Designing for Part L: Why Screed Specification Is Now Critical for Future Homes Compliance

The UK’s Future Homes Standard marks a decisive shift in how homes are designed, built, and heated. With Part L (Energy) driving a 75–80% reduction in carbon emissions compared to 2013 standards, architects are now working within a fundamentally different design framework: one where every component of the building fabric must actively contribute to performance.

Whilst most of the energy efficiency transition has focused on heat pumps and insulation, floor construction, and specifically screed specification, has become a critical factor in achieving compliance.

The Proliferation of Heat Pumps and What It Means for Floors

Part L is accelerating the transition away from gas boilers towards low-carbon, low-temperature heating systems, primarily heat pumps. These systems operate most efficiently at low temperatures of 30–50°C, which fundamentally changes how heat is delivered within a building. Traditional radiators can struggle at these lower temperatures especially with heat pumps. Underfloor heating systems (UFH) deliver even heat distribution at low temperatures and can be ~25% more efficient than radiators in some cases. This is why heat pump specification typically goes with UFH. As a result, underfloor heating is rapidly switching from a luxury upgrade to a default design solution.

Heat pumps work well with high insulation strategies, but designing for reduced floor build-ups with UFH and insulation integration into the building’s fabric requires coordination which is harder, but not impossible to install after the initial design. For architects, this means specifying UFH early (at stages 2-3 of RIBA’s Plan of Works) and aligning with M&E engineers to ensure insulation compatibility, airtightness and fire compartmentalisation are achieved. Last, but not least, the specified screeds must be selected to match the underfloor heating system’s requirements, since the floor screed is the radiator of heat and plays a major part in the energy efficiency of the system. In combination with UFH, screeds can optimise system performance, such as speed of heat up and, the ability to demonstrate the desired load distribution capabilities, and point load resistance required. They can provide extra airtightness in the building as well. Floors are no longer passive design elements, but active components of the building’s energy system.

Underfloor Heating Performance Starts with the Screed

UFH performance is heavily dependent on how effectively heat is transferred from the pipework into the occupied space. This is where screed selection is essential to optimal performance. Anhydrite screeds outperform traditional options by providing faster, more efficient heat transfer thanks to their naturally higher thermal conductivity. Self-levelling liquid screeds, such as those in the Gyvlon range optimise UFH performance by encapsulating the pipes fully and eliminating air voids. Their higher thermal conductivity maximises UFH systems’ output by radiating more heat for the same input temperature, allowing for lower degrees to achieve the same output into the room, making them ideal for wet or dry systems. In fact, the Gyvlon ThermioMAX® FD E2C (fast drying, early to cover) screeds are designed to be the most efficient heat transmitter available on the market, as guaranteed by the BBA. It is the only screed complying with the BS1264 heating standard, specifically for application with underfloor heating or cooling systems. This results in long-term energy cost savings, which can be especially prominent when underfloor heating is combined with air source heat pumps.

Compared to traditional sand–cement screeds, which are typically thicker and slower to respond, flowing anhydrite screeds are inherently aligned with low-temperature heating strategies. The benefits also transfer to the building occupants long-term, as faster heat up times at lower temperatures mean greater comfort and environment to live in, at lower energy costs. Your UFH can now heat and cool your rooms giving you comfortable living spaces and peace of mind with the ever-rising heating bills.

Fabric-First Design Is Changing Floor Build-Ups

To meet Part L energy targets, architects are adopting a fabric-first approach, prioritising, higher insulation levels, improved airtightness, and reduced heat loss through the building envelope. This means specifying thicker insulation layers as standard, requiring screeds that can perform reliably over compressible insulation. In addition, floor build-ups must be optimised for both structure and thermal efficiency. Gyvlon’s full range of screeds are engineered specifically for this reality, complementing all types of floor construction - wood, beam, block, concrete and steel decking, invariably delivering thinner screed cross sections than traditional screeds.

As insulation thickness increases, so does the need for screeds that can manage load distribution and deflection at thinner cross section. Gyvlon’s solutions address this with excellent load-spreading capability and high compressive strength, especially the reinforced Gyvlon XTR screeds, designed for heavy foot fall and point loads, resisting cracking over flexible substrates. This allows for higher insulation thickness in combination with thinner screeds to achieve the recommended U-value without changing the building design.

Gyvlon ECO® Screeds - Designed for Modern Floor Construction

Gyvlon ECO® Screeds are purpose-built for floating (over insulation and membrane) and unbonded (over a membrane) applications, making it fully compatible with airtight membranes, damp proof membranes (DPMs), thermal and acoustic insulation systems. Its free-flowing, self-compacting formula requires no mechanical fixings, allowing for more design freedom. Its installation is consistent, void-free, and protective of airtight junctions.

 

Thin Section Performance for Faster Response

One of the most important advantages for architects is the ability to design reduced floor build-ups without compromising performance. Gyvlon screeds can be installed in significantly thinner sections than traditional screeds. Systems such as Gyvlon ThermioMAX® FD E2C can be installed from as little as 15mm floating and 10mm bonded above UFH pipes. This delivers faster heat response times, improved system efficiency, and greater design flexibility in constrained build-ups in retrofitting and refurbishment projects.

Supporting Airtightness and Junction Detailing

With tighter airtightness targets under the Future Homes Standard, junction detailing is now critical, especially at floor-to-wall interfaces. Gyvlon screeds support this by integrating seamlessly with edge strip systems, maintaining insulation continuity, and applying without disturbing airtight membranes.

The result is a floor system that contributes to, rather than compromises, the building’s airtightness strategy.

A New Role for Architects: Designing Floors Earlier

One of the biggest shifts driven by Part L is when floor systems are considered. Specifying underfloor heating and screed during the Concept and Developed Design stages enables architects to optimise floor build-ups, coordinate insulation, structure and services, ensuring compliance with SAP and Home Energy Model targets.

Floor specifications are no longer guided by rules of thumb, but driven by energy modelling, considering the entire system. Screeds must be compatible with insulation, UFH system specifications, floor finishes, and airtightness strategy, so they can no longer specified in isolation.

The Shift Away from Traditional Screeds

Whilst regulations do not explicitly mandate screed types, the direction of travel is clear.

Traditional sand-cement screeds require greater thickness, offer lower thermal performance, and respond more slowly to heat input, whilst anhydrite flowing screeds are more thermally efficient and better suited to thicker insulation and low-temperature heating systems, enabling a fabric-first approach to methods of construction. Against the changes to the Future Homes Standard, screed is a compliance-critical part of the flooring system.

Gyvlon screeds provide solutions that are fully aligned with UK’s amplified drive to home energy efficiency by supporting low-carbon design, optimising high-performance UFH integrations, and complementing seamlessly fabric-first construction. In the context of Part L, the question is no longer “which screed?,” but whether your screed is actively helping you meet compliance.