Replacing windows usually starts in one of three ways. Something has stopped working, such as a window that will not close properly or a sealed unit that has misted up and cannot be cleared. The house feels cold and draughty, and the windows are the likely cause. Or the windows still work but have started to look dated and worn.
The questions that follow are much the same in each case: whether the windows genuinely need replacing or a repair would do, whether the frames or the glass can be changed on their own, what the regulations require of replacement windows, what it is likely to cost, and what the installation itself involves. This guide works through each in turn.
Window problems usually develop gradually, and many early signs can be checked at home in a few minutes without tools or a formal survey. The table below sets out what to look for, how to check it, and what the issue usually indicates.
|
Sign |
How to check it |
What it usually means |
|
Draughts around the frame |
On a windy day, hold a strip of tissue near the seal and check whether it moves |
The seals may have failed, or the opening section may have dropped |
|
Misting between the panes |
Look for condensation that cannot be wiped off either side |
The sealed glazed unit has failed; replacing the glass alone may be enough |
|
Stiff or dropped operation |
Open and close every window in the house |
Hinge or frame wear, sometimes adjustable |
|
Cold spots and noise |
Stand next to the window on a cold day and listen |
Single glazing or an ageing unit |
|
Discolouration or crazing |
Look at the frames in direct daylight |
Usually a cosmetic issue on uPVC windows |
|
Water on the inside sill |
Check after heavy rain |
Drainage or seal failure, worth acting on quickly |
Two signs carry particular weight. Misting between the panes confirms a specific fault, because trapped condensation means the seal has failed. Water on the internal sill is the most urgent, as it can damage surrounding plaster, timber and decoration if left unresolved.
Age is useful context, but not a verdict. Most uPVC windows last around 20 to 25 years, yet a 25-year-old window that still seals, opens and insulates properly does not need replacing. When two or more of the signs above appear together, replacement is usually better value than repeated repairs.
Often the glass can be replaced on its own; the frame rarely can. This is the question most homeowners want settled before anything else, so it is worth answering properly.
Where the frame is sound, the hardware works and the only fault is a misted or broken sealed unit, replacing the glass alone is usually the most practical option. The beading is removed, the failed unit is taken out, and a new unit is fitted into the existing frame. The work often takes under an hour per window and costs much less than a full replacement.
Glass-only replacement is less suitable in three situations. A distorted frame means the new unit may not sit correctly and could fail again. Worn hardware means the window will still feel draughty or stiff. And a single-glazed window has a frame that was never designed to hold a modern sealed unit, so it usually cannot be adapted reliably.
Changing window frames on their own is rarely practical. On a modern uPVC window the frame, opening section, sealed unit and hardware are designed as one system, so the frame is not a separate part that can be swapped while everything else stays in place. Removing the frame effectively means removing the whole window, which makes the job a full replacement in all but name.
Two rules cover most situations. Misting as the only fault on an otherwise sound window points to a glass-only repair. Two or more signs together, or a window past the 20-year mark, points to full replacement, because a partial repair on an ageing window can cost a meaningful share of a new installation while improving only one part of the system, and it carries none of the guarantee.
In that case, we can provide a free, no-obligation quote for your new replacements, window by window.
Replacement windows are made to measure, not bought from stock, so the process follows a clear sequence from first enquiry to installation and certification.
The gap between ordering and installation is the part most homeowners underestimate. Made-to-measure products cannot usually be rushed, so a project working towards a deadline, such as a house sale, should be planned backwards from the installation date with time allowed for survey, manufacture and fitting.
No. Window replacement can be phased over two or three stages, and there is usually no technical reason every window has to be replaced at the same time. Phasing has three practical implications worth knowing in advance.
Cost per window. Smaller batches usually cost more per window, because survey, delivery and installation are more efficient when several windows are done together.
Matching later orders. Frame profiles, foil colours and handle ranges change over time. Keeping a record of the full specification from the first order, including the profile name and foil reference, makes later batches far easier to match.
Guarantees. Each batch carries its own installation date and guarantee period, so the paperwork for each stage should be kept separately.
Where a project is split, the windows in the poorest condition come first, then the coldest or noisiest rooms. Completing one elevation at a time avoids a visibly mismatched frontage. In conservation areas and period properties, phasing is often a necessity rather than a choice.
In short: replacement windows in England must meet current thermal standards even in an older house, the work must be registered with the local council, and a window that serves as an escape route must still provide a big enough opening. The detail:
Since June 2022, replacement windows must achieve a U-value of 1.4 W/m²K or better, or a Window Energy Rating of Band B or better. This rules out single glazing and many older sealed units, and the standard applies to each window, not as an average across the project. U-values are explained properly in our guide to how double glazing works.
Habitable rooms on the ground floor, and on upper storeys up to 4.5 metres above ground level, generally need a window or door suitable for escape. Where required, Approved Document B sets a minimum clear openable area of 0.33 square metres, at least 450mm high and 450mm wide, with the bottom of the opening no more than 1100mm above floor level. A replacement for an existing escape window must provide at least the same escape potential. This is often overlooked, and it directly affects which window opening functions qualify, because not every design opens wide enough.
Replacement windows are notifiable work and must be registered with the local council. A FENSA-approved installer self-certifies the installation and issues a certificate confirming Building Regulations compliance, energy-efficient products and council registration; a non-registered installer means arranging and paying for a building control inspection instead. Solicitors routinely request the certificate when a property is sold, so missing paperwork causes real conveyancing problems.
Like-for-like replacement is usually permitted development and needs no application. Listed buildings require listed building consent, and conservation areas or an Article 4 direction can restrict materials and style. Requirements differ in Scotland, Wales and Northern Ireland.
The main choices are material, glazing, opening style, appearance, colour and specialist glass. Most are straightforward. Opening style deserves the most thought, because it affects daily use, cleaning, ventilation and escape, and changing it later means replacing the window again.
uPVC is the most common choice for UK replacement windows because it is affordable, energy efficient and low maintenance, which is a large part of why uPVC windows are so popular. Timber and aluminium are usually chosen for appearance or heritage requirements.
Double glazing meets current standards and suits most homes. Triple glazing improves heat retention, and is most useful on exposed elevations and in north-facing rooms; whether triple glazing is worth it depends on the room and the budget.
The opening function is the decision homeowners most often get wrong, and the hardest to change later:
Three checks settle most opening-style decisions: whether the room needs an escape window, whether the outside glass can be cleaned safely, and whether an outward-opening unit would obstruct a path, driveway or boundary.
The window style should match the property and, on period streets, the neighbouring homes. Frame thickness, glazing bars and the proportions of the opening lights usually affect the appearance more than colour does.
Frames come in a range of foil finishes, with the inside and outside often available in different colours, and handles are available in matching finishes. The full range is shown on our colour options page.
Obscure glass suits bathrooms and overlooked windows, solar-control glass reduces heat from the sun, laminated glass improves security and reduces noise, and toughened glass is required in certain locations, including low-level glazing and glass beside doors. The choices are covered on our glass options page.
Every window is made to measure, and every property brings different installation requirements, so a final quotation after an on-site survey is the most reliable. Initial estimates can be sought using simple measurements or photos, and as a broad indication, a standard uPVC casement window typically falls in the region of £400 to £900 supplied and fitted depending on size and specification. According to the Federation of Master Builders, a whole semi-detached house of eight to ten windows commonly lands between £6,000 and £9,000. Four factors move the price most:
Size. Larger openings need more frame material, more glass, stronger hardware and more handling during installation.
Number of windows. Survey, delivery and fitting costs are spread across the project, so the cost per window falls when more are replaced at once.
Glazing specification. Triple glazing costs more than double glazing, and laminated, acoustic and obscure glass all add to the price.
Access. Upper floors, restricted rear access, bay windows and scaffolding requirements all increase labour time.
The fastest way to a real figure is a free, itemised quote, fixed after survey.
Window installation is quicker and cleaner than major building work, but it is still disruptive, and it is better to know that in advance than to be told it will be effortless.
In the week before, curtains, blinds, nets and fittings around the windows should come down, and ornaments and pictures should be moved away from sills and nearby walls, because removing old frames causes vibration. About a metre of clear space in front of each window helps; installers can move heavy furniture, but a clear room makes the work faster.
The team typically arrives early, agrees the order of work room by room, and protects floors and surfaces. An adult needs to be at the property while work is taking place. Windows are replaced one at a time: the old frame and glass come out, the opening is checked, and the new window is fitted, levelled, fixed and sealed. Dust is most noticeable while old frames are being removed. Work continues in most weather, though heavy rain or strong wind can delay fitting.
A typical house of eight to ten windows takes two to three days. Any opening started in a day is finished and sealed the same day, so the house is never left open overnight. Once fitting is complete, trims and sealant are finished inside and out, old frames and glass are taken away, and the property is cleared and swept. At handover, the installers demonstrate how each window opens, locks and operates for cleaning, including any restrictors; guarantee documents are provided, and the FENSA certificate follows once the installation is registered. On older properties, a small amount of plaster or decoration around the reveal may need attention after the old frame comes out.
At DOVISTA, we manufacture and install uPVC windows and doors for homes across Milton Keynes, Northamptonshire, Bedfordshire, Buckinghamshire, Cambridgeshire and Hertfordshire. We are Danish owned, we have been making windows since 1941, and we are FENSA and BFRC certified, with Building Regulations compliance registered as part of every installation.
The practical questions that decide any window project have straight answers here:
The full range of styles, opening functions, colours and hardware can be seen and handled at our Milton Keynes showroom, and every project starts with a free, written, no-obligation quote.