Updated 26 October 2026 · SK Home Improvements
Replacement windows swap old frames and glass for new, more energy-efficient units. Most homes choose between uPVC, aluminium and timber, with double or triple glazing. Replacement windows typically cost £4,500–£9,000 including VAT for a house, and the work must meet Building Regulations through a registered installer or building control.
What should you consider when choosing replacement windows?
When choosing replacement windows, start with four things: the frame material, the glazing, the opening style and the look of your house. The right mix depends on your budget, how much maintenance you are happy with, the age and style of the building, and whether planning rules limit what you can change.
It also helps to think about how each room is used. Bedrooms on upper floors may need windows large enough for escape in a fire, rooms by a busy road benefit from acoustic glass, and bathrooms usually need obscure glass. A survey measures every opening and checks the condition of the brickwork and lintels around them before anything is ordered.
How do uPVC, aluminium and timber windows compare?
uPVC is the most common and usually the most affordable choice, aluminium gives slimmer frames and a modern look, and timber suits older and period homes. The table compares typical features; actual performance depends on the product.
| Material | Typical lifespan | Maintenance | Relative cost | Suits |
|---|---|---|---|---|
| uPVC | 20–35 years | Wipe clean, check seals and hinges | Lowest | Most post-war and modern homes |
| Aluminium | 30–45 years | Wipe clean; powder-coated finish | Higher | Modern homes, large panes, slim sightlines |
| Timber | 30–60 years with care | Repaint or re-stain every 5–8 years | Higher | Period homes, conservation areas, listed buildings |
Modern aluminium frames include a thermal break, a plastic barrier inside the frame that stops heat escaping through the metal. Composite windows, with timber inside and aluminium outside, combine a warm interior look with a low-maintenance exterior, at a higher price.
Should you choose double or triple glazing?
Double glazing suits most UK homes, while triple glazing makes most sense where you want extra warmth or quiet and the rest of the house is already well insulated. A modern double-glazed unit with a low-emissivity coating, argon gas between the panes and a warm-edge spacer bar performs far better than double glazing from the 1980s or 1990s.
- Triple glazing: lower heat loss and better sound reduction, but heavier, thicker and more expensive, and it lets in slightly less daylight.
- Acoustic glass: laminated glass with a sound-dampening layer, useful near main roads, railways or flight paths.
- Safety glass: toughened or laminated glass is required in critical locations, such as glazed doors and low-level glass near floors and doors.
- Obscure glass: patterned glass for bathrooms and side windows facing neighbours.
What do window energy ratings mean?
Window energy ratings show how well a whole window keeps heat in, and are given as a U-value, a Window Energy Rating, or both. A U-value measures heat loss in watts per square metre per degree (W/m²K): the lower the number, the better. A Window Energy Rating, from A++ down to E, also accounts for heat gained from sunshine and air leakage.
In England, replacement windows are generally expected to achieve a U-value of 1.4 W/m²K or better, or a Window Energy Rating of band B or better. Wales, Scotland and Northern Ireland set their own, broadly similar standards. Always ask for the rating of the whole window, not just the glass, because the frame affects performance.
Which window styles are available?
The main window styles are casement, tilt-and-turn, sash and fixed, and the right one usually depends on the age of the house and how you want to open and clean the windows.
- Casement: side- or top-hung sashes that open outwards. The standard choice on most UK homes.
- Tilt-and-turn: tilt inwards from the top for ventilation, or swing fully inwards for cleaning and escape. Useful on upper floors.
- Sliding sash: vertical sliders that suit Victorian and Edwardian homes. Available in timber and in uPVC or aluminium designs made to look traditional.
- Fixed lights: panes that do not open, used alongside opening windows or for large picture windows.
For doors to the garden, see our guides to bifold and sliding doors and front and back doors.
Do replacement windows need Building Regulations approval?
Yes. Replacement windows are controlled work under Building Regulations across the UK, covering energy efficiency, ventilation, safety glass and, on upper floors, escape in a fire. In England, Wales and Northern Ireland the work must either be self-certified by an installer registered with a government-authorised competent person scheme or approved by building control. In Scotland, like-for-like replacement windows do not usually need a building warrant, but they must still meet the building standards.
- Ventilation: in England, replacements usually need trickle vents or another means of background ventilation, and ventilation must be no worse than before.
- Escape: bedrooms and other habitable rooms on upper floors may need an escape window with a large enough opening at a reachable height.
- Certificate: keep the completion certificate, as buyers' solicitors ask for it.
Our guide to Building Regulations explains the approval routes in each nation.
Do you need planning permission for new windows?
Replacing windows on a house usually does not need planning permission if the new ones look broadly similar to the old ones. Permission or consent is more likely to be needed for flats, for listed buildings, in conservation areas and where an Article 4 direction removes the usual rights in England or Wales. Listed buildings need listed building consent for almost any change to windows, and councils often expect repair or like-for-like timber.
Changing the size of an opening or adding a new window can also need permission, and side-facing upper windows may need obscure glass. We check this before quoting; our planning permission guide has more detail.
How much do replacement windows cost?
Replacement windows for a house typically cost £4,500–£9,000 including VAT, depending on how many windows you need, their size, the frame material and the glazing. uPVC usually costs least, with aluminium and timber costing noticeably more. Triple glazing, acoustic glass, sash designs, coloured or wood-effect finishes and specialist hardware all add to the price, as do scaffolding for upper floors and repairs to rotten sills or failing lintels.
Fitting usually takes one to three days for a typical house, with each opening out for only a few hours. Get a range for your home from our guide-price tool, then book a free site survey for a written quote.
Related services
- Replacement windows: guide £4,500–£9,000 inc VAT
- Front and back doors: guide £1,000–£3,500 inc VAT
- Bifold and sliding doors: guide £3,000–£8,000 inc VAT
Figures in this guide are typical UK ranges including VAT where it applies. They are not quotes. Rules on planning and building control differ between England, Wales, Scotland and Northern Ireland and change over time, so we check what applies to your property before quoting.