Glazing, Windows & Draught-Proofing: EPC points and cost

Does double glazing improve your EPC rating? Far less than you would think

Yes, double glazing improves an EPC, but far less than almost everyone expects, and at the worst cost per point of any common measure. This page exists to give you the honest maths before you spend, because the window industry sells glazing as an EPC upgrade while the documented arithmetic tells a very different story.

In a published landlord case study (STATUS: documented, The Independent Landlord, Suzanne Smith), £5,400 of new front-elevation double glazing added exactly +2 points to the certificate, per the property’s own EPC recommendation report. That is roughly £2,700 per point, the single worst value of any common improvement, and about twenty-five to fifty times the cost per point of loft insulation. Published ranges for a whole-elevation glazing job run from +2 up to +10 points for £3,000 to £6,000-plus, so even at the optimistic end it is expensive per point.

The reason is structural. A domestic EPC is a SAP rating from 1 to 100 that models running cost per square metre from the whole building, walls, roof, floor, windows, heating, hot water and lighting. Windows typically carry only around 10 to 15% of the score’s weight, so replacing them can only ever move the number modestly, no matter how good the new units are. The big drags on the score are walls and roof, not glass.

So the honest verdict, which we lead with rather than bury: fit double glazing for comfort, noise, condensation and sale appeal, not for EPC points. If points are the goal, your money goes far further on insulation, controls and the quick wins. If comfort, a quieter home, warmer rooms and a better-presented property are the goal, glazing can be entirely worth it on its own terms. Just do not buy it expecting a band jump.

Draught-proofing: the cheap sibling win

Here is the measure the glazing salesman will not mention: draught-proofing delivers a slice of the same warmth-and-comfort benefit for 1 to 2% of the cost. At £30 to £250 for doors, windows and floors, typically adding +1 to +3 points, draught-proofing lands at roughly £30 to £150 per point, a fraction of glazing’s cost per point, and it improves the performance of everything else in the home. If your real problem is cold draughts around old windows and doors, draught-proofing is very often the smarter first spend. For where it sits among the other low-cost measures, see our cheapest EPC improvements.

What glazing costs, and the cost per point verdict

• Whole-elevation double glazing (uPVC): typically £3,000 to £6,000-plus, for a documented +2 up to +10 points. That is roughly £1,000 to £2,700 per point, the worst of the common measures.
• Secondary glazing (the heritage-safe option): varies, but the key point is that it is scored on the certificate and is usually the only consent-compliant route on listed buildings.
• Draught-proofing: £30 to £250, +1 to +3 points, roughly £30 to £150 per point, the cheap sibling.

The cost-per-point verdict is unambiguous and we will not soften it: new double glazing is the most expensive way to buy EPC points, full stop. For a like-for-like comparison against every other measure, see our cost per point breakdown. Owners who genuinely need the number moved should look first at insulation, where a loft top-up buys points at around £50 to £100 each, and at the cheapest EPC improvements hub.

To put the maths in the context of a real plan: a home sitting at 66 points, three short of the 69-point band C threshold, could reglaze the front elevation for £5,400 and, on the documented arithmetic, still fall short of C at +2 points, having spent thousands. The same three points typically come from a £25 cylinder jacket, £60 of LED lamps and £420 of heating controls, with change to spare. That is the case for spending on fabric and controls before glass, laid bare.

Who glazing is right for, and on what grounds

Glazing is worth doing, but justify it correctly:

• Owners chasing comfort, not points. Cold rooms, a noisy road, condensation on single-glazed panes, and draughty old frames are all real reasons to reglaze. The comfort and presentation benefits are genuine, the EPC uplift is a modest bonus, not the reason.
• Sellers presenting a property. New windows lift kerb appeal and buyer perception in a way the EPC number does not capture. That can be a sound investment even though the certificate barely moves.
• Homes with genuinely failed or single-glazed windows. If the existing units are past economic repair, replacement is justified on its own merits and the few EPC points come free with the job.
• Heritage owners, but via secondary glazing, not uPVC (see the building-type note below).

Who glazing is not right for: anyone whose primary aim is a band jump on a budget. For them, the money is far better spent elsewhere.

Whole-window replacement is a Medium-disruption measure (fitters in for a day or two, some making-good); draught-proofing is Low-disruption and often a same-day job.

Glazing by building type: solid-wall period stock and heritage homes

Where glazing sits in the plan depends heavily on the property, and two archetypes are worth calling out because they generate most of the confusion.

Pre-1919 solid-wall terraces. These are the homes where owners are most often pushed toward expensive glazing “to reach C”. The documented worst-case example on this exact stock, a late-Victorian solid-wall mid-terrace, went from EPC E (48) to a high C (77) for around £8,550 in total, and the glazing (£5,400 of it) contributed just +2 of that 29-point gain; the points came from an £800 loft top-up and floor insulation. The lesson for this stock is unambiguous: sequence the loft, floor and controls first, and treat glazing as a comfort upgrade rather than the route to the band. Our insulation guide covers the fabric measures that actually move a solid-wall home.

Listed and conservation-area homes. Here glazing is not just poor value on the EPC, it is often constrained. Replacement uPVC double glazing is routinely refused listed-building consent, so the consent-safe route is secondary glazing, a discreet second pane fitted behind the original window, which preserves the historic fabric and is still scored on the EPC under RdSAP 10. Where consent for external glazing changes is refused on a rented listed property, that refusal can itself support a registrable MEES exemption (third-party consent), so the constraint is recognised in the compliance regime rather than left as a dead end.

Across both archetypes the conclusion is the same: on the certificate, glass is rarely where the points are, it is where the comfort and, on heritage stock, the consent complications are.

RdSAP 10 evidence: the FENSA or CERTASS certificate

Since 15 June 2025 (STATUS: in force), domestic assessments use RdSAP 10, and two things changed for glazing.

First, every window is now measured individually rather than the old “typical window area” assumption. That means unusual glazing layouts are finally scored accurately, sometimes up, sometimes down, so the effect on any given home is genuinely property-specific.

Second, evidence is worth points. Have ready for your re-assessment:

• The FENSA or CERTASS certificate for the replacement windows, this is the RdSAP 10 evidence document. (If the work was signed off by building control directly, that sign-off serves the same purpose.)
• The installation invoice and any product/U-value data for the units.

Under RdSAP 10, glazing you cannot evidence may be scored on default assumptions, so keep the certificate with the rest of your improvement paperwork.

Grants and 0% VAT

There is no dedicated grant for replacement double glazing for owners, do not expect one, and be cautious of anyone implying otherwise.

What applies is the tax position: 0% VAT on energy-saving materials covers qualifying draught-proofing and insulation on residential accommodation in Great Britain until 31 March 2027, after which it reverts to 5% (STATUS: law, VAT Notice 708/6). Note the scope carefully, the zero rate targets energy-saving materials such as insulation and draught-stripping; confirm the position for any specific glazing or draught-proofing product on the GOV.UK notice, since scope matters. You can check the detail at 0% VAT on energy-saving materials (Notice 708/6) on GOV.UK, and see the full picture on our grants and funding page.

The genuinely useful grants in this niche sit elsewhere, the £7,500 Boiler Upgrade Scheme for a heat pump, and household-eligibility schemes for insulation and heating, not on the windows.

When glazing is the WRONG first move

For a points-driven owner, glazing is almost always the wrong first move. Specifically, do not lead with double glazing when:

• Your goal is a band jump for the least money. At ~£1,000-£2,700 per point it is the most expensive route to the 69-point band C threshold. The quick wins, insulation and controls get you there for a fraction of the cost, start with the cheapest EPC improvements.
• Your real problem is draughts. Draught-proofing at £30 to £250 solves much of the comfort issue at 1 to 2% of the reglazing cost.
• You are a landlord planning for 2030. The confirmed EPC C by 1 October 2030 standard for privately rented homes is measured across two of the reformed metrics including fabric performance (STATUS: confirmed government policy, 21 January 2026, awaiting secondary legislation reported for 2027). Windows are a small fabric contributor; loft, cavity and floor insulation move the fabric metric far more per pound.
• You own a listed building, uPVC double glazing is usually refused; go to secondary glazing (see above).

The right order is the same across this site: cheapest points first, fabric second, and glazing only when comfort, noise or presentation justify it on its own terms. To work out how many points you actually need, start from your current rating on the homepage or check it free via the national EPC register. And for a straight answer on any measure, our FAQs cover the questions owners ask most.

Frequently asked questions

Does double glazing improve an EPC rating?

Yes, but far less than most people expect. Windows carry only around 10 to 15% of the score’s weight, and in a documented landlord case £5,400 of new front-elevation double glazing added exactly +2 points, roughly £2,700 per point, the worst value of any common measure. Fit glazing for comfort, noise, condensation and sale appeal; buy your EPC points with insulation, controls and the quick wins instead.

Is draught-proofing better value than new windows for my EPC?

For value per point, yes by a wide margin. Draught-proofing costs £30 to £250 and typically adds +1 to +3 points, roughly £30 to £150 per point, against £1,000 to £2,700 per point for whole-elevation double glazing. It also delivers much of the same draught-and-comfort benefit and improves how every other measure performs. If cold draughts are the real issue, draught-proof first.

Can I fit double glazing to a listed building for the EPC?

Usually not with uPVC, replacement uPVC windows on listed buildings are routinely refused consent. The consent-safe route is secondary glazing, which is fitted behind the existing windows and is still scored on the EPC under RdSAP 10. Where consent is refused, that refusal can itself support a registrable MEES exemption on a rented listed property. Check with your local conservation officer before ordering anything.

What evidence does the assessor need for new windows?

The FENSA or CERTASS certificate for the replacement windows is the RdSAP 10 evidence document (or a direct building-control sign-off where that route was used), along with the installation invoice and any U-value data for the units. Since 15 June 2025, RdSAP 10 measures every window individually and scores from evidence, so unevidenced glazing may be assessed on pessimistic default assumptions, keep the certificate safe.

Will the October 2026 EPC changes make windows count for more?

Not materially in the owner’s favour. The 9 March 2026 partial government response proposes four headline metrics, energy cost, fabric performance, heating system and smart readiness, via the Home Energy Model (STATUS: proposal, targeted from October 2026, not law). Windows are a modest fabric contributor either way; the reform does not turn glazing into a value measure. RdSAP 10’s window-by-window measurement, already in force, is the bigger change, and it simply scores your actual glass accurately rather than assuming it.