Listed-building consent for vacuum glazing: the Kensington & Chelsea exception

In almost every listed building in the UK, changing the glass in a window is not a decision you get to make on your own. It needs Listed Building Consent — a separate, statutory permission — and doing the work without it is a criminal offence, not a paperwork slip. There is one place in the country that has flipped that default and granted the consent in advance: the Royal Borough of Kensington and Chelsea. But before anyone builds a webpage around "no permission needed", the detail matters — and for vacuum glazing specifically, a single line of the small print does most of the work.

The rule the rest of the country lives by

Listed Building Consent (LBC) sits on top of ordinary planning permission and is governed by its own legislation. Any works that would affect a building’s special architectural or historic interest need it — and altering the historic glazing of a period window usually counts. Two things about LBC are easy to underestimate. First, no council can simply waive it: the requirement is statutory, and carrying out unauthorised works to a listed building is a criminal offence that can bring prosecution, not just a refusal. Second, it is separate from planning permission and from conservation-area rules — a single job can need one consent, both, or neither.

This is also where a lot of marketing goes wrong. Historic England publishes guidance on when slim and vacuum glazing may be acceptable in historic windows, and it is genuinely encouraging about the technology. But guidance is not permission. Every case is judged locally, at the conservation officer’s discretion, and a product being described as “heritage” or “conservation-approved” by a manufacturer means nothing in law. We go through how those conversations actually tend to go in our guide to vacuum glazing for listed buildings; the short version is that you should assume you need consent and start the conversation early.

Against that background, Kensington and Chelsea is the interesting exception.

The mechanism the Royal Borough has used is a Local Listed Building Consent Order (LLBCO). It does not — because nothing can — remove the requirement for consent. What it does is grant that consent in advance for a defined class of works, so that no individual application is needed as long as you stay strictly inside the order’s conditions. Step outside them, and you are back to a full application like everyone else.

RBKC is, as far as we can tell, the only London borough to have done this for windows. It has two relevant orders, and the difference between them is the part most summaries skip — because it decides whether your window is covered at all.

Order 1: the borough-wide Window Works order (2023–2028)

The first order was made on 18 May 2023 and runs to 17 May 2028. It applies borough-wide but to Grade II buildings only — Grade I, Grade II* and ecclesiastical buildings are excluded — and it explicitly names vacuum glazing units among the acceptable glazing.

Here is the catch that limits it more than the headline suggests: it only covers windows that are already replacements. That means a window installed after the building was listed, with the benefit of listed building consent, or one that sits in a post-listing extension. Original historic sashes are not covered. So the order that names vacuum glazing is, in practice, for updating comparatively modern windows — not for the Georgian or Victorian sash most people are actually trying to keep.

Where it does apply, the conditions are tight: the window must be timber and hand-painted; the design and glazing-bar profile must replicate the existing window; glazing bars must be integral, not applied (no stuck-on bars over a single pane); the sealed units must be no thicker than 20 mm; the spacer bar must be coloured to match the frame paint; there must be no tinted glass; and the Council must be notified in writing within 28 days of completion.

There is one broadly useful provision buried in the same order. Class A also pre-grants internal secondary glazing on any window, including original ones — provided no frames or shutter boxes are cut, no uPVC is used, and no additional draught-proofing is added. For a genuinely original window that you are not allowed to alter, discreet secondary glazing is often the one route that comes pre-approved.

Order 2: the three conservation areas where original frames are covered (2026–2031)

The second order is the more significant one, because it reaches original historic frames. Made on 20 March 2026 and running to March 2031, it covers three conservation areas: Queen’s Gate, Pembridge and Holland Park.

Within them, Grade II buildings can have machine-made float glass in one-over-one or two-over-two sashes replaced with slimline double glazing, keeping the existing frames. You first have to submit evidence to the Council that the existing glass is not historic hand-blown glass — there is no fee, and if the conditions are met, no further action is needed.

This is where anyone specifying vacuum glazing has to stop and read. Condition (d) of the order requires the new panes to be 12–16 mm thick. The mainstream vacuum units are far slimmer than that: Fineo and LandVac come in at roughly 7.7 mm and 8.3 mm respectively — below the 12 mm floor. A true vacuum unit therefore arguably does not comply with this order as written, because the order is drafted around conventional slimline double-glazed units, not vacuum glass. Anything outside the conditions — a different glazing type, or replacing the frame rather than just the glass — needs an individual LBC application.

The remaining conditions reinforce the traditional-detailing intent: no silicone or mastic (a putty-style product only, bedded over a primed rebate); the spacer coloured to the frame with only its top edge visible; clear, low-reflectivity glass; and glass that is flat or hand-drawn.

And the planning side: the Local Development Order

Listed Building Consent is only half the picture. Separately, RBKC also has a Local Development Order for windows, which deals with the planning-permission side of slimline double-glazing replacements borough-wide. LBC and planning permission are distinct consents with distinct rules; the LDO handles the planning half, while the two LLBCOs handle the listed-building half. It is entirely possible to be covered by one and not the other, which is another reason to check both before assuming a job is “permission-free”.

Everywhere else, it is a full application

Step outside the Royal Borough and the picture reverts to the national norm. In Westminster, Camden, Islington, Lambeth, Hackney, Southwark and the rest, vacuum glazing in a listed building still needs a full LBC application, assessed case by case. Several boroughs also layer Article 4 directions over their conservation areas, stripping out the permitted-development rights you might otherwise have leaned on even for unlisted properties.

So the honest position — the one worth putting on a website — is narrow: “no permission needed” is only true in Kensington & Chelsea, only for Grade II buildings, and only within those specific classes of work. Any claim broader than that is wrong, and for listed-building work “we thought it was fine” is not a defence.

What this means if you are specifying vacuum glazing

Pulling it together, even in the one borough that has pre-granted consent, a genuine vacuum unit often will not fit the pre-granted classes:

In the three conservation areas covered by the 2026 order, the 12–16 mm thickness rule is written for thicker slimline DGUs, and slim vacuum glass sits below it — so a VIG retrofit into an original frame there likely still needs an individual LBC, or you use a compliant slimline unit instead.
The borough-wide 2023 order does name vacuum glazing, but only for windows that are already consented replacements, not original sashes.
Secondary glazing (Class A of the 2023 order) is the most broadly pre-approved route for original windows, and it keeps the historic glass untouched.
Everywhere else, plan and budget for an LBC application from the outset, talk to the conservation officer early, and never treat Historic England guidance — or a product’s “heritage” branding — as approval.

None of this makes vacuum glazing a bad choice for a listed home; it remains one of the few ways to get modern warmth while keeping an original window. It just means the consent route is a real line item, not an afterthought — one worth pricing alongside the glass itself in our UK cost guide, and worth reading the actual order text for before you rely on it.

This article is general information, not planning or legal advice. Local orders are amended, expire and are renewed; always check the current order text on the Royal Borough of Kensington and Chelsea’s own planning pages, and confirm your specific case with the conservation officer before starting work.