Understanding Part L and the Future Homes Standard A Guide by Façade Creations

Introduction

The government has now published its response to the Future Homes Standard consultation, giving the industry a clear view of the performance requirements new-build homes will need to meet from 2027. For aluminium systems, this update brings welcome clarity: the notional U-Value for windows has been set at 1.2 W/m²K, avoiding the previously feared 0.8 W/m²K and striking a more practical balance between efficiency and cost.

From 2027, U-Values must be calculated using the actual size and configuration of each window – not the traditional standard test size. The rules also widen the scope of what must be included in these calculations, from cills and couplers to add-ons, raising the technical bar for fabricators, installers, and specifiers alike.

At Façade Creations, our estimating software already calculates whole-window U-Values, with all frame data validated by third-party Notified Bodies. We are scheduling our product simulations now so that both we and our customers are fully prepared well ahead of when the Future Homes Standard comes into force. We hope this guide is useful, and our team is on hand to support you through the transition.

Documentation needed

Installers will need to provide:

• Configuration-specific U-Value calculations using actual sizes
• All product specifications used in the thermal model
• Photographic evidence showing insulation and airtightness measures around openings before they are covered
• Installation photos referenced in the BREL report

Installers must also give homeowners operation and maintenance information within five days of completion.

Replacement, refurbishment & extensions

Replacement windows/doors

The U-Value of replacement windows and doors in existing dwellings should be no higher than that of the element being replaced, and must meet the limiting standards set out above. All replacement units must:

• Meet the relevant limiting U-Values (1.4 W/m²K for windows)
• Be reasonably draught-proof
• Not worsen the thermal performance of the element being replaced

Extensions

New windows and doors installed into extensions must meet the same limiting values as any other new element.

What this means for specifiers and fabricators

• Project-specific U-Values are required – not generic system values
• All add-ons, couplers, and bars must be included in performance calculations
• Early coordination with installers is essential to ensure airtightness and thermal requirements can be met on site
• Calculations should be aligned with Part O (overheating) and Part F (ventilation)

Installers and fabricators must also be able to demonstrate appropriate skills, knowledge, and experience; the ability to provide compliant workmanship and documentation; and Competent Person Scheme registration where self-certifying.

Extensions

New windows and doors installed into extensions must meet the same limiting values as any other new element.

What this means for specifiers and fabricators

• Project-specific U-Values are required – not generic system values
• All add-ons, couplers, and bars must be included in performance calculations
• Early coordination with installers is essential to ensure airtightness and thermal requirements can be met on site
• Calculations should be aligned with Part O (overheating) and Part F (ventilation)

Installers and fabricators must also be able to demonstrate appropriate skills, knowledge, and experience; the ability to provide compliant workmanship and documentation; and Competent Person Scheme registration where self-certifying.

WER / DSER ratings

The Window Energy Rating (WER) / Door Set Energy Rating (DSER) system rates products on a scale from E to A++, with A++ being the most energy efficient – similar in concept to the energy labels seen on household appliances such as fridges. WER/DSER can be used as a compliance method, but only for existing dwellings and “domestic type windows” on other buildings.

Timeline: how we got here

• 15 December 2021 – Government publishes new interim Part L, Part F, and Overheating Regulations for domestic and non-domestic buildings, ahead of the Future Homes and Buildings Standard.
• June 2022 – Interim Part L, Part F, and Overheating Regulations come into effect. Developers needed to submit a building notice, initial notice, or deposit plans by this date for transitional arrangements to apply, provided work started before 15 June 2023.
• Autumn 2021 – Summer 2022 – Research and analysis to develop the proposed technical specification, alongside ongoing industry engagement (including through BRAC and technical working groups).
• Summer 2022 – 2024 – Development of sector-specific guidance to embed understanding of the Future Homes Standard’s technical specification.
• Spring 2023 – Technical consultation on the proposed specification for the Future Homes Standard.
• 2024 – Part L FHS Regulations made and brought into effect.

The interim Part L changes from June 2022 were the first of two phases designed to drive improved thermal efficiency in new buildings, and the full Future Homes Standard builds on that foundation from 2027. Overall, the changes aim to deliver a 30% reduction in carbon emissions from new homes and a 27% reduction from other building types. Alongside Part L, there are also changes to Approved Document F (covering trickle vents) and an entirely new Approved Document O, which addresses glazing and overheating.

It’s important for specifiers, fabricators, and installers to review specifications made in 2022 and understand what transitional arrangements may apply to projects set after June 2022.

How Façade Creations can help

Our team supports fabricators, specifiers, and installers navigating these changes by:

• Providing validated U-Values, thermal bridging data, and full configuration U-Value support
• Ensuring all profiles and accessories are thermally modelled to 2027 requirements
• Offering fabrication guidance for fully compliant solutions
• Remaining transparent about how our products perform
• Offering project-specific thermal modelling
• Supporting compliant specification across new build, retrofit, and extension projects

Façade Threshold

Ground Floor Treatments

A versatile and flexible solution for a range of applications - including shop fronts, entrances, and ground floor framing - the Façade Threshold aluminium ground floor treatment system has been designed to deliver high levels of performance through thermally broken screening. The system also includes an integrated range of high-traffic, anti-finger trap doors suitable for single storey applications.

Built for high thermal performance, the Façade Threshold aluminium ground floor treatment system uses a ladder frame construction, offering a flexible solution for low-rise glazing applications and integrating seamlessly with our other systems. It accommodates sealed units from 6mm up to 32mm, improving both thermal and acoustic performance.

The Façade Threshold system achieves U-values of 1.7 Uw with double glazing and 1.5 Uw with triple glazing.

Design features

• Pocket or bead glazed for ease of on-site glazing
• 110mm frame depth to accommodate a range of applications
• Slim 55mm profile width for increased glazing and light transmission
• Ladder frame construction for fast on-site installation
• Fully compatible with other systems in the range

Options

• Accommodates 6mm - 32mm sealed units for improved thermal and acoustic performance
• Wide range of hardware available for full customisation
• Available in single or dual colour options, with polyester powder coating and anodised finishes

Aluprof’s fire rated products