Roof windows in a bedroom and blackout

Why a bedroom under a slope behaves differently

A wall window faces one compass direction and sees roughly half the sky. A roof window faces the whole dome of it, so it collects light earlier, keeps it later, and admits far more of it for the same area of glass.

In a living room that is the reason to fit one. In a bedroom it is a specification problem. The same geometry that makes a loft bedroom bright and pleasant at ten in the morning makes it bright and unpleasant at half past four in June, and it also means the room gains heat from above on a summer afternoon while the rest of the house stays cool. Both are solvable. Neither solves itself.

Sunrise on an east facing slope, and the dates that matter

In Essex the sun clears the horizon at around 04:35 in the third week of June, and the sky starts lightening close to an hour before that. On an east or north east facing slope, direct sun is on the glass within minutes of sunrise because there is no wall above the window to shade it.

The period that causes trouble runs from roughly late April to mid August, when sunrise is before six. Outside that window an ordinary lined curtain over a wall window would cope. Inside it, a roof window without proper blackout wakes people, and it wakes small children who then wake everybody else. The decision is made for eight weeks of the year and lived with for the other forty four.

Choosing the slope the bedroom window sits in

Where there is a choice of elevation, and in a loft conversion there often is, the compass points matter more than the view.

A north facing slope gives steady, cool, shadowless light, almost no solar gain and no early sun at all. It is the easiest bedroom elevation by a distance. West is next: hot late sun in the evening, which is manageable because the room is not in use, though the heat is still in the fabric at bedtime. East delivers the early wake up. South collects the strongest overhead gain and needs solar control glass as well as a blind. Where the window has to go on the east or south slope, the blackout and the glazing are specified together rather than one after the other.

What blackout means on a window that is not vertical

A blackout blind for a roof window is a fabric with an opaque backing, running in aluminium side channels fixed to the frame, with a bar at the leading edge that locks at any position on the run.

The channels do two jobs. They hold the fabric flat against a surface that gravity is pulling it away from, and they close the gap at each edge where light would otherwise track down. Without them the fabric bellies away from the glass in the middle and glows at the sides. This is why a roof window blind is a different product from a wall blind rather than the same thing in a different size, and why the general question of which blind suits which room is covered separately on our page about blinds for roof windows.

The edge of the blind, and where light gets past it

Even a good channelled blackout blind is not a photographic darkroom, and it helps to know where the remaining light comes from so expectations are set.

There are three routes. A hairline at the top where the fabric enters the head box, a thin line at each channel where the fabric meets the aluminium, and a gap at the bottom bar unless it is pulled fully down to the cill stop. In a room painted white, that small amount of light bounces and reads brighter than it is. Painting the reveal a darker tone makes a measurable difference to how dark the room feels for no cost at all.

Ordering the provision with the window rather than after

The brackets a channelled blind clips into are part of the frame. Most current roof windows have them pre fitted as recesses or clip points in the top of the frame, and the blind pushes into them without tools.

Older units, and some entry level ranges, do not. Retrofitting to those means an external cassette, a face fixed alternative that sits proud of the reveal, or living with the compromise. The blind does not have to be bought at the same time as the window, but the provision has to exist. The moment to check is at order, when the model code is being confirmed and the cost of getting it right is nil.

Motorised blackout in a room people sleep in

Electric blinds make sense above about two metres of reach, and in a bedroom there is a second argument for them: a blind on a timer closes at dusk and opens at a chosen hour, which turns a roof window into a gentle alarm clock rather than an aggressive one.

The point to raise before ordering is noise. A motorised blind running at six in the morning is audible in a quiet room, and solar powered units with their small motors are generally quieter than mains ones. Where the window itself is motorised as well, the blind and the opener can share a control and a single cable run, which is worth deciding before the ceiling is boarded.

Night temperature in a room directly under the tiles

A loft bedroom sits under a roof that has been absorbing sun all day, and the heat arrives late. The room is often at its warmest between nine at night and one in the morning, several hours after the peak outside.

A blackout blind pulled down during the day helps, because it stops solar energy reaching the room in the first place, but a fabric blind on the inside is always the second best place to stop heat. The glass has already let the energy in. That is why on a south or west facing bedroom slope the glazing specification comes first, with a solar control coating bringing the g-value down, and the blind handles darkness rather than temperature.

Getting warm air out before bedtime

The useful property of a roof window in a warm bedroom is that it sits at the highest point in the room. Warm air collects there, and an opening at that level lets it leave while cooler air comes in through a window lower in the house.

Practically that means opening the roof window in the early evening, with a door or a landing window open, and closing it before sleep. A ventilation flap in the frame lets a background flow continue overnight without the sash being open, which matters at ground accessible level and in bad weather. A rain sensor on a motorised unit closes it automatically, which is the honest answer for anybody who wants to sleep with an open roof window in an English summer.

Rain directly over a bed, and how it sounds

Rain on glass is louder than rain on tile, and a bed is usually a metre or two below the opening with nothing in between. Most people describe it as pleasant for the first winter and less so by the third.

Two specification choices reduce it and both are made at order. A laminated outer pane damps the drumming because the interlayer absorbs the vibration a single sheet transmits. An asymmetric unit, with the two panes at different thicknesses, breaks up the resonance instead of reinforcing it. In a bedroom, laminated glass is often being specified anyway for safety reasons, so the acoustic benefit comes as part of the same decision.

Overnight moisture, and the misting people find at breakfast

Two adults asleep in a room put out something in the order of half a litre of water vapour overnight. In a small loft bedroom with the door shut, that has to go somewhere, and the coldest surface in the room is the roof window.

Condensation on the inside of the glass on a cold morning is physics rather than a fault. It is reduced by a warmer inner pane, which means better glazing, and by background ventilation, which means the flap in the frame left open or a trickle path elsewhere. Condensation between the panes is a different matter entirely: that means the sealed unit has reached the end of its working life and wants replacing.

Where the window should land relative to the bed

Directly over the pillow is the position people regret. Morning light lands on a face, rain is loudest at the head end, and any condensation drip finds the bedding.

Over the foot of the bed or to one side is better on all three counts and gives a better view from sitting up. In a loft with a knee wall, placing the window in the sloping ceiling on the side of the room the bed does not occupy tends to produce a room that works. The related question of how high the bottom of the window sits is set out on our page about cill height and the view out, and in a bedroom it is answered from lying down as well as standing up.

Escape from a loft bedroom, in one paragraph

A habitable room in a loft conversion generally needs either a protected stair or an escape window, and where a roof window is doing that job it has to meet a minimum clear opening and sit within a defined height band above the floor. The requirements, the sizes that satisfy them and the units that do not are set out on our page on escape openings and the rules. The point to carry into a bedroom conversation is that a blackout blind and a child restrictor both sit on a window that may also be an escape route, and the three specifications are settled together.

Outside noise, and what the glazing changes

A bedroom under a roof hears things a ground floor bedroom does not. Aircraft on the Stansted and Southend approaches, the A12 and A120 on a still night, and gulls on the coastal side of the county from first light.

Acoustic laminated glass in the outer pane is the effective specification and it is available across the main ranges as a standard option. The interlayer is thicker and softer than the safety grade and it damps a useful band of traffic and aircraft noise. It is ordered with the unit, it costs a fraction of the installation, and it cannot be added to a window that is already in the roof.

Cables in a bedroom ceiling, and the moment to run them

Anything motorised in a bedroom, whether the blind, the window or both, wants a cable, and the cost of that cable is entirely determined by when it is decided.

Run at first fix, while the rafters are open and the plasterboard is in a pile downstairs, it is minutes of work. Retrofitted, it means lifting boards, chasing plaster or a surface trunking run down a sloping ceiling in full view. Solar powered units exist precisely to avoid this and they are the sensible answer on a conversion that is already finished. On a new conversion, run the cable even if the motor is fitted later.

Curtains and pelmets, and why gravity defeats them

People ask about curtains over roof windows because curtains are what bedrooms have. On a slope they hang away from the glass at the angle of the pitch and do very little.

Where a bedroom has both a roof window and a wall window, the two get different treatments and the room has to be decorated with that in mind. A blind in the roof plane and curtains at the wall opening read as intentional if the fabrics relate to each other and as an accident if they do not. Where a pelmet or a shelf is being built under a roof window for decorative reasons, it has to clear the sash through its full sweep, which on a centre pivot unit is a larger arc than most people picture. Our roof window installation surveys mark that sweep on the wall so a joiner is not guessing.