Double-Glazing Windows in Listed Buildings: RBKC New Order Explained.

The Royal Borough of Kensington and Chelsea has introduced a "Local Listed Building Consent Order" (LLBCO) for Grade II listed buildings to streamline permissions for specific window works. This follows a similar LLBCO passed last year, allowing for the installation of solar panels on listed buildings. Here's a summary of its key points:

What’s the point of an LLBO Order?

- Facilitate energy efficiency upgrades (e.g., window modifications) while safeguarding the architectural and historic integrity of listed buildings.

- Support the borough's carbon neutrality goals, set for 2040.

Who can benefit from this LLBCO?

Applies to Grade II listed buildings in the borough, but excludes:

- Grade I and Grade II* listed buildings

- Buildings used for ecclesiastical purposes

What Works Can I Do Without Listed Building Consent?

- Secondary Glazing (Class A): Installation of interior secondary glazing to windows with minimal visibility and no alterations to the existing structure.

- Window Replacement (Classes B and C): Replacement of windows, fanlights, or external doors in non-original extensions or post-listing additions using double or vacuum glazing, adhering to strict design and material specifications.

Are There Any Conditions?

- Maintain historic elements such as frames, cells, and casings.

- Use timber with hand-painted finishes and prohibit UPVC.

- Ensure double-glazing thickness does not exceed 20mm.

- Notify the council upon completion of works.

The order reflects advancements in double-glazing technology. Modern slimline double-glazing options, often as thin as 11mm, can be integrated into heritage-appropriate timber frames or even inserted within existing historic frames, minimizing visual impact.

Why the Change?

- Recognizes windows as critical historical and architectural features.

- Balances energy efficiency with preservation of heritage.

- Double glazing allowed only where original historic windows are absent or beyond repair.

When Will These Changes Apply?

- LLBCO runs from May 18, 2023, to May 17, 2028, with annual reviews.

- May be revoked or renewed depending on its effectiveness and impact.

Who Benefits?

- The Environment - Reduces carbon emissions while maintaining heritage aesthetics.

- The Public - Simplifies processes for residents seeking to improve energy efficiency.

High-profile examples, such as the solar panels on King's College Chapel and the double-glazed windows at Ledston Hall, demonstrate that with careful planning and expert guidance, sustainable technologies can be successfully integrated into historic buildings.

Notes:

Overview of Listing Grades:

- Grade I: Buildings of exceptional interest, making up about 2.5% of listed buildings (e.g., historic cathedrals or castles).

- Grade II*: Buildings of particular importance, warranting more protection than standard Grade II buildings. Around 5.5% of listed buildings fall into this category.

- Grade II: Buildings of special interest, forming the majority (approximately 92%) of listed buildings.

If you own a Grade II* property, consult with your local planning authority before undertaking any work, even minor changes.