Are roof windows noisy in rain?
Audible, yes. Loud, rarely. A roof window sits in a slope, so rain strikes the glass at an angle and keeps moving, which is a quite different sound from rain landing square on a flat pane and sitting there. Most people describe it as a wash rather than a drum, and most stop noticing it after the first winter.
Where it deserves proper thought is a bedroom, and particularly a loft bedroom where the glass is a metre and a half from the pillow with nothing between. That is a specification decision made at order, not something that can be added later, which is why it belongs alongside the size and the glazing under VELUX window installation.
Quieter than a flat unit, louder than the tile beside it
Two comparisons frame the whole answer. Against a flat rooflight of the same area, a roof window is noticeably quieter, because a pitched surface sheds and a level one holds a film of water that behaves acoustically like one connected membrane.
Against the roof immediately around it, the window is louder, and that is what people actually hear. A tiled slope over a converted loft puts a tile, a batten cavity, an underlay, 100mm or more of insulation and a plasterboard ceiling between the rain and your ear. The window replaces that entire build-up with a sealed unit around 24mm thick. It is not that the glass is noisy. It is that everything next to it is unusually quiet.
Pitch, and how quickly a drop leaves the glass
Angle changes the energy transfer directly. A drop landing at thirty five degrees gives up part of its momentum along the surface rather than straight through it, then slides. On a fifteen degree slope more of that energy goes into the pane and the run-off is slower, so the surface stays wetter and each subsequent drop lands into standing water.
The practical consequence is that the same window on a Victorian rear addition at forty degrees is quieter than on a shallow modern extension at seventeen. Nobody chooses a pitch for acoustic reasons, but it is worth knowing which end of the range your roof sits at before deciding whether the acoustic glass is worth paying for.
The laminated inner pane you already have
Current roof window panes put a toughened sheet on the outside and a laminated sheet on the inside, because overhead glazing has to stay in the frame if it breaks. That laminated inner is doing acoustic work as a byproduct.
A laminated pane is two thin sheets bonded to a plastic interlayer, and the interlayer converts vibration into a very small amount of heat instead of passing it on. So a modern unit is already better in rain than the single glazed and early double glazed windows fitted across Essex in the eighties, which is one reason a replacement often sounds quieter than expected even before anyone discusses upgrades. Skylight replacement covers what else changes at that point.
The acoustic pane, and the code that names it
Every manufacturer offers a purpose made rain noise pane, and it works on two principles at once. The outer sheet becomes thicker and laminated in its own right, so the surface being struck is heavier and stiffer. And the two panes are made deliberately different in thickness, which stops them resonating together and reinforcing the same frequency.
Manufacturers quote around a ten decibel reduction against the standard pane. Ten decibels is the figure the ear reads as roughly half as loud, which is a genuinely large change rather than a marginal one. It appears in the glazing code, the two digits at the end of the product specification, so a quotation that names a unit without the glazing code has not told you which pane is in it.
A loft bedroom, and the distance to the pillow
This is the case that justifies the upgrade without much argument. In a converted loft the window is in the ceiling plane above the bed, there is no floor void between, and the room is usually small enough to have hard reverberant surfaces close by.
Everything else about a loft works in the same direction. The ceiling follows the rafter line so there is no flat plaster surface to absorb anything. The room is at the top of the house where wind speeds are highest, so rain arrives with more energy. And it is a bedroom, which means the sound matters at two in the morning rather than during the day. A kitchen or a landing under the same window will never raise the subject.
The lining, and the void behind the plasterboard
Part of the sound reaching the room is not coming through the glass at all. It travels through the frame into the trimming timbers and into the cavity behind the internal lining, which is a box of air with plasterboard on one face and can behave like a small drum.
The insulation collar is what deals with it. It is a moulded mineral wool jacket packed between the frame and the trimmed timber, fitted for thermal reasons and doing acoustic work at the same time. Left out, as it often is on a quick fit, you get a cold ring around the window and a lining that rings faintly in heavy rain. Packing that void properly costs very little during installation and is not accessible afterwards, which is the pattern the ten year workmanship guarantee exists to describe.
Run-off leaving the apron onto the course below
There is a second noise that people attribute to the glass and that is not the glass. Water leaving the bottom of the sash crosses the apron of the flashing kit and drops onto the covering below, and a short drop onto a taut sheet of thin metal is audible in a quiet room.
On a plain tile or slate roof it is a non-event, because the apron lies flat on the course below and the water simply carries on down. On a deep profiled tile with a dressed lead skirt it can be more noticeable if the skirt has been left bridging a trough rather than dressed into it. That is a detailing point rather than a product one, and it costs nothing to get right on the day.
The ventilation flap, and the sound it lets in
The flap at the head of the sash opens a controlled slot to outside without opening the window, and it is exactly what you want open on a summer night. It is also a direct air path, and sound follows air.
With the flap open, the glazing specification stops mattering very much, because the rain is arriving through the gap rather than through the pane. In practice the answer is a decent acoustic pane for the nights the window is shut and an honest acceptance that a ventilated room hears the weather. In a room where both matter at once, an electrically operated unit with a rain sensor closes itself as the first drops land, which is a neat resolution and is covered under electric rooflight installation.
Specifying quiet before the order goes in
Write down three things when you enquire: which room the window serves, whether anyone sleeps or works underneath it, and the pitch of the slope if you know it. Those three settle the glazing recommendation without guesswork.
If quiet is a priority, ask specifically for the acoustic pane by its glazing code, ask for panes of differing thickness, and ask that the insulation collar is included and named on the quotation. All three are ordinary items and all three have to be decided before the unit is made. Changing the acoustic behaviour afterwards means a new sealed unit, and that is a decision much better taken in the ten minutes before the order goes in than in the third November.
Tell us about your roof
We start with the building, the covering and the slope. Then we tell you what will suit it, and what it will cost, as a fixed written number.
- Surveyed before it is priced
- 10-year workmanship guarantee
- Building Control notification handled
- New installations and replacements