This page groups the most useful double glazing questions by topic, so you can jump to the part of the job you are weighing up, whether that is the budget, the frame material, funding, the fitting itself or what happens once the installers leave. For the specific search-style queries people type into Google, see our double glazing questions answered page, and to price up your own home put the numbers into the uPVC window calculator.
Every figure here is reconciled to our 2026 data and cross-checked across Checkatrade, the FMB and GreenMatch. Use the categories below as a reference, then dig into the linked guides where you want the full working behind a number.
Want the headline cost answer first? Our cost per window guide sets the scene before you read on.
Costs and value
Most homeowners want a budget before anything else. These answers cover whole-house ranges, deposits and resale value, and tie back to the full breakdowns in our cost by style and material hub.
Costs and value
Most UK homeowners pay between £4,000 and £10,000 to replace all windows in an average semi-detached house in 2026. A flat might cost £1,800 to £5,000, while a large detached home can reach £7,000 to £16,500 or more, depending on the number of windows, frame material and glazing.
Work out your window count, then apply a per-window range. As a guide, a flat with around 4 windows runs £1,800 to £5,000, a terraced house with around 7 windows £3,200 to £7,000, a semi-detached with around 10 windows £4,000 to £10,000, and a detached home with around 14 windows £7,000 to £16,500. Add a contingency of 10% or so for unexpected reveals or sill repairs.
A deposit of 10 to 25% is normal once you sign, because the installer orders bespoke frames to your measurements. Never pay the full balance up front, and pay the final amount only after the windows are fitted and you are happy with the work. Card or finance payments give you more protection than a bank transfer.
It can. Buyers expect efficient windows, so tidy, well-fitted double glazing protects your asking price and avoids a survey red flag, even if it rarely adds its full cost back. The bigger wins are lower energy bills and a warmer, quieter home while you live there.
Materials and styles
The frame material and window style drive both the look and the price. These answers help you pick between uPVC, aluminium and timber, and between casements, sash and other styles, with more detail in our uPVC versus aluminium comparison.
Materials and styles
Yes. uPVC is the most affordable frame material, typically around 35% cheaper than aluminium and roughly 90% cheaper than timber, while still delivering excellent thermal performance. Aluminium costs more but offers slimmer frames and a sleek, modern look.
uPVC is the best-value all-rounder for most modern homes, with low maintenance and excellent insulation. Aluminium suits a sleek, modern look with slim frames and is very durable. Timber is the premium choice for period and listed properties where the look has to match. For a side-by-side view, read our uPVC versus aluminium comparison.
Sash windows suit Victorian and period homes and keep the original proportions, typically £600 to £1,500 per window in uPVC and more in timber. Casements remain the most versatile and affordable choice for most modern UK homes, from £400 to £1,000 in uPVC.
uPVC and aluminium come in a wide range of colours and woodgrain foils, including anthracite grey, black and cream, usually for a small premium over white. Timber can be painted or stained to any shade. Coloured or dual-colour frames (one shade inside, another out) add to the lead time, so confirm this when you order.
Grants and funding
Funding can cut the bill for some households, but the rules are narrow and change often. These answers cover the 2026 schemes and how to check eligibility; see the full picture in our grants guide.
Grants and funding
ECO4 was extended and now runs to 31 December 2026, with no successor scheme after it. In England the Warm Homes: Local Grant is the headline scheme, offering up to £15,000 for fabric measures including glazing for households with income under £36,000 or on benefits, in EPC bands D to G, and it is open to 2028. Only around 15% of households qualify for funding overall, so check eligibility before assuming free windows.
Yes. Home Energy Scotland offers an interest-free loan of up to £8,000 for energy-efficiency measures, rising to up to £9,500 in rural areas. It is a loan rather than a giveaway, so you repay it over time, but the zero interest makes it a low-cost way to spread the cost of new windows.
Eligibility usually depends on your income or benefits, your EPC band and your property. For the Warm Homes: Local Grant the broad test is income under £36,000 or being on qualifying benefits, with an EPC of band D to G. Run your details through our grant eligibility checker first, then confirm on GOV.UK before you commit, because rules change often.
Installation and process
Once you have chosen your windows, the buying and fitting process is fairly predictable. These answers walk through quotes, fitting day, access and certification, and link to our FENSA explained guide for the compliance detail.
Installation and process
A typical installer fits 4 to 6 windows per day, so an average house is usually completed in 1 to 3 days. Larger homes or complex installs such as bay windows can take a little longer.
Usually not. Replacing like-for-like windows falls under permitted development. However, listed buildings and homes in conservation areas often need consent, so always check with your local planning authority first.
Most jobs follow the same path: get at least three written quotes, choose your frame material and glazing, agree a fitting date and pay a deposit, then the installer measures up and orders your bespoke frames. On fitting day they remove old windows one at a time, fit and seal the new units, and finish with the certification paperwork.
Someone should be home to give access and approve the work, though you do not have to watch every minute. A tidy installer uses dust sheets and clears up afterwards. Expect some plaster or pointing touch-ups around the reveals, which most firms include, so ask whether making good is part of your quote.
FENSA is a government-authorised scheme that lets registered installers self-certify that replacement windows meet Building Regulations. Your certificate is proof of compliance and you will need it when you sell the house, so always use a FENSA or equivalent registered fitter and keep the paperwork safe.
Guarantees and aftercare
Good windows should last decades with little fuss, but it pays to know what your guarantee covers and how to keep them in good order. These answers cover lifespans, cleaning and what to do if a unit fails; for more on longevity see our lifespan guide.
Guarantees and aftercare
Quality double glazing lasts around 20 to 25 years for uPVC frames, 30 to 40 years for aluminium, and 30 to 60 years for well-maintained timber. The sealed glass unit itself typically lasts 15 to 20 years before any misting. Most reputable installers offer a 10-year guarantee.
Most reputable installers offer a 10-year guarantee covering frames, glass units and the fit. Check whether it is insurance-backed, which protects you if the company stops trading, and read what is excluded, such as accidental damage or condensation caused by poor ventilation rather than a faulty unit.
uPVC and aluminium need little more than a wipe with warm soapy water a few times a year; avoid abrasive cleaners on the frames. Timber needs repainting or restaining every few years to stay weatherproof. Lubricate hinges and locks once a year, and keep trickle vents clear so the room can breathe and the glass stays mist-free.
Internal misting between the panes means the sealed glass unit has failed and lost its gas or developed a leak. The frame is usually fine, so only the glass unit needs swapping. If it happens within your guarantee period, the installer should replace it free of charge, so report it in writing as soon as you spot it.
Still pricing up a job? Compare your numbers against ours in the calculators hub before you sign anything.