it worth waiting for a new opening?
If the roof is watertight now and the window is a comfort rather than a repair, waiting a few weeks costs nothing. If the old window leaks, the picture changes. A leaking roof window is better dealt with soon, and a leak gets a temporary make-safe first, so you are not sitting with damp while you wait for a settled spell.
The same goes for a swap in the existing opening. That is a shorter job with a smaller area open, so it copes with a typical winter far better than a new hole. Either way, the survey tells us what we are dealing with, and one written price follows it. We look at the slope, the covering and the access, then talk the timing through before any date is fixed.
More on winter window fitting
What happens if it rains while the old Velux is out?
The opening is covered straight away with a tarpaulin tucked under the course above, and the job stops until it is dry. That is why we only start when the forecast gives us time to close in. A window that is out and not yet replaced is never left uncovered.
Does cold weather affect the new window itself?
Not in a way you would notice from the fitting. The frame, glass and flashing are made to sit outdoors in all weathers. The risks in winter are wet timber, frost on the slope and wind while lifting, and those are managed by choosing the day and the time of day carefully.
The full picture: Velux roof window and skylight installation in Taunton ยท More short answers