VELUX Window Installation in Bristol A window in the slope, with a handle you can reach

This page covers VELUX window installation in Bristol: what the range offers, how we choose a size, how a window goes into an existing roof, the electric and solar versions, and the rules behind it all. Roof windows from every maker are covered on our roof windows page. Here we stay with the VELUX range.

Why a window in the slope earns its keep

A window in the slope looks up and out rather than straight across. That means it picks up sky light, which is brighter than the light that comes through a wall window, and it throws that light a long way into the room. A loft bedroom lit only from the gable end can be gloomy at the far wall.

The window also airs the room. Warm air collects under a sloping ceiling, and an opening sash lets it go. On a still evening, a tilted sash with a vent bar (a small catch that holds the sash open a finger's width) lets air move through the night without leaving the roof open to the weather. Some models open at the top and the bottom, so you can set the sash to whatever the weather allows.

The two jobs we are asked to do

The work falls into two kinds. One is a like-for-like replacement of a window that has misted, jammed or worn out, where the opening in the roof already exists and the new window goes into the same hole. The other is a new window in a roof that has none, which means cutting through the tiles, trimming the rafters and lining a fresh reveal. Both are building work, and both are planned the same way: survey first, then a written quote that shows the size, the glass, the opening type and the finish, side by side.

Sizing is where people get stuck, because the catalogue speaks in codes. A width letter comes first and height digits follow, so MK04 and MK08 are equally wide but not equally tall. Our guide to VELUX size codes sets out how to read them.

From here the page follows the decisions in sequence: how to size and place the window, which opening and power type to choose, the glass and the finishing touches, how long a window lasts and when to replace it, and the regulations and costs behind the work. If you are weighing a window against other kinds of opening glass, fresh air rooflights shows where opening helps and where fixed glass is the better choice.

Height off the floor

Position matters as much as size. In a loft room, the window should sit where you can reach the handle and still see out when you are standing. In a room with a low eaves wall, a window set too low can leave you looking at the gutter. Set too high, the handle is out of reach and the view is nothing but sky. A top-hung window with the handle on the bottom bar is easier to reach than a centre-pivot with a high handle, which suits a taller room.

For a stairwell, the opposite applies. A window set high in the slope above a stair throws daylight down into the hall, and you never need to reach it, so it can be an electric model with a wall switch. That is a neat answer for a landing on a two-storey Edwardian house.

Rafters and the opening

Rafters in older Bristol roofs are not always evenly spaced. We measure the gaps in the loft with a tape, and we look for purlins (horizontal timbers that support the rafters) that might sit in the way. If a timber has to be cut, trimmers are fixed either side to carry the load.

The lining of the reveal decides how the window looks from inside. It runs from the frame to the ceiling at an angle, so light spreads into the room instead of falling into a dark box. Where new insulation sits over the rafters the reveal gets deeper, and a deep reveal throws less light than a shallow one.

Slope counts too. A shallow pitch needs a particular flashing, and sometimes a different glazing build, so we check the pitch on the roof and choose to suit. The quote notes where each window sits and which way each sash opens.

Matching what is already there

Where a house has a row of old windows, the new one should line up with them in height along the slope and in width. On a terrace, matching the neighbours also keeps the street looking tidy, and in a conservation area it can be a condition of consent, as in Bath.

Electric or solar

The electric version runs from the mains through a cable to the frame, which is simple in a new loft conversion and more disruptive in a finished room. The solar version carries a small panel built into the frame. It charges a battery, so no cable runs through the ceiling. That suits a landing that has just been decorated.

Both take a remote. The rain sensor sits on the frame and shuts the sash at the first drops, which makes an electric window feel safe to leave open when you go out.

Where opening helps, and where fixed is fine

An opening window earns its place in a bathroom, a kitchen, a loft bedroom and a landing. Steam leaves a bathroom through the top, a kitchen sheds cooking heat, and a loft bedroom gets the cross-flow of air that makes sleeping in summer more comfortable. A fixed window is the right answer where the room is already aired by other windows, or where you want the slimmest frame and the lowest price. A stair that already has a half-landing window may not need an opening unit at the top.

We show the opening choices on every quote, so you can see what each costs. Fixed, manual, electric and solar sit beside each other with a plain note on what each adds.

Ventilation rules

Part F lets a sash that opens count towards purge ventilation, the rapid airing that clears steam or cooking smells. That helps in a loft conversion where the window may be the only opening. Opening windows help air a room and can help condensation clear, but they work alongside other ventilation, not in place of it.

For a bungalow or chalet bungalow, an opening roof window may also serve as an escape window for the rooms in the roof. The guide to a VELUX window in a bungalow works through them. On a two-storey house, an escape roof window is not the answer for a loft conversion: it needs a protected stair.

Wiring needs thought. We plan the cable route, switch position and supply at the survey, and note them on the quote.

The choices in blinds

• Blackout. Closes the window to near darkness. The choice for bedrooms and nurseries.
• Roller. A slim fabric roller that runs in side rails. Good for filtering the glare in a study.
• Pleated. A folding blind that can be stopped at any point, with a top-down option to let in light while covering the lower view.
• Outside awning. Fixed on the outside of the glass, so it stops the sun before it enters the room. It costs more and does more.

Outside blinds and shutters are the strongest answer to heat on a south or west facing slope, because the sun's heat is stopped before it reaches the glass. Indoor blinds soften the light but the glass has already taken the heat. A loft bedroom that bakes in July is a good candidate for an outside blind.

Flashings, linings and trim

The flashing is the metal trim that surrounds the window and carries water over the tiles. It is made in kits for each size and roof covering, whether plain tiles, interlocking tiles, slate or a profile. A Bath stone house with stone slates needs a different kit from a 1960s house with concrete tiles. The right kit matters because the flashing is what keeps the weather out for years after the day we leave. We choose it at the survey and name it on the quote.

Inside, the lining is the white panel that closes off the gap between the frame and the plaster. It can be supplied in a white-painted finish, or in unfinished wood to be painted or stained. If the room has dark pine or a coloured scheme, the lining can follow it.

Other accessories

An insect screen is a good idea in a kitchen or bedroom where the window may stay open in summer, and a pole makes a manual window usable one step above head height. We list accessories on the quote as separate items, so you can see the choices and add or leave out each one.

The way a blind is fitted depends on the window. An inner blind clips into the frame and needs nothing but a few screws. An outer blind needs a fixing on the roof and, if powered, a cable or a solar panel. We fit them at the same time as the window when you want them, which saves a second visit and a second set of ladders.

Colour and fabric are best seen in the room. Samples are small, and a fabric looks different in daylight from above than it does under a kitchen light. Bring a few to the roof window at midday if you can, and look at them against the glass before choosing.

Signs that a window is near the end

1. Mist or droplets appear between the two panes of glass and do not wipe away. That is a sealed unit that has failed.
2. The sash no longer sits flush against the frame, or the handle is stiff and the hinges drag.
3. A draught or whistle comes round the closed sash, which points to a worn gasket.
4. Staining or damp shows on the lining below the window, which suggests the flashing or the seal has aged.
5. The motor on an electric model stalls or the rain sensor stops responding.

None of these means the whole window needs to go. A failed sealed unit can sometimes be replaced inside a frame that is otherwise sound. Replacing only the sealed glass unit in an existing frame generally is not notifiable building work. But a frame that has aged badly, or a window that no longer has the performance of a modern one, is better replaced whole.

Replacing the glass or the whole window

A whole new window, frame and glass, counts as notifiable building work, so we make the Building Control notification for you. Our page on misted and failed rooflights covers the glass-only route in detail, and explains how to tell whether the frame beneath is worth keeping.

What a new window brings

The standard is higher now than when older windows went in. Part L 2021 sets an existing-dwelling roof window at 1.4 W/m²K or Window Energy Rating Band B. A window from twenty years ago may be well short of that, and the difference can show as a cold spot above the bed in January. For what the numbers mean, see energy-efficient rooflights.

Newer windows also come with better seals, easier cleaning and a handle that falls to hand. The glass can be toughened, laminated or coated for sun. No law asks for a laminated inner pane in a house roof (Part K is silent on it), so it stays a recommendation that we price beside the plain option.

Timing a replacement is a matter of choosing a dry spell, when the opening will be exposed for the shortest time. Whatever the stage of the job, the roof is closed up and watertight by evening.

If you are unsure whether a window is ready for replacement, the free survey will tell you. We look at the frame, the seals and the glass, check the flashing from the roof, and write down what we find. No obligation follows, and the quote lists each option with its price so you can decide at your own pace.