Energy-efficient rooflights for Stockport homes

Energy-efficient rooflights in Stockport

Rooflights compared on the whole-unit figure, so the glass, the frame and the kerb are judged together.

Fixed written quote
We handle the Building Regulations notification where the work is notifiable
10-year workmanship guarantee

Close-up of a flat glass rooflight on a wet flat roof

An energy-efficient rooflight lets daylight into a room while holding on to the warmth you have paid for. In practice that means a well-insulated frame, a glass unit chosen for the room it serves and a kerb or surround that does not leak heat round the edges. Roof windows, flat rooflights and lanterns all come into it, whether the job is a new opening or the swap of an existing unit, for homes within reach of Stockport.

A photo cannot price a rooflight, so a free survey opens the job and the fixed written quote is drawn from it, while the guarantee we give on the fitting runs for ten years on workmanship and is written down. For the full picture of what we install, see installing and replacing skylights and rooflights across Stockport.

A man holding a sample of triple glazing at his kitchen table

Blinds, vents and cleaning for efficient glass

Blinds are made to suit the unit's maker and size code. A bedroom takes blackout, a kitchen a softer weave and a bathroom a fabric built for steam.
Some rooflights have an opening vent, worked by pole, switch or remote, which clears damp air from a kitchen or bathroom.
A water-fed pole standing on the ground, or a ladder placed at the eaves, reaches the outside of the glass. A dirt-shedding coating is the maker's feature on some glass only.
Where a maker supplies a rain sensor with an electric or solar vent, it shuts the vent as rain begins, and we name the models that include one.

Energy performance of rooflights

Energy-efficient rooflights in Stockport: reading the figures before you choose

U-values, glass, frames, summer heat and condensation, then the survey and what the work involves.

Rooflight datasheets are full of numbers, and they do not all measure the same thing. These chapters go through the figures that matter in England, what each type of glass and frame does for them, and how a room's use shapes the choice.

What makes a rooflight energy efficient, and will it still bring in daylight?

Natural light and daylight, kept in balance

A rooflight is there to bring daylight into a room, and an energy-efficient one must do that without letting heat out in winter or in on a hot afternoon. Those aims pull in different directions. More glass means more daylight and more surface for heat to cross, while a better pane or a better insulated frame lowers the loss per square metre. Good specification balances the two for one particular room.

The Building Regulations in England set no daylight requirement for houses. The amount of glass is therefore a design choice and not a rule, and the first question at survey is what the room is used for.

Centre-pane and whole-unit figures

A datasheet can show two kinds of U-value. A centre-pane figure describes the glass in the middle of the pane. A whole-unit figure also takes in the frame, the spacer round the edge of the glass and the junction with the kerb, so it describes the product as it will sit on your roof. It is the more honest guide, because the edges of a unit lose heat faster than the middle. When a maker quotes a very low number, check which kind it is before setting it beside another product.

Roof windows and rooflights have different yardsticks

A roof window follows the pitch of the roof, while a rooflight sits proud of it on a kerb. Part L gives each its own figure, which the Part L chapter sets out, and by Approved Document L's definition a lantern is a rooflight too. Someone asking for a skylight could mean either, so the first question at a survey is about the shape of the roof.

Daylight and how a room feels

Rooms lit from above can feel bigger and calmer than the same room lit from one wall: brightness on the table, the stairs or the worktop, without a lamp. Efficiency figures protect that gain, because a room that is comfortable in winter is a room you want to sit in.

Insulation round the edges

The best glass is let down by a cold edge. Insulated kerbs, thermal breaks in aluminium frames and a well-sealed junction with the roof covering all matter, and a datasheet that quotes only the glass leaves them out. We ask the maker for the whole-unit figure before recommending a unit.

Reading a datasheet

Centre-pane U-value: The glass alone, measured in the middle of the pane
Whole-unit U-value: Glass, frame, spacer and edge taken together
Window Energy Rating: A banded grade for a roof window as a whole
Light transmission: How much daylight passes through the glass
Solar factor: How much of the sun's heat passes through

Which rooms in my home gain most from an efficient rooflight?

Loft, bedroom and study

A loft conversion is where a pitched-roof window earns its figures, since the glass forms part of the room's outer envelope. A loft bedroom wants blackout, a study wants softer light, and both want a frame that does not run cold at the edge. A roof window with a good whole-unit figure and a blind bought for it is a sensible pairing. Our roof windows page covers the pitched-roof side.

A loft study with a timber roof window, bookshelves and a radiator

Kitchen, dining room and bathroom

Kitchens and bathrooms add moisture, and glass that stays warm on the inside gives that moisture less to settle on. A kitchen or dining room extension with a flat roof has room overhead for a lantern or flat glazing on a kerb, while an orangery-style extension can be designed round one. A bathroom below a flat roof can have a small rooflight with a damp-room blind.

Homes around Stockport

The houses vary a good deal, and homes come first for us, while small commercial work, a shop back room or a small office say, is welcome too.

Victorian terrace in Edgeley: may have a back addition that stands in its own shadow.
Villa in Davenport: may have an attic with room for a generous pitched window.
Bungalow in Heald Green: may lose its light from a rear extension.
Marple stone house: may need a roof window chosen to sit well in its roof covering.

In each case the efficiency figure has to fit the room first.

Where an efficient rooflight is the wrong answer

A very large glazed area on a south-facing roof can overheat a room whatever the U-value. If the survey suggests a smaller opening or a sun tunnel, which is a light tube from the roof to a ceiling diffuser, we say so.

What do the Building Regulations ask of a rooflight's energy performance?

The two figures

In England, a new or replacement roof window in an existing home should have a U-value no worse than 1.4 W/m²K, or a Window Energy Rating of Band B or better. A rooflight on a kerb is held to a different figure: a U-value no worse than 2.2 W/m²K. Of the pair, 1.4 belongs to a window in the plane of the roof and 2.2 to a unit on a kerb, and the two should not be swapped. Our rooflight U-values and Part L page works through the detail.

The whole outer surface and the kerb

A rooflight's U-value is based on its whole outer developed surface area, which is often larger than the hole in the roof. Where the kerb comes as one assembly from the same supplier, the 2.2 limit covers the kerb too; an upstand built on site should be no worse than 0.35 W/m²K. That is why we ask whether a kerb is supplied with the rooflight or built on the roof before comparing two quotes.

Replacing a unit, and replacing only its glass

Before anything is measured, we read the label fixed to the unit as it stands today. A replacement element should also be no worse than the one it replaces. Reading the old label shows what that is. Replacing only the glass, or a window in its existing frame, is not providing a controlled fitting, so the energy limits do not apply to that work. Taking out the whole unit, frame included, and fitting another is a controlled fitting, and the limits apply.

Glazing area in Approved Document L

Approved Document L offers a whole-home guide, and it applies when a window or roof window is enlarged or a new one is created: the total area of windows, roof windows, rooflights and doors should not exceed 25% of the home's total floor area, unless compensating energy-efficiency measures are taken. Before an opening is made bigger, a survey adds up the glass across the home.

Notification to the council

Where the work is notifiable, we handle the Building Regulations notification with the council's building control team or a registered building control approver. Detail on what counts as notifiable work sits in the Building Regulations guide.

The England figures side by side
Product	Figure	Measured over	Note
Roof window	WER Band B, or 1.4 W/m²K	The whole window	Follows the roof pitch
Rooflight	2.2 W/m²K	Whole outer surface	Sits on a kerb or upstand
Kerb supplied with the unit	Inside the 2.2	Part of the assembly	One supplier
Upstand built on site	No worse than 0.35 W/m²K	The upstand	Insulated on the roof

Double or triple glazing, aluminium or uPVC: which choices change the numbers?

Double glazing and its coatings

A double-glazed unit is two panes with a sealed gap between them. On one pane there can be a low-emissivity coating, a thin layer that sends warmth back toward the room, and some makers fill the gap with gas. Both are specification choices, so they should be listed for the unit, not assumed. A manufacturer range will list the glass options available for each rooflight or roof window.

Triple glazing

Triple glazing adds a third pane and a second gap. It lowers the U-value of the glass further, and the inner pane stays warmer, which gives condensation less to form on. It also makes the unit heavier, so the frame and the structure round it have to suit. Whether it is worth having turns on the room, its exposure and the frame, and our triple-glazed rooflights page weighs it up.

Frames: aluminium, uPVC and timber

Aluminium: some makers build a thermal break into the frame, an insulating strip inside the profile that cuts the cold conducted through the metal.
uPVC: made by some makers for roof windows and rooflights.
Timber: suits older houses, and is painted or lacquered.

Each has a different finish and sightline, and a different look from the room.

Plastic glazing and fire limits

Polycarbonate and GRP are plastic glazing materials and belong to a different class of product. Rooflights near boundaries and plastic rooflights have fire-performance limits; we check these at survey.

Watertight at the edges

Efficiency and weatherproofing meet at the joint with the roof. A frame that is well insulated and badly sealed will leak, and one that is well sealed with no insulation will be cold. The flashing, the kerb covering and the seal round the glass are chosen together, and the unit is fitted as the maker designed it to be fitted.

Made to measure, or from a range

Rooflights for homes can be bespoke, with the maker building the unit to the measured size of the kerb or opening. A roof window usually comes from a set range of sizes, with VELUX the best known of several brands. The survey records the dimensions so the right size is chosen.

Will an efficient rooflight make the room too warm in summer?

Heat coming in

Insulation works both ways, and a very well-insulated room under a big sheet of glass can hold the heat that arrives on a sunny day. The sun's heat enters through the glass and has nowhere quick to go. The risk is greatest on a large unit facing the sun, over a room with few other openings.

Keeping a sunlit room cooler

Solar control glass carries a coating, or a tint, that bounces some solar heat back out before it gets through. It can also cut the light a little or add a tint, which matters in a room that is already dim. Makers differ on which models have it, so it is a feature to confirm, not to assume. Our solar control glass for rooflights page covers the trade-offs.

Blinds and vents

A blind shades the glass and an opening vent lets warm air go. Blinds sit inside the room, and some makers offer an outside awning-type blind that stops the heat before it reaches the glass. Opening is a daily action: someone has to reach the pole, the switch or the remote, so the control is chosen with the user in mind.

Glare and the room's use

Glare is a comfort question as much as a heat one. A screen in a loft study, a table in a bright kitchen or a cot in a nursery each ask for different shading, and the survey notes which of these the room will have. A blind chosen for the room does more for comfort than a further drop in the U-value.

Roof lantern, flat rooflight or roof window

A roof window set in the shade of a neighbouring gable behaves differently from a flat rooflight in open sun. A lantern has glass on several faces and can catch low sun from more than one side. The survey notes which way the roof faces and what shades it, since that shows whether solar control glass is worth it.

Summer-heat terms

Solar factor: The share of the sun's heat that passes through the glass.
Light transmission: The share of daylight that passes through the glass.
Solar control coating: A maker's layer that turns away part of the sun's heat.
Outside blind: A shade fitted outdoors by some makers, which stops heat at the glass.
Opening vent: A panel in the unit that lets warm air out when opened.

How do efficient rooflights work on flat roofs and extensions?

Flat roof rooflights and their upstands

On a flat roof, the rooflight stands on an upstand, and that lifts the glass clear of the roof covering. The covering is turned up the sides and sealed, which makes the joint watertight, and the upstand is insulated, which keeps the edge warm. If the maker supplies the kerb with the unit, the 2.2 limit covers both. Our flat roof rooflights page goes through the build-up.

Roof lanterns

A roof lantern added to an existing flat roof usually stands well over 150 mm proud of the roof, so it normally falls outside Class C and needs planning permission unless the council confirms otherwise. We check this at survey. Lanterns have a page of their own: roof lanterns.

A sitting room with a sofa and two armchairs under a large flat rooflight

Extensions have their own test

Approved Document L treats an extension separately, and its guide is that when a home is extended, the total area of windows, roof windows, rooflights and doors in the extension should not exceed the sum of two things: 25% of the floor area the extension adds, and the total area of any windows and doors that are gone, or no longer exposed, because the extension was built. A wall of glazed doors and a large rooflight can use up that allowance quickly, which the survey works out.

Planning for an extension

In England, adding a rooflight or roof window to a house is usually permitted development under Class C, so it does not need a planning application, provided it meets the Class C limits and conditions. Extension work is covered in our guide to planning permission, which lists what Class C allows and sets out the side-slope condition in full.

A pitched-roof extension

Not every extension has a flat roof. A pitched-roof extension, such as a lean-to or a gable addition, can take roof windows in the slope, and the roof window figure applies to them. Where a pitched roof covers the main space and a flat roof covers a link, one project can use both a roof window and a flat rooflight.

Sun tunnels as an alternative

Where the geometry will not allow a rooflight, a sun tunnel or sun tube is another route for daylight. We cover those on sun tunnels.

Why does moisture collect on rooflight glass, and what can be done about it?

Where the droplets come from

Cooking, showering, drying clothes and breathing all put moisture into the air. When that air touches a surface colder than it is, the moisture condenses. Glass tends to be the coldest surface in the room, so the first beads of moisture show on a window or a rooflight. A better-insulated unit has a warmer inner pane, so there is less for the moisture to settle on, but no glass is immune if the room is damp enough.

What helps

Remove the moisture where it is made: an extractor over the hob, a fan in the bathroom, a lid on the pan.
Ventilate: a rooflight with an opening vent is a handy way to clear the air.
Leave blinds open for a time: a closed blind sits between the warm room and the cold glass and can trap a layer of damp air on the glass side, so a blind in a steamy room is better left open while the room dries.

Our condensation on rooflights page goes through the checks.

Inside the sealed unit

Moisture between the panes is not condensation of the ordinary kind. It means the seal of the glass unit has gone, which calls for a replacement glass unit or a replacement rooflight; the misted rooflight replacement page explains the options.

Maintenance and aftercare

Looking after one is simple: wipe the frame and the glass when you clean, and clear leaves from the upstand so water drains away from the kerb. Before we leave, the controls, the blinds on offer and cleaning the outer glass are talked through.

First checks for damp glass

Extract fan: Does it run while you cook or shower, and for a while afterwards?
Opening vent: Is it opened for a few minutes each day in a damp room?
Blind: Is it left drawn over wet glass for hours?
Between the panes: Moisture here means the unit has failed

What does the survey cover, and what will I be holding when it is done?

Choices that shift a quote

Efficiency choices are priced after the survey

Book a free survey

The survey comes first. A fixed written quote follows it.

GlazingDouble or triple, with coatings the maker offers for that model.
FrameAluminium with a thermal break, uPVC or timber, and the colour.
Size and shapeLarger or bespoke units take more material and more handling.
Kerb or surroundA supplied insulated kerb, a site-built upstand or a roof window flashing kit.
Opening and blindsA fixed unit, a manual vent or an electric one, and the blinds chosen.
Access and structureHow the roof is reached and what has to be trimmed or strengthened.

Survey first, price second

The survey is free and it comes before any price. We measure the opening or the roof, note the covering and the structure, read the label on any rooflight already fitted, and talk through how the room is used. The recommendation shifts with who opens the vent, how high it sits and who else is at home, such as young children or an older relative. To begin with a picture, send one to WhatsApp 07880 284133; it helps us prepare, though a photo by itself never sets the price.

Comparing energy figures fairly

Ask any installer for the maker, the model, the glass specification and the whole-unit figure, so that two prices can be compared on the same footing. A fixed written quote cannot reflect your roof without the survey, because what shifts it sits in the roof and the room.

Energy choices that shift a quote

Factor by factor, the energy-efficient rooflight cost answer shows what changes a figure, while the costs page deals with quoting in general. The band below lists the main ones, and the guarantee page sets out the workmanship cover.

The order of work

Survey. The opening is measured and the old label is read.
Quote. A fixed written quote reflects what the survey found.
Unit ordered. Once the quote is accepted, the unit is ordered to suit the surveyed size.
Covering opened. The roof covering is opened round the position.
Structure trimmed. Where a new opening needs it, the structure is trimmed.
Kerb or frame fitted. The kerb or frame goes in and the edge is made watertight.
Lining finished. Inside, the lining is finished as agreed.

Glass, heat and damp: FAQ

What is the difference between a centre-pane and a whole-unit U-value?

A centre-pane figure covers only the glass in the middle. A whole-unit figure adds the frame, the spacer and the edges, so it matches the product as fitted. Ask for the whole-unit figure, and read rooflight U-values and Part L for how the limits apply.

Does triple glazing always make a rooflight better?

Not always. It lowers the glass U-value and keeps the inner pane warmer, but it is heavier and the frame and roof should suit. Which suits you turns on the room and its exposure. See triple-glazed rooflights for the weighing up.

Will solar control glass make my room dark?

Some makers' coatings and tints reduce the light a little, as well as the heat. The effect depends on the product, so we check the maker's light figures. A room that is already dim may be better with a vent and a blind. Details are in solar control glass for rooflights.

Why does moisture form on the inside of my rooflight?

Damp room air is touching cold glass. Better-insulated glass is warmer, and an extractor, an opening vent or an open blind all help clear the damp. Droplets between the panes mean a failed seal. Our condensation page has the checks.

What moves the price of an energy-efficient rooflight?

Glazing, frame, size, kerb, opening and blinds, plus how the roof is reached and what has to be strengthened. Nothing is priced from a photo, and the survey comes first. The cost answer goes factor by factor.

If only the glass is replaced, do the energy limits apply?

Fitting a new pane into the frame that is already there does not count as a controlled fitting, so the energy limits are not triggered by that job. Taking out the whole unit and fitting another is different, and the limits come into play. The survey reads the old label and tells you which case yours is.

Can an older or listed house have an energy-efficient rooflight?

The energy figures are the starting point, but listing changes the route: a new or altered rooflight on a listed building will almost always need listed building consent, and that consent decides the job. Our conservation rooflights page covers the slimmer, heritage-style units made for older roofs.

Can a rooflight vent help with damp air?

A vent that opens lets damp air leave a kitchen or bathroom, and some makers offer electric or solar-powered ones with remotes. Someone still has to open it each day. See electric-opening rooflights for the options.

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We handle the Building Regulations notification where the work is notifiable
10-year workmanship guarantee

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