Which roof window brand is best?
There is no single answer, and anybody who gives you one without asking about your roof is selling something. VELUX, Fakro, Keylite and Roto all make competent manufactured roof windows to the same European standards, all four carry manufacturer warranties on the glass and frame, and on a straightforward interwar semi at Longlevens any of them would still be doing its job in twenty-five years. What separates them is the fit against a particular roof, a particular size constraint and a particular set of accessories, and that is a survey question rather than a brand question. Severn installs all four. What follows is what actually differs between them and which of those differences will matter to you. The installation detail, which is the same whichever badge is on the frame, is on the roof window installation page.
The roof narrows the field before the badge does
Start here, because it usually removes half the question. A roof covering, a rafter spacing and a run of slope between them determine a small set of workable sizes, and not every manufacturer makes every size. On a trussed estate roof at Quedgeley or Bishops Cleeve with 600mm centres, the requirement is a frame around 550mm wide, and the ranges that offer one at the height you need are the ranges in contention. On a Victorian rear addition in Gloucester with 1.9 metres from gutter to abutment, the height code is capped and again some grids reach it and some do not.
The same applies to the covering. Every manufacturer produces flashing kits, but the depth of profile each one covers varies at the extremes, and a deep clay pantile or an unusually thick slate can rule out a kit before it rules out a window. On Cotswold stone slate at 20 to 30mm laid in diminishing courses, none of the four has a kit drawn for the covering, and the conversation moves to a conservation rooflight instead. Establish the roof’s constraints first and the brand question is often already half answered.
What the four have in common, which is most of it
Before the differences, the shared ground is worth stating because it is large. All four build a laminated pine frame and sash as the standard product, with a factory preservative treatment and a water-based lacquer or paint. All four clad the outside in coated aluminium, usually in a dark grey. All four offer a white-finish polyurethane variant for bathrooms and kitchens.
All four make centre pivot and top hung ranges, rate them from about 15 degrees upward, supply a boxed flashing kit matched to the covering profile, and fit a ventilation flap with a filter at the head. All four supply blinds, insulation collars, underlay collars and electric openers as accessories against their own codes. The construction principles are common property, and so is the physics: the perimeter detailing decides whether an installation stays dry, and no manufacturer’s frame changes that.
Where the four genuinely differ
The real distinctions are narrower than the marketing suggests and they are mostly about hardware, standard inclusions and the shape of the range.
| Range | Origin | What is distinctive about it | Where that tends to matter |
|---|---|---|---|
| VELUX | Danish, the oldest of the four | The widest accessory catalogue and the deepest stock holding in UK merchants | Getting a blind or a component years after the window went in |
| Fakro | Polish | A broad hardware range, including higher pivot positions and top-hung variants with a wide opening angle | Steep roofs where head height and reach are awkward |
| Keylite | Northern Irish | An insulation collar supplied fitted to the frame as standard rather than as a separate item | Consistency of the thermal detail around the perimeter |
| Roto | German | Hardware engineering and pivot geometry, with widths that sit slightly off the common grid | Openings that do not land neatly on another maker’s size steps |
Those are characteristics rather than rankings. The Keylite collar, for instance, is a genuinely useful inclusion, and it is also a component the other three supply as a boxed accessory that gets fitted anyway on a properly detailed job. The Fakro pivot position is worth real money on a 45 degree Forest of Dean slate roof where the handle would otherwise be out of reach, and worth nothing on a 25 degree suburban hip.
Size grids do not cross, and that matters later rather than now
Each manufacturer runs its own grid of widths and heights with its own code system. The nominal sizes are similar but not identical, often within twenty or thirty millimetres of each other, and the codes describing them are unrelated notations. Nothing about that is a problem at the point of ordering. It becomes a problem afterwards.
Every accessory orders against the brand’s own code: the flashing kit, the blind, the awning, the insect screen, the insulation and underlay collars, the electric opener, the remote. A blind bought for one maker’s nominal size will not fit another maker’s frame of the same nominal size. So the practical consequence of choosing a brand is that you have chosen the ecosystem for the life of the window, and if two windows on the same elevation come from different ranges their blinds will never match and they cannot share a combination flashing. The coding systems themselves are set out on the roof window sizes and how they are coded page, and whether standard sizes are constraining is answered under do roof windows come in standard sizes.
Frame material, finish and the room below
All four offer the same three basic frame types and the choice between them is driven by the room rather than the badge. Clear-lacquered pine suits a bedroom or a study and wants redecorating every three to five years. Painted white timber suits a room where the frame should disappear into the ceiling. White polyurethane over a timber core suits a bathroom, a wet room, a kitchen or a utility, and removes the coating interval altogether.
External cladding colour is where a small difference shows. Standard is a dark grey across all four, and each offers factory colour finishes to specified references, though the standard palettes and lead times vary. Where a conservation area condition sets a black or dark finish, the reference has to be on the order rather than applied afterwards, and it is worth checking which range holds the required colour in stock before committing. Redecoration and finishes are covered on the can a roof window be painted page.
Glazing, and the numbers that are nearly identical
This is where people expect the biggest difference and find the smallest. A current double-glazed manufactured roof window from any of the four sits somewhere around 1.0 to 1.4 W/m2K for the whole unit, comfortably inside the 1.4 limiting standard that current guidance sets for a replacement. Triple-glazed options from all four go lower again, into the 0.7 to 1.0 region.
The options list is broadly common too: toughened outer panes, laminated inner panes where there is habitable space beneath, low-emissivity and solar control coatings, self-cleaning outers and acoustic laminates. What differs is which are stocked and which are a special order, and that shows up as lead time rather than as capability. The questions worth spending time on are the coatings and the laminated inner pane, not the badge, and those are on the energy efficient rooflights page.
Availability, lead time and finding a component in ten years
This is the argument that carries the most practical weight and it gets the least attention. A roof window is in the roof for twenty-five years. In that time you may want a replacement blind, a new gasket length, a filter, a fresh sash catch or a flashing kit for a re-covered roof.
What matters there is how long a range stays in production, how well merchants stock it, and how easily a part can be identified from the plate on the sash. That favours the ranges with the deepest UK distribution, and it is a genuine reason to think twice before choosing a brand purely on a price difference at order stage. Lead time on the initial order matters too, particularly where scaffold is booked: a window held in stock at a local merchant can be fitted the following week, and one on a four-week special order sets the programme. On a job in the Stroud valleys where scaffold has to be hand-carried in, that difference is worth more than the specification detail people argue about.
Replacing a unit already in the roof, where the choice is half made
On a replacement the calculation changes. An existing frame carries a size code on a plate behind the ventilation flap, and staying within the same range usually means the new unit lands close to the same fixing line and the existing opening needs little adjustment. Changing range on a like-for-like swap often means the structural opening has to be altered by twenty or thirty millimetres, which is not difficult with the covering off, but it is work.
Two exceptions. Where the old window is from a discontinued range or a maker no longer supplying the UK, the choice is open and should be made on the criteria above. And where a whole elevation of three or four units is being replaced together, the sensible move is to bring them all into one current range so the glass, the frames and the blinds match across the roof rather than drifting through three product generations. What tends to be waiting under an old frame is on the replacing a failed or misted rooflight page.
How the choice actually gets made at a Gloucestershire survey
In order, and the brand name enters late. The rafter or truss centres and the run of slope fix the workable sizes. The covering and its profile height fix the flashing kit family. The pitch and the room use decide centre pivot or top hung, and where the handle can be reached from. Escape and ventilation requirements decide whether the unit has to open and how far. Only once that is settled does it emerge which ranges offer the size, the kit and the specification together, and frequently more than one does.
Where the county pushes the answer is fairly predictable. Trussed estates at Quedgeley, Abbeydale, Bishops Cleeve and Yate need the narrow widths and the ranges that make them. Forest of Dean cottages at Coleford and Cinderford at 40 to 45 degrees push towards hardware that puts a handle within reach, or towards an electric opener. The vale terraces through Gloucester, Longford and Tewkesbury are constrained by run of slope above all. Central Cheltenham’s shallow hidden mansard slopes are often below the pitch any of the four is rated for, which moves the answer to a kerb-mounted unit entirely, and the Cotswold stone slate roofs through Painswick, Bibury and Northleach move it to a conservation rooflight. Where a manufactured window is the right product, the range options and codes are on the VELUX window installation page, and the survey notes record which ranges were considered and why one was recommended.
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