Marketing for window and door installers
This is one of the few home improvement trades with a real compliance certificate a homeowner can look up. It is also a trade where the published prices disagree by four times on a single window. This page covers how to use the first and survive the second.
FINDING
Checkatrade was cited in 50 of the 60 Google AI Mode answers Whito collected for electricians, plumbers and roofers across 20 UK towns on 22 August 2026, 83%, while only 9% of UK homeowners rate a builder’s website among their top three factors.
Source: UK trades marketing statistics, Whito Research.
What we know, and what we have not measured yet
Whito has not yet run an AI visibility study on glazing firms. The figures above come from cross-industry trades work in August 2026, and from a day of reading scheme, council and cost guide pages at source on 8 September 2026.
One gap is not ours and is worth stating plainly. Nobody knows how many registered window installers there are in the UK. The most recent per-scheme counts we could obtain are the government’s competent person scheme statistics for 1 October 2017 to 31 March 2018, which recorded 6,051 FENSA members and 2,107 Certass members. Neither scheme publishes a current figure. Anyone stating a 2026 installer count is either citing that eight-year-old dataset without saying so, or has made it up.
When the glazing engine study runs it lands on this page first, including the question nobody has published: of the installers an AI engine recommends in a given town, how many show a scheme registration a homeowner could check. Until then the AI Visibility Index shows the method across eight other sectors.
Whito need-to-know for glazing firms
- It is not a FENSA and Certass duopoly, and that matters commercially. The government’s authoritative list of competent person schemes, read on 8 September 2026, shows six operators authorised for replacement windows and doors: Blue Flame Certification, Certass, Certsure trading as NICEIC, FENSA, NAPIT and Assure. ELECSA is not on the current list. If you are renewing without shopping around, you have four more options than you thought.
- There is no such thing as a FENSA certificate, according to Certass. FENSA sells homeowners a copy of “a FENSA certificate” for £30 including VAT. Certass publishes that there is no such thing, only a Building Regulations Compliance Certificate, which multiple schemes can issue and which serves the same purpose. Both positions are published by the parties themselves. The commercial effect is that a Certass-registered installer loses jobs to a vocabulary problem rather than a compliance one, which is a positioning fix, not a certification one.
- Registration is a fixed cost that punishes low volume. FENSA publishes its own worked examples: about £337.75 a year at 10 installations, £667.50 at 100 and £1,222.75 at 300, all excluding VAT, on top of a one-off application of £267.40. That is roughly £34 a job at ten jobs a year and about £4 a job at three hundred. Most should-I-join content misses that entirely.
- A national cost guide is quoting your certificate cost at ten times its price. Checkatrade’s window fitting guide states a FENSA certificate adds £25 per window. FENSA’s own published fee schedule, document FSPF 53 issue 9 dated January 2025, puts the notification fee at £2.05 excluding VAT per installation, not per window. That is the most concretely checkable pricing error we found in any consumer guide, and it is being used against you in quote conversations.
- Part Q does not apply to replacement windows. Approved Document Q, 2015 edition, applies to new dwellings only. An installer marketing a replacement window as Part Q compliant, as required by law, is describing an obligation that does not bind that job. Selling on a rule that does not apply is a bad position to be caught in.
- The 2027 Part L change does not change replacement window U-values. The 2026 edition of Approved Document L takes effect on 24 March 2027 for non-higher-risk work, and it keeps the same replacement figures: 1.4 or Window Energy Rating band B for windows, doorset band C for doors over 60% glazed and band B for others. Anyone selling beat the 2027 regulation change on replacement window U-values is selling a change that does not exist.
Why glazing firms lose good jobs
Beaten by a brand name, not a standard
Homeowners, estate agents and conveyancers ask for a FENSA certificate by name. A Certass-registered installer issues an equally valid Building Regulations Compliance Certificate and loses the job to a word.
Quoting against guides four times apart
For essentially the same uPVC casement, MyBuilder publishes £160 to £250 and Checkatrade £500 to £1,250. On a three-bed rewindow the ranges do not overlap at all: Checkatrade’s floor of £8,000 is above MyJobQuote’s ceiling of £6,000.
Nothing that survives a conveyancing search
The certificate is the thing that turns up years later when the house sells. An installer who explains that, and who logs the notification properly, is selling something a cheaper quote is not.
What actually works
In this order. Structure before scale.
Name your scheme and what it issues
Which of the six authorised schemes you are registered with, your registration number, and one plain sentence saying the certificate is a Building Regulations Compliance Certificate whichever scheme issues it.
Explain what happens if the installer is not registered
The homeowner has to apply for regularisation themselves. Published council charges for that vary enormously, and the homeowner pays whether or not the work turns out to comply. That is the case for using you, told honestly.
Publish a per-window price and a worked house
One casement, supply and fit, and one three-bed house with the window count, the scaffolding, the waste and the making good. It settles a conversation the guides have made impossible.
Correct the certificate cost on your own page
Say what the notification actually costs and that it is per installation, not per window. It is a small, checkable, generous correction and it makes everything else you say more credible.
Be accurate about Part L and Part Q
Do not sell a 2027 change that does not apply to replacements, and do not claim Part Q on a retrofit. Being the firm that gets the rules right is a real position when three competitors are getting them wrong.
Reviews that name the property and the job
Nine windows and a composite door on a 1930s semi in Beeston, three days. Searchable, quotable, and it tells the next customer their house is one you have done before.
Quick wins this week
Put your scheme registration number on the site
As text, with the scheme named and a link. It is the one checkable credential this trade has and a surprising number of installers bury it in a logo image.
Write the resale paragraph
Two hundred words on what the certificate is, when it matters, and what the homeowner does if they lose it. Free, and it is the single most useful thing on most glazing websites.
Publish one worked house
Window count, product, scaffolding, waste, making good, days on site and total. One evening, and it beats four national averages that contradict each other.
Common mistakes
Selling a 2027 regulation change on U-values
The 2026 edition of Approved Document L takes effect in March 2027 and keeps the same replacement window standard. Selling urgency on a change that is not happening is the kind of claim that gets a firm reported.
Claiming Part Q on replacement windows
Part Q applies to new dwellings only. Quoting it on a retrofit is either a mistake or a pressure tactic, and a well-briefed customer will know.
Letting the customer believe only FENSA counts
Six schemes are authorised for windows and doors. If you are in one of the other five, say so clearly and explain the certificate is the same. Silence loses the job.
Window and door marketing guides
Six authorised schemes, one legal document, a £30 replacement fee and a dispute between two schemes about what to call it.
Free marketing for an installerThe records that must agree, the resale paragraph nobody writes, and a weekend of fixes that cost nothing.
The prices disagree by four timesWhat Checkatrade, MyBuilder and MyJobQuote publish, where they conflict, and the certificate cost one of them has wrong by ten times.
Window software, and who publishes a priceVertical systems at £120 to £500 a month, general trade apps at £28, and two industry names that publish nothing at all.
The register that matters
This trade has a certificate a homeowner can look up. Use it.
Replacing windows and doors is work that needs Building Regulations approval, and GOV.UK sets out three routes: a local authority building control application, a private registered building control approver, or an installer registered with a competent person scheme who self-certifies. That third route is the one the trade runs on, and the government’s authoritative list, read on 8 September 2026, names six operators authorised for replacement windows and doors: Blue Flame Certification, Certass, Certsure trading as NICEIC, FENSA, NAPIT and Assure. FENSA publishes its fees in full: £267.40 to join, £172 a year excluding VAT, and £2.05 excluding VAT per installation notified, with its own worked examples putting total annual cost at about £337.75 at ten installations and £1,222.75 at three hundred. Certass publishes a £120 initial company audit fee and does not publish a monthly rate. What the certificate proves is compliance, and the argument worth making to a customer is what happens without it: the homeowner, not the installer, has to apply for retrospective regularisation, and the published cost of that varies enormously. Lancaster City Council charges £126 including VAT for fewer than ten windows with regularisation at 150% of the net charge, about £189. The London Borough of Lambeth charges £476.05 for the same retrospective job. Lambeth also publishes that there is no entitlement to a refund even if it cannot certify the work. All read at source on 8 September 2026.
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Looking for an installer instead?
Whito is a marketing guide for the trade, not a booking site. If you are trying to hire, the Whito directory lists verified UK businesses, and every listing is checked against the public record before it appears.
Whito is independent and companies cannot pay to appear in our guidance. This page is marketing advice, not building control advice: check scheme requirements with the scheme itself and regularisation charges with the relevant local authority, because they vary and they change.