What it costs: conservation area and listed building windows
Indicative UK prices for repairing, draughtproofing, reglazing and replacing period windows — each with its source and date, and the costs nobody quotes for.
Every figure below carries its source and the date that source itself claims. Most of the per-window numbers come from consumer price guides, which are averages across the whole market — not conservation-grade tender prices. Heritage joinery for a listed building routinely sits above the top of these ranges. Where nobody publishes a credible figure, this page says so rather than fill the gap. Nothing here is a quotation.
Money is usually the reason people arrive at this subject, and it is the part of it most poorly served online. Window companies publish price guides that stop at the product; heritage bodies publish excellent technical guidance that avoids numbers almost entirely; and the two costs that most often derail a conservation-area window project — professional fees, and the cost of doing it twice — appear in neither.
This page pulls together what is actually published, and is explicit about what is not. For the rules that decide which of these routes is even open to you, start with the complete guide and do you need planning permission?.
The cost hierarchy, according to the people with no product to sell
Before any numbers, it is worth knowing that the two statutory heritage advisers both rank the options on cost, and both rank them the same way.
Historic England, Traditional Windows: their care, repair and upgrading (HEAG039), §4.3, February 2017 revisionRepair, draught-proofing or secondary glazing is likely to be more cost-effective than replacement with double glazing.
Historic England, Modifying Historic Windows as Part of Retrofitting Energy Saving Measures, updated 23 July 2024Draught proofing will provide the biggest energy saving and conservation benefits for the lowest environmental and financial costs.
And the same source is blunt about the point of diminishing returns:
Historic England, Modifying Historic Windows…, updated 23 July 2024improvements beyond repair and draught sealing may not be cost effective in either financial or carbon terms
Historic Environment Scotland makes a related point about secondary glazing that is easy to miss and matters over twenty years:
Historic Environment Scotland, Managing Change in the Historic Environment: Windows, §4, updated 3 February 2020It can also be cheaper than replacement, and can be a more permanent solution than double-glazed units, whose performance will degrade over time.
None of that means replacement is never right. It means that if a quotation for full replacement is the only one you have obtained, you have not yet priced the options the advisers rank above it.
Repair and refurbishment
| Work | Low | High | Average |
|---|---|---|---|
| Sill splice | £120 | £240 | £180 |
| Sill replacement | £160 | £320 | £240 |
| Repair to stiles / front cheeks | £120 | £240 | £180 |
| Replacement sash | £270 | £400 | £335 |
| Sash cord replacement | £120 | £160 | £140 |
| Draughtproofing | £248 | £388 | £318 |
| Full sash refurbishment | £620 | £920 | £770 |
| Repainting sash and frame | £200 | £500 | per window |
The same publisher gives full sash refurbishment at £620–£920 in one cost guide and sash window restoration at £80–£488 in another, one month apart. We are not going to pretend that resolves into a tidy number. Treat £80–£920 as the honest published span, assume the low end describes light overhaul rather than full refurbishment, and insist on itemised quotations that state exactly what is included — cords, weights, beads, draught seals, glazing, decoration.
Two things worth budgeting for that quotations often omit. Repainting is a recurring cost, not a one-off: the same guide puts the interval at every five to ten years. And re-balancing is mandatory if you change the glass — see below.
Reglazing: slim-profile double glazing
Published prices here are for units supplied only, cut to size. They are not installed prices, and per-square-metre rates are not published by anyone we could find.
| Unit | Published price | Guarantee | Source |
|---|---|---|---|
| Heritage slim unit, 9 mm sightline, 12/14/16 mm overall, toughened, gas-filled | from £86.60 per unit, supply only | 2 years | UK Glass Centre (Westcountry Heritage), live July 2026 |
| "Heritage Slimline" 11 mm krypton unit | from £47.05 inc. VAT and delivery | 10 years claimed | glassdelivered.co.uk, live July 2026 — quoted during an advertised sale, so not a stable list price |
A real, currently-sold UK heritage slim unit carries a two-year guarantee, conditional on being glazed with the specified silicone. That sits awkwardly beside the “10 to 25 year” figures that circulate in sales material. Historic England’s own estimate of service life for slim units is “around 25 years”; a competitor’s sales table claims “less than 5 years”. Both ends of that argument are overclaiming — and the only UK field study, which re-measured units after two years, concluded that most changes were within the margins of error.
UK Glass Centre guarantee wording, live July 2026; Historic England, Modifying Historic Windows…, 23 July 2024; Historic Environment Scotland Technical Paper 20 (2013)
For what these units actually achieve thermally — measured in situ rather than claimed — see slim-profile double glazing in period windows.
Reglazing: vacuum insulated glazing
We could not find a single manufacturer, trade body or independent source publishing a UK price for vacuum insulated glazing per square metre or per window. The manufacturer says why:
AGC FINEO FAQ, live July 2026The cost varies greatly from one project to another … It is therefore difficult to provide an average cost per square meter.
Figures do circulate — a per-square-metre range, and a per-window figure for central London restoration work. Every one we traced led to an installer's marketing page or a personal blog, not to a manufacturer, a trade body or an independent publisher. So we are not repeating them, even with a caveat.
The honest position: vacuum glazing is quoted project by project. Expect a significant premium over slim-profile units, get at least three quotations for your actual sizes, and ask each supplier to price the joinery work separately from the glass so the quotations are comparable.
See vacuum insulated glazing in conservation areas and listed buildings.
Secondary glazing
| Item | Low | High |
|---|---|---|
| Secondary glazing, one window, including labour | £300 | £500 |
| Installation, hourly rate | £15 | £20 |
| Installation, day rate | £120 | £160 |
On a like-for-like basis this is the cheapest route to a meaningful thermal improvement, it needs no planning permission because it affects only the interior, and it generally needs no listed building consent either. Measured work put a single-glazed secondary unit at a 63% reduction in heat loss through the window — better than most of the slim double-glazed systems tested in the same programme.
See secondary glazing in conservation areas and listed buildings.
Replacement
| Replacement window | Range | Note |
|---|---|---|
| Timber sash window | £1,000 – £3,000 | Softwood at the lower end, hardwood such as oak or Accoya at the top |
| uPVC sash window | £600 – £1,200 | Usually refused on a principal elevation once an application is required — see uPVC in a conservation area |
| Aluminium sash window | £800 – £1,500 | |
| Sash window replacement, all types | average £1,300 | |
| New timber replacement window | from £1,450 | Quoted as a starting point, not an average |
| Double glazing, per window | £650 – £1,300 | General market figure, not heritage-specific |
Two adjustments to make to any of these before you use them for a conservation-area or listed building. First, they are whole-market averages: the specification that gets approved in a conservation area — correct glazing pattern, slender sightlines, horns where the period demands them, putty-profile finish, properly detailed meeting rails — is at the expensive end of joinery, and heritage work on a listed building routinely exceeds the top of the range. Second, if the original box frame survives and is sound, new sashes in the retained box is both a much smaller intervention and a cheaper one than a complete new window, and it is usually the stronger proposal in planning terms too.
The costs nobody quotes for
These are the ones that turn a budget into an overrun.
| Cost | Why it arises | What we can say about the amount |
|---|---|---|
| Re-balancing the sashes | Slim and vacuum units are heavier than the 4 mm single glass they replace — published slim-unit weights are 15–17.5 kg/m² against roughly 10 kg/m² for single glazing. Historic England describes "heavier weights added to balance the increase weight of glass". | Varies with window size and access. Any reglazing quotation that does not mention it is incomplete. |
| Sash alteration or renewal | Historic England: "Experience has shown that where slim-profile IGUs are inserted, window sashes often have to be replaced." The edge seal, not the overall unit thickness, drives the rebate — which is why glazing bars have to grow. | Effectively converts a reglazing job into partial replacement. Price it before committing. |
| Drawings and a heritage statement | Only needed where an application is required, but then usually a validation requirement. Authorities ask for large-scale joinery sections and dimensioned sightlines. | We found no published fee benchmark. Ask two or three practices. |
| Application fee | A householder application carries a statutory fee. Listed building consent is free to apply for. But see the box below: the exemption for applications caused only by an Article 4 direction no longer exists. | Fees are set nationally and change; check the current figure with your authority before budgeting. |
| A condition survey | If you are arguing that repair is not reasonably practicable, its absence is one of the commonest reasons appeals fail. | Cheaper than a refused application and a re-submission. |
| Doing it twice | Windows installed in breach, then required to be removed. In England the enforcement window for work completed on or after 25 April 2024 is ten years, not four. | The full cost of the job, twice, plus fees. See enforcement and selling the house. |
You will still find it said — including in otherwise careful guidance — that no application fee is payable where an application is only needed because an Article 4 direction has withdrawn your permitted development rights. That was true. It is not true now.
The exemption was regulation 5 of the Town and Country Planning (Fees for Applications, Deemed Applications, Requests and Site Visits) (England) Regulations 2012, headed "Exceptions – permission granted by General Permitted Development Order not applying". It was omitted with effect from 17 January 2018 by regulation 5(2) of the 2017 amending regulations, with a transitional provision preserving it only for applications already made before that date.
So budget for the normal householder fee. If a quotation, a blog or an installer tells you the application is free because of Article 4, it is working from pre-2018 information.
Fees Regulations 2012 (SI 2012/2920) reg.5, omitted 17 January 2018 by SI 2017/1314 reg.5(2), with the transitional provision at reg.7
Grants
Two national schemes get cited at people in this position, and neither pays for windows.
- The Energy Company Obligation (ECO4). GOV.UK describes the help available as “insulation work, for example to your loft or cavity walls” and “replacing or repairing your boiler — or other upgrades to your heating”. Windows and glazing are not among the measures named.
- The Great British Insulation Scheme. This one is simply over. GOV.UK states that installations had to be complete by 31 March 2026, when the scheme ends.
gov.uk/energy-company-obligation; gov.uk/apply-great-british-insulation-scheme, read 28 July 2026
We could not identify any current UK-wide grant for replacement windows or glazing upgrades in conservation areas or listed buildings, so we are not going to describe one. Two things are worth doing rather than assuming:
- Ask your own conservation team what is live locally. Heritage-led regeneration and townscape schemes do exist, are usually time-limited and area-specific, and are rarely well advertised. This is the one place worth real effort.
- Check any advertised “government grant for double glazing” against GOV.UK directly. It is a well-worn marketing line, and eligibility for energy-efficiency schemes generally turns on income, benefits or property characteristics — never on being in a conservation area.
How to get comparable quotations
- Price the options the advisers rank above replacement, even if you expect to replace. At minimum: overhaul and draughtproof; secondary glazing; reglaze the existing sashes.
- Ask for the joinery and the glass to be priced separately. It is the only way to compare suppliers who buy units from different makers.
- Ask for the guarantee in writing, with its conditions. A two-year unit guarantee and a twenty-five-year claim are not the same product promise.
- Ask explicitly whether the sashes will be altered, and by how much on the glazing bar face width. This is the question that determines whether you still have a period window at the end.
- Ask whether re-balancing is included.
- Get the specification on paper before the application goes in, not after. Changing it later means a fresh application.
- Do not pay for windows you do not yet have consent for. Refused applications happen, and deposits on bespoke joinery are rarely recoverable.
The value of the building. Conservation-area designation exists because the character of the area is worth something, and the windows are usually a large part of what a valuer and a buyer are looking at. That cuts both ways in a cost calculation, and it is the one figure only a local agent can give you.
Common questions
How much does it cost to replace windows in a conservation area?
There is no conservation-area surcharge in the price of a window itself, but the specification a conservation area pushes you towards is more expensive than a volume replacement. Consumer price guides put a timber sash window replacement at roughly £1,000 to £3,000 each and give an all-types average of about £1,300 (Checkatrade, cost guides updated June and July 2026). Heritage joinery for a listed building routinely sits above the top of that range, because those guides are averages across the whole market rather than conservation-grade tender prices. Add professional fees for drawings and a heritage statement where an application is required.
How much does it cost to refurbish rather than replace a sash window?
Substantially less than replacement, though the published figures are inconsistent. Checkatrade's sash window restoration guide gives full refurbishment as £620 to £920 per window, averaging £770, while its replacement guide lists sash window restoration at £80 to £488, averaging £284 — the same publisher, one month apart. Treat £80 to £920 as the honest published span and get itemised quotations. Individual repairs are cheaper still: a sill splice £120 to £240, a sill replacement £160 to £320, a replacement sash £270 to £400.
How much does draughtproofing a sash window cost?
Consumer price guides put draughtproofing at roughly £200 to £400 per window, with one guide giving £248 to £388 and an average of £318 (Checkatrade, July 2026). It is the intervention both Historic England and Historic Environment Scotland point to first on cost-effectiveness grounds: Historic England says draughtproofing gives the biggest energy saving for the lowest environmental and financial cost. Note what it does and does not do — measured work found no significant improvement in U-value but an 86% reduction in air leakage.
What does vacuum glazing cost in the UK?
No manufacturer, trade body or independent source publishes a UK price per square metre for vacuum insulated glazing, and AGC states in its own FAQ that cost varies so much between projects that it is difficult to give an average per square metre. Figures circulating online trace to installer marketing and personal blogs rather than to any manufacturer or independent publisher, so we do not repeat them. Expect a significant premium over slim-profile double glazing and obtain at least three quotations for your actual sizes.
How much does secondary glazing cost per window?
Consumer price guides put secondary glazing at around £300 to £500 per window including labour (Checkatrade, July 2026). That is generally the cheapest way to make a meaningful thermal difference to a period window while leaving the historic joinery untouched, and measured work by Historic Environment Scotland found secondary glazing reduced heat loss through the window by 63%, outperforming most slim double-glazed systems tested.
Is it cheaper to repair or to replace period windows?
The statutory heritage advisers say repair, and they say it on cost grounds as well as conservation grounds. Historic England's windows guidance states that repair, draughtproofing or secondary glazing is likely to be more cost-effective than replacement with double glazing, and its 2024 retrofit advice adds that improvements beyond repair and draught sealing may not be cost effective in either financial or carbon terms. Historic Environment Scotland makes the same point about secondary glazing, adding that it can be a more permanent solution than double-glazed units, whose performance will degrade over time.
Are there grants for windows in a conservation area or listed building?
Not from the schemes people usually have in mind. The Energy Company Obligation, ECO4, is described on GOV.UK as covering insulation work such as lofts and cavity walls, and replacing or repairing a boiler or other heating upgrades — windows and glazing are not among the measures named. The Great British Insulation Scheme is finished: GOV.UK states that installations had to be complete by 31 March 2026, when the scheme ended. We could not identify any current UK-wide grant for replacement windows or glazing upgrades in conservation areas or listed buildings. What does exist is local and time-limited — heritage-led regeneration and townscape schemes, usually area-specific and rarely well advertised — so ask your own conservation team what is live. Treat any advertisement offering a government grant for double glazing with scepticism and check it against GOV.UK directly.
Sources used on this page
Everything above is drawn from these. Where a source is dated, that is the version we read. If one has changed, tell us.
- Checkatrade — Sash window restoration cost — Consumer price guide; its own table states last updated July 2026. Repairs, draughtproofing, full refurbishment.
- Checkatrade — Cost to replace sash windows — Consumer price guide; table states last updated June 2026. Timber, uPVC and aluminium sash replacement.
- Checkatrade — Secondary glazing cost — Consumer price guide; table states last updated July 2026.
- Historic England — Traditional Windows: their care, repair and upgrading (HEAG039) — February 2017 revision. Section 4.3 on cost-effectiveness of repair versus replacement; Figure 118 sightline drawing.
- Historic England — Modifying Historic Windows as Part of Retrofitting Energy Saving Measures — Published 10 January 2023, updated 23 July 2024. Draughtproofing first on cost-effectiveness; slim unit service life around 25 years.
- Historic Environment Scotland — Managing Change in the Historic Environment: Windows — Updated 3 February 2020. Secondary glazing cost and permanence; true astragals; linseed putty and unit seals.
- Historic Environment Scotland — Technical Paper 1: Thermal performance of traditional windows — Measured 86% reduction in air leakage from draughtproofing with no significant U-value change; secondary glazing 63% reduction in heat loss.
- AGC FINEO — frequently asked questions — The manufacturer declines to publish an average cost per square metre for vacuum glazing.
- Histoglass — thin double glazing options — Published unit build-ups, minimum rebates, U-values and weights per square metre for five slim systems.
- UK Glass Centre — heritage double glazing unit, 9 mm sightline — A published supply-only unit price and guarantee period for a real heritage slim unit, live July 2026.
- Town and Country Planning (Fees for Applications, Deemed Applications, Requests and Site Visits) (England) Regulations 2012, regulation 5 — The fee exemption for applications needed only because permitted development rights did not apply — omitted with effect from 17 January 2018
- SI 2017/1314, regulations 5 and 7 — Regulation 5(2) omits reg.5 of the 2012 Fees Regulations; regulation 7 is the transitional provision preserving it for applications already made
- GOV.UK — Energy Company Obligation (ECO4) — Measures named are insulation and heating; windows and glazing are not among them. Read 28 July 2026.
- GOV.UK — Great British Insulation Scheme — Installations had to be complete by 31 March 2026, when the scheme ends. Read 28 July 2026.