Electric rooflights out of reach and why they suit

The measurement that settles it, and where it is taken from

Take the distance from the finished floor immediately below the unit to the bottom edge of the sash, and take it after the floor build up, the screed and any raised platform are accounted for.

A comfortable operating height for an adult standing on the floor is around two metres to the grip. Between two metres and about two and a half a pole works and is tolerated. Above two and a half metres a pole becomes awkward, needs both hands, and has to be stored somewhere near the window, which in practice means leaning in a corner. Above three metres it stops being realistic at all.

The measurement is worth taking from the actual position rather than from a drawing, because a stairwell has no single floor level beneath it and the honest figure is the one taken from the highest tread anybody could stand on safely.

The void over a staircase, and why nothing else will do

A stairwell rooflight is the classic case, and it is also the position where the unit does the most good.

A stair core is usually the darkest part of a house, it is landlocked on every side, and it is the top of the building’s warm air column. A rooflight there lights three floors at once and vents the whole house through the stack. It is also directly above a flight of stairs, which means there is no floor to stand on, no safe position for steps, and a fall risk under any attempt to reach it.

Powered operation is not a convenience in that position. It is the only arrangement in which the ventilation the unit was specified for actually gets used. The control goes on a wall at a landing where somebody passes it every day.

Galleried landings, and a unit you can see but not touch

Modern conversions and larger extensions frequently give a galleried landing: a first floor walkway with a balustrade looking down into a hall or a living space, and glass in the roof over the void.

The distance from the balustrade to the sash is often only a metre and a half horizontally, which is exactly the distance that persuades people they can manage with a pole leaned across. Leaning over a balustrade with a two metre pole above your head is the manoeuvre that produces the accident. The rule worth applying is that if reaching the unit involves any part of a person passing over a guard rail, the unit is out of reach regardless of the numbers.

Double height extensions, and glass at the top of a two storey wall

A double height rear extension, whether it is a full height glazed gable in the vale or a two storey addition on a Cheltenham terrace, puts a lantern or a flat roof rooflight four to five metres above the floor.

Two things follow. The unit will be the single most important ventilation opening in the space, because it is at the top of a very tall room and the stack pressure across it is high. And it will be the hardest thing in the house to reach for any purpose at all. Both point the same way. Where the room is being designed, the wiring for the opener costs almost nothing at first fix and is very expensive to add afterwards, which is the argument the roof lantern installation page makes about ordering the opening gear with the frame.

Above a bath, a shower or a kitchen island

These are shorter distances with the same outcome, because the obstruction is on the floor rather than in the height.

A rooflight over a bath is at a perfectly ordinary height and there is a bath between you and it. Nobody is standing in a wet bath to open a window, and nobody should be reaching over a shower screen either. Over a kitchen island the unit sits above a worktop, a hob or a run of pendant lights, and the same applies.

Bathrooms and shower rooms have a second reason for powered operation, which is that they generate more moisture than any other room in the house and need the ventilation most on exactly the mornings nobody has time to think about it. A humidity threshold does that without anybody deciding to. Any electrical work in those rooms is carried out by a qualified electrician, with the zoning of the room taken into account.

Telescopic poles, and the point at which they stop working

A rod is the traditional answer and it deserves a fair hearing, because on the right unit it is perfectly good.

Where it works: a single unit, on a slope, two to two and a half metres to the grip, in a room where the pole can live behind a door. Where it stops working: any unit reached across a void; any unit needing more than one action, such as releasing a lock and then pushing; anything above about two and a half metres, where the pole is long enough that the weight at the far end makes fine control difficult; and any position where the operator has to look directly upwards while pushing, which is unpleasant and unsteady.

There is also the plain behavioural point. A rod ventilation strategy depends on somebody fetching a rod. That happens in the first summer and it tails off.

The vent nobody uses, and what turns up on the reveal because of it

An unused ventilation opening is not a neutral outcome. It has consequences and they arrive in winter.

A loft bedroom or a bathroom generates moisture continuously. Without purge ventilation, that moisture stays in the air until it meets the coldest surface, which in a room with glass overhead is the glass. It condenses there, runs to the bottom of the sash, and collects at the head of the reveal. Over a couple of winters the plaster at the top corners goes darker, then spots, then stains. Owners read that as a fault in the window. It is very often a room with a perfectly sound unit that has not been opened since it was fitted.

Automatic operation on a humidity threshold removes the whole chain, because the room ventilates when it needs to rather than when somebody remembers.

Cheltenham townhouse stairwells, and three or four storeys of Regency

The stairwells in Lansdown, Montpellier, Pittville and the Bath Road terraces are the most extreme version of this in the county, and they are also where a rooflight does the most.

These houses run to three or four storeys with a single open stair from the hall to the top landing, and a shallow lead flat behind the parapet at the top of it. The unit sits on that flat, invisible from the street, lighting a stair core that has no other daylight at all. From the top landing it is often four metres up. From the hall it is ten.

Much of the stock is listed, which affects the finish and the profile far more than it affects the operation. Where the reveal is historic plaster and nothing can be chased into it, a solar unit removes the cable question entirely.

Steep Stroud and Chalford conversions, and reach on a slope

The valley houses through Stroud, Chalford, Brimscombe and Rodborough carry pitches of 45 degrees and upwards, and a steep pitch does something to reach that people do not expect.

On a 30 degree slope, a roof window installed with its cill at a sensible 900mm above the floor has its top rail around 1.9 metres up, and everything is within reach. On a 50 degree slope the same size of unit reaches the same distance up the slope but far more of that distance is vertical, so the top rail finishes at 2.6 metres or more. A centre pivot control bar at the top of the sash is then simply out of reach in a room with an ordinary ceiling height.

That is the point at which either the control moves to the cill, which some ranges allow, or the unit becomes powered.

Gable end heat in a Severn Vale loft, and the unit at the top of the slope

In a converted loft in Longlevens, Hucclecote, Abbeydale or Quedgeley, the hottest air in the room is the layer sitting against the ridge and in the triangle at the gable end. Venting it means an opening high up, which is precisely the opening that is hardest to reach.

This is where the reach question and the ventilation question turn out to be the same question. A unit placed low enough to reach comfortably vents air that was already tolerable. A unit placed where it will actually cool the room is above the reach line by design. Powered operation is what allows the unit to go where the heat is rather than where the hand is.

A timer that opens the unit at ten in the evening and closes it at six in the morning is what turns that into a working night purge, and it runs whether the household thinks about it or not.

Cleaning, and the second reach problem

Operating the unit is one problem. Washing it is the other, and it gets forgotten at specification stage.

On a manual centre pivot the sash rotates through 180 degrees and locks on a barrel bolt, so the outer face can be washed from inside. That only helps if you can reach the sash to rotate it. On a unit above a stairwell, and on any top hung unit, the outer face is unreachable and stays unreachable for the life of the installation.

Two things answer it. A self cleaning coating on the outer pane, which uses daylight and rain to break down and wash off organic soiling, and works best on a slope where water actually runs. And a laminated inner pane, which is required in most of these positions anyway because there is habitable space or a stairwell underneath. The glass specification page goes into the coatings.

Blinds and shading at the same height

Anything the sash cannot reach, a blind cannot reach either, and a rooflight in a stairwell or over a double height space is usually south or west facing because that is where the daylight was wanted.

The result is a lot of solar gain arriving through glass that nobody can shade by hand. Powered blinds in the same channels, driven from the same control, are the normal answer and they are ordered with the unit rather than added afterwards because the fixing points sit inside the frame. They are set out on the internal electric blinds page. The alternative worth considering at the same time is a solar control coating on the outer pane, which reduces the gain before it reaches the room instead of after.

Escape openings that finish out of reach

Where a room in the roof relies on a roof window as its escape opening, the position of that opening is fixed by the regulations rather than by preference: the bottom of the clear opening between 800 and 1100mm above the floor, and at least 0.33 square metres clear with 450mm minimum in both directions.

That band puts the escape unit within reach by definition, which is the point of it. Where a room also has a high level unit for ventilation and light, the two have different jobs and different specifications. The escape window has to be operable by hand by somebody in a hurry and in the dark. The high level unit can be powered, sensored and automated, because nobody is climbing to it in an emergency.