Gloucester · Cheltenham · Stroud · the Cotswolds

Electric and Opening Rooflights

An electric rooflight is a rooflight you can open from where you are standing, which sounds like a convenience and is usually a necessity.

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15 years in Gloucestershire
10-year workmanship guarantee
Building Control notification handled
The roof is never left open overnight

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What the job covers

The decisions that get made before anything is ordered.

Why installations fail

The unit is the small half of the job.

A powered unit is an ordinary rooflight with a mechanism and a cable in it, and both are decided before the opening is formed. Four things get settled at first fix, because none of them can be revisited once the ceiling is on.

The cable route. Run at first fix, because the ceiling closes over it.
The actuator. Chain, spindle or linear, chosen for the sash weight and the reach.
The seal under power. A gasket that compresses evenly every time the motor closes it.
What happens in a cut. A manual override, or a unit that stays shut when the power does not.

That is what the ten-year workmanship guarantee is written against.

Sealed unit, seated on the frame and never on the covering.
Insulated kerb, 150mm from the finished surface to its top edge.
Covering dressed up the kerb face and closed under the frame.
Deck and roof structure. The kerb is fixed to this, not to the deck alone.

The upstand in section. 150mm measured from the finished roof surface to the top of the kerb, with the covering dressed up the kerb face and terminated under the frame rather than stopped short of it. Almost every flat roof rooflight leak we are called to is this junction, not the glass.

How it runs

Two figures, and no surprises between them.

Send photographs A few pictures of the roof and the room, and rough measurements. An indicative range comes back by email.
The survey Forty minutes on site. Rafter centres, pitch off a digital level, the deck, the fall, and how a scaffold reaches the elevation.
A fixed price Written against what was measured, not against the drawing. It does not move unless you change what you asked for.
The installation Scaffold, opening, kerb, unit, weathering, reveal and making good. The roof is never left open overnight.
Notification and guarantee The Building Control notification is submitted and closed out as part of the job, and the workmanship carries ten years.

Asked before every job

The questions that come up first.

Can rooflights be opened electrically?

Yes. Almost every category of glazed unit that goes into a roof is available with a motor in it, and the electric version is a standard catalogue item rather than a special order. Manufactured roof windows from VELUX, Fakro, Keylite and Roto all have electrically operated variants of their normal size range. Made-to-size flat roof rooflights can be ordered as…

The full answer

How much does an electric rooflight cost?

No figure is published on this site for an electrically operated rooflight, and the reason is that the motor is rarely the expensive part. The difference between a manual unit and the electric version of exactly the same size is a known increment set by the manufacturer. What actually moves the total is everything arranged around it: whether the room…

The full answer

Do electric rooflights need an electrician?

A mains powered rooflight does. A solar one does not, because nothing in it is connected to the house supply at all. That single distinction answers the question for almost every job, and it is worth settling early because it changes how a project is sequenced and who needs to be on site and when. Where a 230V supply is…

The full answer

Can you convert a manual rooflight to electric?

Often yes, and the answer is decided by the model rather than by how much effort anybody is willing to put in. Current generation manufactured roof windows from VELUX, Fakro, Keylite and Roto mostly have a retrofit opening kit designed for them: an actuator that clips into the top rail of the existing sash, a control board, and a remote…

The full answer

What happens to an electric rooflight in a power cut?

Nothing moves. The sash stays exactly where the power left it: closed if it was closed, open if it was open, and part way if the supply went during a cycle. An electric rooflight has no spring in it and no stored energy in the drive, so a cut does not cause it to fall shut or drift open. That…

The full answer

Do electric rooflights close automatically in rain?

Yes, where a rain sensor is fitted, and on manufactured electric roof windows it is fitted as standard rather than as an option. The sensor is a small pad on the outside of the sash, the unit reads it continuously, and the closing cycle starts within a few seconds of the first drops landing on it. Made-to-size opening rooflights on…

The full answer

Are solar powered rooflights any good?

They are, and in a room that is already finished they are frequently the better specification rather than the compromise one. A solar rooflight uses the same chain actuator, the same rain sensor, the same locking drive and the same remote as its mains equivalent. The only difference is where the current comes from: a small photovoltaic panel on the…

The full answer

How long do electric rooflight motors last?

Longer than the glass in most cases, and longer than people expect. A chain actuator in a manufactured roof window is a low duty device: it runs for twenty seconds or so, a handful of times a day at most, and then sits still. Manufacturers rate them in cycles rather than years, and the cycle counts quoted are high enough…

The full answer

The technical detail

Opening glass, wired before the roof closes.

An electric rooflight is a rooflight you can open from where you are standing, which sounds like a convenience and is usually a necessity. The question that decides it is not preference, it is reach: how far above the floor the handle sits, and whether anybody is realistically going to get to it twice a day for the next twenty years. Severn Skylights Gloucester fits electrically operated roof windows and made-to-size opening rooflights across Gloucestershire, on mains supplies and on solar, with rain sensors, wall controls and handheld remotes, and the wiring, the actuator position and the control location are all set out at survey rather than sorted out on the day. This page covers the mechanisms, the power, the regulations that bite on an opening unit, and the parts of the county where the roof or the room forces the answer. The full range of work sits on the rooflight and skylight services hub.

31 sections 33 minute read

Reach is the deciding factor, and there is a line at about 2.3 metres

A manually operated roof window is opened by a bar or a handle at the head of the sash. Standing on the floor, an adult of average height can work that handle comfortably while the top of the frame is up to roughly 2.1 to 2.3 metres above floor level. Above that, a telescopic rod extends the range to something like 3.3 to 3.5 metres, and above that the honest answer is that nobody is going to bother.

In a loft conversion the numbers stack up quickly. A room with 2.4 metres of headroom at the ridge, a 40 degree pitch and a window set two thirds of the way up the slope puts the handle around 2.5 metres above the floorboards. That is a rod job at best. Put the same unit over a stairwell where the floor beneath it is the landing one storey down, and the handle is four metres up with a flight of stairs underneath. There is no ladder position and no rod length that makes that safe, and an electric opener is the only sensible specification.

So the survey measures it. Floor to frame head, vertically, with the pitch and the sash length recorded, because the handle on a centre pivot sits at the top of the sash and the handle on a top hung unit sits at the bottom. Those two positions can differ by nearly a metre on a long unit and they change the answer.

2.3m
3.5m
2.4m
40°

Centre pivot and top hung: two different meanings of the word opening

Sealed unit, seated on the frame and never on the covering.
Insulated kerb, 150mm from the finished surface to its top edge.
Covering dressed up the kerb face and closed under the frame.
Deck and roof structure. The kerb is fixed to this, not to the deck alone.

A centre pivot sash rotates about a horizontal axis roughly halfway up the frame. The bottom swings in as the top swings out, so part of the sash comes into the room. It gives good through ventilation, it rotates right round for cleaning from inside, and it is the cheaper and more common arrangement. The catch is the sash intruding into the room at head height, which matters if there is a desk, a bed or a landing directly under it.

A top hung sash is hinged at the head and swings outward and upward from the bottom, like a hopper in reverse. Nothing comes into the room, the view out is unobstructed because you can lean into the opening, and the clear openable area is larger for the same frame size. Top hung units usually cost more, and the sash at full extension is a substantial sail in wind, which is why the wind and sensor behaviour further down this page matters more on a top hung unit than on a pivot.

Both are available with electric operation. Manufactured roof windows from VELUX, Fakro, Keylite and Roto all offer electric variants of their standard sizes, so an electric unit is not a special order in the way a made-to-size flat roof rooflight is. Sizes and codes for the manual versions are on the roof window installation and VELUX window installation pages.

What is actually inside the top of the sash

On a manufactured electric roof window the mechanism is a chain actuator: a small geared motor driving a rigid link chain that pushes out of a housing concealed in the head of the sash. The chain is stiff in compression along its own axis and flexible the other way, so it can be coiled inside a shallow box and still push a heavy sash open. Typical stroke lengths give an opening angle of around 15 to 25 degrees on a top hung sash, which is plenty for ventilation and nowhere near enough for escape.

The housing adds depth to the top rail. On a standard roof window that depth is designed in and you would struggle to tell an electric unit from a manual one at a glance. On a slim cast conservation frame there is far less room to hide it, and the actuator ends up as a visible box on the inboard face. That is generally acceptable because the outside of the roof stays flush, which is what a conservation officer is looking at, but it is worth seeing a photograph before the order goes in. The frames themselves are covered on the conservation rooflight installation page.

Electric units also carry a motorised locking bar or a driven latch, because a sash that is pushed shut by a chain and held only by gaskets will not stay weathertight. The lock drives home after the chain has closed the sash fully, and if the closing cycle meets resistance the whole thing reverses rather than forcing.

Spindle and ram actuators on kerb mounted units

A made-to-size opening rooflight on a flat roof works differently. The sash is a full glass pane in a slim aluminium frame, hinged at one edge on the kerb, and it is driven by one or two spindle actuators: a threaded rod that extends out of a tube as the motor turns it. Two actuators are used on wider units so the sash lifts evenly and does not rack across its diagonal.

The stroke is longer than a chain gives, commonly 300 to 400mm of clear lift at the leading edge, and because the unit is nearly horizontal that translates into a genuinely large ventilation opening. There are also short stroke versions sold as ventilation flaps, lifting perhaps 150 to 200mm, which are cheaper, quieter and adequate where the point is background air rather than purge.

The actuator has to live somewhere. On a kerb mounted unit it sits inside the upstand, below the glass line, which means the kerb has to be built deep enough to house it and the insulation on the outer face of the kerb has to work around it without leaving a cold gap. A cable also has to reach it, through the kerb, before the waterproofing goes on. Get that sequence wrong and the alternative is a cable surface run across a finished single-ply membrane, which is exactly the sort of afterthought that shows. Kerb construction and falls are set out on the flat roof rooflight installation page.

Mains electric, solar, or a rod on a manual unit

Daylight from above falling across an interior wall

Three specifications cover almost every situation, and they are chosen against reach, against whether the room is finished, and against what the building will let you do with a cable.

A mains electric unit is the strongest and the most capable. It opens fast, it closes hard against its gaskets, it drives a locking bar, it runs a rain sensor continuously without worrying about charge, and it will operate an electric blind from the same supply. It needs a cable.

A solar unit carries a small photovoltaic panel on the outside of the top rail, a rechargeable battery inside the sash, and the same chain actuator and rain sensor as the mains version. It needs no cable at all, which is the entire point. In a finished loft room with plastered slopes, or in a listed roof where a chased cable run would need consent of its own, the solar option turns a disruptive job into a straightforward one.

A manual unit with a telescopic rod is the right answer more often than people expect. It costs a fraction of the electric version, there is no motor to keep working, and where the handle is at 2.6 metres rather than four, a rod hooked over the bar does the job perfectly well. The rod lives in a cupboard and gets used because it is easy. What it will not do is close the window when it rains while you are out.

Solar openers, battery life, and the slopes where they struggle

Solar performance is about daylight, not direct sun. The panel is a few watts and the actuator only draws current for the twenty seconds or so it is running, so the energy budget is small. On a south, east or west facing slope anywhere in the county a solar unit will hold charge through winter without difficulty.

North facing slopes are where it gets marginal, and Gloucestershire has two situations that make it worse. A north facing rear slope in a Stroud valley terrace can sit in the shadow of the hillside opposite for most of a December day, and the vale gets long runs of flat grey weather in which nothing charges quickly. In those positions a solar unit still works, but it charges slowly enough that heavy use in midwinter can run the battery down, and the unit then sits closed until it recovers. Overhanging trees and a dormer cheek that shades the panel do the same thing.

The battery is a consumable. Expect something in the region of ten years before it holds noticeably less than it did, and it is replaceable from inside without touching the roof. That is a far better position than a failed mains cable buried in a plastered reveal.

Running the cable: the route, the entry point and the vapour layer

On a mains unit the cable enters at the head of the sash, so it has to arrive at the top corner of the frame, inside the construction, before the reveal is boarded. The route runs from the power supply position, along the side of a rafter, clipped to the timber and kept out of the 25mm ventilation gap above the insulation, then through a grommeted hole in the frame liner.

The detail that gets skipped is the vapour control layer. Every cable that crosses it is a hole in it, and warm humid air pushed through that hole into a cold roof void condenses on the underside of the sarking. A proper job uses a purpose made grommet or a taped collar, and the tape is a vapour tape rather than gaffer. This is exactly the same principle as the reveal insulation detail described on the home page, and it fails in the same way: a damp mark in the top corner of the plaster in February, months after everybody has forgotten the cable.

Cable is run before plaster. Where a room is already finished and the customer wants mains rather than solar, the choices are lifting a section of plasterboard at the head of the opening, running the cable in the loft void above a flat ceiling section and dropping it in, or a surface run in slim trunking. All three get priced honestly at survey with photographs, because the third one is visible for the life of the room.

The 230V side of it, and the certificate that comes with it

Depending on the range, a mains opening unit either takes a 230V supply directly to a connection at the head of the window, with the low voltage electronics inside the sash, or takes low voltage from a control unit sited in the loft that is itself fed at 230V. The second arrangement puts the transformer somewhere accessible, which is worth insisting on, because a power supply buried above a plasterboard ceiling with no hatch is a problem waiting for its moment.

The 230V connection is a fused supply from a suitable circuit, either a spur from a socket circuit through a switched fused connection unit, or its own way in the consumer unit where several units and blinds are being fed. It is notifiable work under the electrical part of the Building Regulations, it is tested and certified, and the certificate forms part of the paperwork handed over at the end of the job alongside the Building Control completion certificate.

Two practical points. Site the isolation switch where somebody can find it, not in the eaves. And keep the supply for the rooflights off the lighting circuit in a loft room, because an opening unit that stops working every time a bulb blows a circuit is an irritation that lasts for years.

A roof window seen from inside a room in the roof

Rain sensors, and the things that set them off when it is not raining

The sensor is a small pad on the outside of the sash, usually at the top, with two conductive tracks a millimetre or two apart. Water bridging the tracks drops the resistance between them, the electronics see the change, and the unit closes. Response is a few seconds from the first drops, which is fast enough that on a normal shower you get a splash on the reveal and nothing on the floor.

It is not selective about where the water comes from. Heavy morning dew triggers it. So does a garden sprinkler, a hose on a car, a window cleaner working on the elevation, and in the vale, a thick autumn river fog that condenses on everything. On roofs under trees the pad collects leaf debris and moss spores, and a sensor with a mat of green growth across it can either stay permanently wet or stop reading altogether, which is why cleaning it is on the short maintenance list at the end of this page.

There is usually an override. Holding the open button reopens the unit for a set period even with the sensor wet, which is useful when you are standing in the room and can see the shower has passed. What you cannot do is override it and go out, which is the correct behaviour for a hole in a roof.

Wind, obstruction detection and the sash as a sail

A top hung sash open to 20 degrees on an exposed roof presents a real area to the wind. The forces are handled in three ways. The actuator itself has a rated holding force and is self locking under load, so wind cannot drive the chain back in. The sash and hinges are designed for the load. And the sensible operating habit is to close the unit before a front arrives, which is a manual decision on most units because a rain sensor reads water rather than wind.

Exposure varies more across this county than people assume. The Cotswold escarpment above Cheltenham and the ridge running from Birdlip to Painswick take the full south westerly with nothing in front of them, and a roof at 250 metres on the wolds gets weather that a sheltered Gloucester terrace never sees. The Forest is wetter and windier again. On those positions the specification leans towards a shorter opening stroke and a top hung sash sized modestly rather than a large unit opened wide.

Obstruction detection matters inside. The motor monitors current draw, and a rise beyond the expected profile means something is in the way, so the drive stops and reverses. It works reliably on a hand or a blind cord. It works less reliably on something soft and yielding, so a bed pushed under a centre pivot unit is still a bad idea.

Controls: wall pad, handheld remote, and the one that gets lost

A flush glazed rooflight set into a flat roof

Most systems ship with a handheld remote and offer a wall mounted control as an option, and the useful arrangement is both. The wall pad goes in a fixed sensible position, usually at switch height by the door of the room or at the head of the stairs, and it is the control that anybody unfamiliar with the house will find. The handheld is the one used in practice by the people who live there.

A wall pad may be wireless, battery powered and simply stuck or screwed to the plaster, or it may be a wired control on a cable back to the unit. Wireless is far easier to fit and it can be moved. Wired is worth having where the pad also needs to be dependable for a room used by an elderly resident, and where the cable can be run at first fix anyway.

Handhelds get lost. Every system allows a replacement to be paired, and every system has a slightly different pairing sequence involving a recessed button on the unit or a sequence of presses on an existing remote. That is exactly the information that vanishes when a homeowner moves house, so the model numbers and the pairing method go in the handover pack rather than being left in an instruction leaflet on top of a wardrobe.

Radio protocols, gateways, and controlling a rooflight from a phone

Manufacturers use different radio systems and they do not talk to each other. VELUX electric and solar units use io-homecontrol, a two way protocol shared with Somfy, which means the window reports its state back to the control rather than just receiving commands. Fakro’s electric range uses Z-Wave, which is an open home automation standard with a large ecosystem behind it. Keylite and Roto have their own arrangements. Mixing brands on one roof means two remotes, which is fine, but it is better decided deliberately than discovered.

Phone control needs a gateway: a small mains powered box on the house network that translates between the radio protocol and the internet. Once that is in, the unit can be opened from a phone, put on a schedule, and in some systems driven by indoor air quality readings so the window opens when carbon dioxide or humidity climbs. That last one is genuinely useful in a loft bedroom with a door that stays shut all night.

Be realistic about what a gateway adds and what it costs you. It depends on a router, a cloud service and an app, all of which change over time, and none of which are needed for the window to work from its own remote. Specify the gateway if you want scheduling, and treat it as an addition to a system that already functions without it.

Escape windows: an opener is never the only way out

Where a roof window forms the means of escape from a loft room, it has to be openable by hand, by an occupant, in the dark, with no power. That is the whole point of it. An electric actuator can be fitted to an escape window, and the manufacturers make units that combine the two, but the manual escape function is the primary duty and the motor is an addition to it.

The dimensional requirements are specific. The clear openable area must be at least 0.33 square metres with a minimum of 450mm in both height and width, and the bottom of the openable area between 800 and 1100mm above the finished floor. Fire service guidance also expects the window to be reachable from outside, which in practice means within about 1.7 metres of the eaves measured along the slope. An escape unit is therefore top hung, opens to a wide angle, often 45 degrees or more, and has a manual handle regardless of what else is fitted.

The common and expensive mistake is a fixed or standard electric unit specified in the escape position because it looked right on the drawing, discovered at the Building Control inspection when the room is decorated. It gets caught at survey here, because the escape window position on a loft conversion is checked before anything is ordered.

450mm
1100mm
1.7m
45°

Purge ventilation arithmetic, and the one twentieth figure

Purge ventilation to a habitable room means being able to open something with a clear area of at least one twentieth of the floor area of that room. A 12 square metre loft bedroom therefore needs 0.6 square metres of openable area, and that is where the difference between a chain actuator and a wide manual opening starts to matter.

An electric unit opening to 20 degrees does not give its full frame area as clear opening. The geometry is roughly the frame width multiplied by the perpendicular gap created at the free edge, and on a top hung sash opened 20 degrees that gap is a fraction of the sash length. A 1140 by 1180mm unit opened to 20 degrees gives something in the region of 0.4 square metres of clear area rather than the 1.3 square metres of glass. Two units, or one unit plus an openable window in a gable, gets there. One electric roof window on its own in a large room often does not.

Trickle or background ventilation is a separate requirement met by a vent flap in the head of the frame, which most manufactured roof windows include and which works with the sash closed and locked. It is the one most often shut by occupants who think it is a draught. It is not: it is the thing keeping the room from misting up.

20°
1180mm

Passive stack through a stairwell, using high and low openings together

An opening rooflight at the top of a stairwell is the most effective single ventilation device in most houses, and it works on the stack effect rather than on wind. Warm air is less dense, so it rises up the stairwell and out of the high opening, and that outflow pulls cooler air in through anything open at the bottom of the house. The taller the house the stronger the effect, which is why it works so well in the three storey terraces cut into the Stroud valleys and in Cheltenham’s tall town houses.

The arithmetic that matters is the pairing. A high opening on its own vents slowly because air cannot get in to replace what leaves. Open a ground floor window as well and the flow rate rises sharply. Practically, that means the rooflight over the stair is the one you leave open on a summer night with a window ajar downstairs, and it will drop the temperature of a top floor bedroom by several degrees before morning.

Which brings the reach problem back. A rooflight over a stairwell is unreachable by definition, so it is either electric with a rain sensor or it is a unit nobody ever opens. That single position accounts for a large share of the electric units fitted in the county.

Summer overheating on a south west facing conversion

A loft room under a south or west facing slope in Gloucestershire gets uncomfortable in July, and the glass overhead is the reason. Sun at a high angle strikes a 40 degree south facing roof close to perpendicular, so the solar gain per square metre through a roof window is far higher than through a vertical window in the same wall.

Opening the window helps at night and hardly at all in the middle of the day, because at that point you are letting hot outside air into a room that is already hot. The order of effectiveness is: keep the heat out with a solar control coating on the outer pane, shade the glass on the outside with an external awning blind, shade it on the inside with a blackout blind, and purge at night with the sash open. An external blind is dramatically more effective than an internal one because it stops the energy before it reaches the glass, and on an electric unit it can be driven from the same control system.

Approved Document O sets an overheating standard for new dwellings and does not bite on a loft conversion in an existing house, but the physics is identical and it is worth designing against. Glass specifications and the numbers behind them are on the energy efficient rooflights page.

Smoke ventilation is a different product with a different certificate

An automatic opening vent, an AOV, looks like an electric rooflight and is not one. It is a life safety device: certified to the smoke and heat control standard, driven by a dedicated control panel with its own battery backup so it works in a fire when the power has gone, wired in fire rated cable, triggered by a smoke detector or a break glass unit, and required to achieve a stated free area rather than a comfort ventilation figure. Common stairwell requirements run to one square metre of aerodynamic free area.

The distinction matters because a fire strategy for a converted building, or for flats sharing a stair, will call for an AOV in a specific position, and a comfort electric rooflight in that position does not satisfy it. Neither does an electric rooflight with a smoke detector wired to it. If a drawing shows an AOV, the product ordered is an AOV.

Where a specification is unclear, the person to ask is whoever produced the fire strategy or the Building Control body, before an order is placed. It is a five minute question at design stage and an expensive one after the ceiling has gone in.

Electric blinds, and why they are ordered with the unit

Blinds for roof windows run in guide channels formed into the sides of the sash, and those channels are part of the frame. Retrofitting a blind to an existing unit is straightforward when the unit is a current model and its blind range still exists. It is much less straightforward on a twenty year old sash whose channel profile has been superseded, which is one of several reasons a replacement is a good moment to think about blinds.

The electric versions come in three types worth knowing apart. An internal blackout blind in a cassette gives darkness for a bedroom and modest heat control. An internal pleated or venetian blind diffuses light and does very little for heat. An external awning blind is a mesh screen that runs down the outside of the glass, cuts solar gain substantially before it reaches the pane, and can be left down in rain.

Order blinds with the window. A mains electric unit can feed a mains blind from the same supply and pair it to the same remote, so one wall pad drives both. Deciding on a blind after the reveal is plastered means either a solar or battery blind, or a second cable, and the second cable is the expensive one.

Operation types compared against reach, power and what each one needs

Operation	Practical reach limit	Power required	Rain sensor	Best suited to
Manual, handle at the sash	Frame head up to about 2.3m above floor	None	No	Bedrooms and rear additions where the unit is within arm’s reach
Manual with telescopic rod	About 3.3 to 3.5m	None	No	Loft rooms with a high frame head and a floor directly underneath
Solar electric, chain actuator	No practical limit	Photovoltaic panel and internal battery	Yes	Finished rooms, listed roofs, anywhere a cable route would cause damage
Mains electric, chain actuator	No practical limit	230V supply, notifiable and certified	Yes	New openings at first fix, multiple units, anywhere a blind shares the supply
Mains electric, spindle actuator on a kerb	No practical limit	230V, cable run through the kerb before waterproofing	Yes	Flat roof rooflights over kitchens and single storey rear extensions
Manual escape window, wide opening	Handle within reach by requirement	None, motor optional as an addition	Only if electric is added	The designated escape position in a loft conversion
Certified automatic opening vent	Not applicable	Dedicated panel, battery backup, fire rated cable	No, smoke triggered	Stairwells where a fire strategy calls for smoke ventilation

Opening geometry against the clear area you actually get

The number that satisfies a ventilation calculation is clear openable area, not glass area, and the two are a long way apart on an electrically opened unit. The table gives the working relationship for common arrangements. Treat the figures as indicative for specification discussions and confirm against the manufacturer’s data for the exact size chosen.

Arrangement	Typical opening angle or stroke	Clear area as a share of frame area	What limits it
Top hung, chain actuator	15 to 25 degrees	Roughly a quarter to a third	Actuator stroke length, fixed by the model
Top hung, manual, escape rated	45 degrees and beyond	Close to the full frame area	Hinge design and the stay
Centre pivot, chain actuator	Around 20 degrees	Roughly a fifth to a quarter, split above and below the pivot	The sash intrudes into the room, so the angle is kept modest
Centre pivot, manual	Up to 45 degrees on the catch	Around a third, in two gaps	Room intrusion at head height
Kerb mounted opening rooflight, spindle	300 to 400mm of lift	Substantial, often over half	Kerb depth, actuator housing, and glass weight
Kerb mounted ventilation flap	150 to 200mm of lift	Modest, background rather than purge	Deliberately short stroke
Vent flap in the frame head, sash closed	Not applicable	Background ventilation only	Free area of the flap grille

Cotswold stone slate, and an actuated unit that still has to sit low

On the wolds roofs through Painswick, Bibury, Northleach and Chipping Campden the covering is graded stone slate laid in diminishing courses, thick, heavy and torched from below with lime mortar. Any opening means taking the courses back up the slope and re-laying them to the original gauge with matched reclaimed slates, so the unit going in is chosen for how low it sits rather than for its feature list.

That constrains electric operation in a specific way. A slim cast conservation frame has very little depth in the top rail to hide a chain actuator, so the mechanism sits proud on the inside face. Some manufacturers offer a factory electric version with the housing designed in; others leave you fitting a surface mounted actuator to a manual sash. Both keep the outside flush, which is the part a conservation officer cares about, and the internal box is usually invisible from the room below because it faces up the slope.

The other reality is that these are old, cold, high roofs in villages where the top of a first floor slope can be four metres above the floor of the room. A rod is not the answer in a cottage bedroom with a beam across it. Solar is often the right specification precisely because there is no cable run through a lime plastered slope to argue about with the conservation officer.

Cheltenham stairwells, listed roofs, and cable you cannot conceal

Central Cheltenham’s town houses have tall stairwells rising three or four storeys to a shallow slate roof or a lead flat behind a parapet, and a rooflight over that stair is frequently the only daylight the middle of the plan gets. It is also completely unreachable, so electric operation is the default rather than an upgrade.

The complication is the fabric. Many of these buildings are listed, and on a listed building consent covers work nobody outside will ever see, which includes chasing a cable into original lath and lime plaster or drilling through historic joinery. A solar unit sidesteps the whole conversation. Where mains is genuinely wanted, for instance because an external awning blind is going on the same unit, the cable route is agreed in advance and run in the roof void or in a slim surface trunking that can be removed, rather than buried.

There is also the physical business of getting to it. A four storey stairwell has no floor to stand on. Access for the internal side of the work is by a proprietary stair tower or a scaffold built inside the stairwell, and that is priced from the survey rather than guessed at, because it is often the largest single item on a job of this kind.

Trussed roofs at Quedgeley and Bishops Cleeve, and where a cable may cross

On the trussed estates around Quedgeley, Abbeydale, Brockworth, Bishops Cleeve, Ashchurch and Yate the roof is factory made triangulated frames at 600mm centres held with punched nail plates. The webs and chords stay whole, and an opening either fits between two trusses or needs a designed trimmer with the affected truss carried off it.

Cable routing has its own version of that rule. A hole drilled through a truss member is a notch in a designed structural element, and the nail plate zones are the worst place to do it. The route therefore runs on the face of the members, clipped to the side of a chord and taken across the roof rather than through it, or it runs in the ceiling void below the bottom chord where there is usually plenty of room. Where a cable must cross a member, it crosses in the middle third of a bottom chord, in the smallest hole that will pass the cable, and never through a plate.

The compensation on these estates is that everything else is easy. Access is a driveway, the covering is concrete interlocking tile that unclips and re-lays, and a 550 by 980mm unit drops between two trusses with a head and cill trimmer and nothing more. A pair of electric units in adjacent bays on a rear slope is one of the most straightforward jobs available in the county.

Steep Forest of Dean slopes, and the handle above the reach line

Around Coleford, Cinderford, Mitcheldean and Lydney the houses are local sandstone with Welsh slate at 40 to 45 degrees, often over sarking boards, in former mining terraces with thick walls and small rooms. The steep pitch does something specific to reach: for a given height up the slope, the frame head is further above the floor than it would be on a 30 degree roof, and the reveal becomes a taller box that puts the sash further away again.

Work it through on a typical Forest first floor bedroom. A 45 degree slope, a unit set 1.5 metres up the slope from the eaves, and a 400mm deep reveal at the head puts the handle comfortably beyond 2.6 metres. That is above the comfortable manual line and into rod or electric territory, and on a centre pivot with the handle at the top of a 1400mm sash it is worse still.

The weather adds a second argument. The Forest takes driving rain from the south west with force behind it, more of it and more often than the vale, so head laps get increased over the manufacturer’s minimum and side flashings taken wider. In that exposure a rain sensor is doing real work: an open unit and a squall arriving over the ridge is a common combination, and the unit closes itself while nobody is home.

45°
30°
1.5m
400mm

Stroud valley gables, and lifting an actuated unit into position

Stroud, Chalford, Rodborough, Thrupp and Nailsworth are built into the sides of the valleys, so terraces step up the hill and a cottage is one storey at the front and three at the back. Access is by shared lane, footpath or a flight of steps, retaining walls sit hard against the elevation, and there is often nowhere flat to stand a tower.

An electric unit is heavier than its manual equivalent, and a made-to-size opening rooflight with two spindle actuators and a large glass pane is heavier again. Where a lorry cannot get within fifty metres and scaffold has to be hand carried in, that weight is not a detail. It means more hands on the day, sometimes a mechanical lift, and a longer programme. It is priced from the survey with the access looked at properly, because a figure that ignores the lane does not survive the first morning.

The payoff is real. A cottage cut into a bank with a retaining wall behind it and neighbours tight on both sides has no elevation left to put a window in, and daylight from overhead is the only daylight available. Because the top of a three storey rear elevation is a long way above the floor inside, these are also the houses where an opener is not a luxury.

Interwar landings and hipped rear slopes across Longlevens and Hucclecote

The interwar and post war semis through Longlevens, Hucclecote, Tuffley, Warden Hill and Charlton Kings are hipped concrete tile at 30 to 35 degrees over a cut roof with purlins and struts. The rafters can be trimmed, which makes them easy roofs to work on, but a hip narrows the slope towards the corner and a purlin crosses at about mid height, so the clear zone is often only around 1.2 metres of vertical run across two bays.

The position that most often wants an opener in these houses is not the bedroom, it is the landing. A small unit over the stair well between the ground and first floor lands three to four metres above the treads, throws light down into a hall that has none, and vents the whole house through the stack effect on a summer night. It cannot be reached, so it is electric or it is decorative.

The good answer on the rear hip remains two units in adjacent rafter bays rather than one wide one: no structural design needed, more glass in total, and more even light. If those two are electric they pair to one remote and open together, which is a better result in a bedroom than a single large sash on one side of the room.

Adding electric operation to a unit that is already in the roof

Some manual units can be motorised in place and some cannot, and the answer depends on the model rather than on effort. Current generation manufactured roof windows often have a retrofit actuator kit designed for them, sometimes solar so that no cable is needed, which clips into the top rail and pairs to a remote. Where that kit exists it is a short job from inside, with no scaffold and nothing touched on the roof.

Older sashes are a different matter. A twenty year old frame may predate the actuator mounting arrangement entirely, its gaskets are likely at the end of their service life, and hanging a motor on a sash that is already tired buys very little. At that point the sensible comparison is a retrofit kit against a new complete unit that arrives with the actuator, the sensor, the locking bar, current glass and a matching blind channel. Where the frame is past twenty years the second option is usually better value than it looks, and the wider replacement question is covered on the skylight replacement page.

The survey answers this by reading the size and model code stamped on the sash, which on most roof windows is on a plate at the top of the frame visible when the sash is rotated. Send a photograph of that plate with an enquiry and the answer comes back the same week.

Handover: what gets demonstrated before the scaffold comes down

An electric installation has a commissioning stage that a fixed unit does not. The sash is cycled fully open and fully closed several times to confirm the stroke is correct and the locking bar drives home. The rain sensor is tested with water, actually wetted rather than assumed, and the closing cycle timed. The override is demonstrated. The wall pad and every handheld are paired and each one is operated in front of the customer.

Where a blind is fitted, it is cycled and its limits set, because a blind that stops 40mm short of the bottom of the glass in a bedroom is a complaint that arrives in the second week. Where a gateway is specified, it is connected, the app is set up on the customer’s own phone and one schedule is created so the mechanism is understood rather than described.

The paperwork handed over is the Building Control completion certificate, the electrical certificate for the 230V work, the manufacturer’s warranty documents for the unit and its motor, the model and size codes, the pairing instructions, and a note of where the power supply and the isolator are. The workmanship carries a ten-year guarantee, written against the perimeter details that the workmanship controls: upstand height, falls, flashing laps and fixing pattern, and how the underlay is dressed around the frame.

Keeping an electric unit working: chain, gaskets, sensor, battery

There is very little to do and it is worth doing. Twice a year, wipe the rain sensor pad clear of debris and any moss growth, because a permanently wet pad means a unit that will not open and a dead pad means one that will not close in a shower. On a solar unit, clean the photovoltaic panel at the same time; a film of algae on a north slope costs real charging capacity.

Once a year, look at the gaskets around the sash with the unit open. They are the seal that the motor drives the sash against, and a perished gasket shows up as a draught, a whistle in wind or a line of daylight at the edge of a closed unit. Wipe the drainage channel in the bottom of the frame clear, because that channel is what carries away the water that always crosses the covering, and blocked channels put water where the design never intended it.

The chain wants a wipe and nothing more; the lubrication in it is factory applied and adding oil attracts dust. Handheld remote batteries last a couple of years. A solar unit’s internal battery has a service life measured in years rather than decades and is replaced from inside. Where an actuator itself reaches the end of its life, it is a replaceable component on most current ranges, not a reason to take the window out.

What moves the figure on an electrically operated job

An electric unit costs more than the manual version of the same size, and on most jobs that difference is smaller than the things around it. What genuinely drives the number:

Solar against mains, because solar removes the cable route and the certified electrical work entirely.
Whether the room is finished. A cable at first fix is trivial; a cable into a plastered and decorated reveal is carpentry, plastering and decoration.
How far the 230V supply has to come, and whether it is a spur or a new way in the consumer unit.
The roof covering, from concrete interlocking tile at the straightforward end to Cotswold stone slate in diminishing courses with matched reclaimed material at the involved end.
Whether structural work is needed, which is decided by the size wanted against the rafter or truss spacing.
Access, including valley sites, hand carried scaffold, and internal access over a stairwell with no floor to stand on.
Blinds, and whether they are internal, external, mains or solar.
Number of units, because one scaffold, one notification and one visit spread across three units is materially cheaper than three separate jobs.

Then two figures, in this order. An indicative range by email first, from photographs of the roof and the room, the covering, a rough size and the address. Then a fixed price after a survey, itemised so it is clear what is unit, what is labour, what is scaffold, what is electrical and what is Building Control. The costs page sets out how that process runs.

How to start, and the four things that make the first reply useful

Email info@severnskylightsgloucester.co.uk with a photograph of the roof from the garden or the street, a photograph of the room from inside, a rough measurement from the floor to where you think the frame head will sit, and a note of whether there is a power source anywhere near. Those four things are enough to say whether solar or mains is the sensible route and whether the position is reachable manually.

An address helps more than people expect, because on a Gloucestershire roof the covering, the exposure and the conservation status are often obvious from the postcode. Coverage town by town is on the areas pages, individual questions are answered in the written guides, and about explains how the company works. Openable options for other unit types sit on the roof lantern, walk-on rooflight and sun tunnel pages.

A rooflight nobody can reach is a rooflight nobody opens, and a closed rooflight ventilates nothing.

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