Bradley Hirst of Knauf Insulation explains why designers must uplift thermal standards ahead of the Future Homes Standard, in order to futureproof homes.

The Future Homes Standard (FHS) is still working its way through consultation at the time of writing, but the fundamentals are clear. New homes will need to produce 75 to 80% lower carbon emissions than those built under 2013 regulations, with an expectation that low-carbon heating and higher fabric performance become the norm. Although the timeline for implementation has been delayed several times, many architects and housebuilders are already changing their approach to the way homes are designed.

For architects, the most useful way to think about “building ahead” is not by chasing a single notional target, but by focusing on delivering real thermal performance that stands up to increased scrutiny and prepares homes for low and zero carbon (LZC) technologies.

What we know about the FHS

In England, the 2022 uplift to Building Regulations, through Part L and Part F, was designed as a stepping stone towards the FHS, tightening limiting U-values and raising expectations on ventilation. Part O was also introduced, making overheating mitigation a new but essential consideration for residential design.

A central part of how future compliance will be demonstrated is through comparison with a notional dwelling. There are two proposed specification options: one that maximises carbon savings through measures such as solar PV, decentralised ventilation and wastewater heat recovery, and a second, leaner route that uses fewer technologies but still delivers at least 75% carbon savings compared with 2013 regulations.

In both cases, the actual dwelling must meet or outperform the notional benchmark in key metrics such as primary energy use and carbon emissions when assessed using the new Home Energy Model.

The Home Energy Model (HEM) will replace SAP as the methodology underpinning regulatory compliance. While modernising the structure of the model should make it more flexible and easier to use, the implications for building design are significant. Energy use will be more accurately simulated and assessed, placing greater emphasis on closing the gap between design intent and as-built performance.

Fabric first is the key to LZC

Solar PV, heat pumps and mechanical ventilation with heat recovery (MVHR) often dominate the conversation around future homes. While the exact requirements for these technologies are still being confirmed, they are expected to play a central role in meeting future carbon targets. Their effectiveness, however, depends on a well-insulated building envelope, combined with controlled ventilation and sufficient airtightness.

Heat pumps, for example, must be correctly sized for the spaces they serve. If excessive heat is lost through the building fabric, the effective heating demand increases, reducing efficiency and undermining performance even where the system has been correctly specified. The lower the space heating demand, the smaller and more efficient the low-carbon heating system can be, and the easier it becomes to avoid high peak loads and uncomfortable temperature swings.

This makes an efficient building fabric essential to the goal of reducing overall energy consumption that LZC technologies are designed to achieve.

Building ahead

Taking a fabric first approach to home design means considering how material choice affects as-built performance, and where standard practices may need to change to ensure thermal efficiency.

Loft insulation is a good example. It is highly cost effective, relatively simple to install, and has a substantial impact on thermal performance. Many architects are already specifying insulation depths well beyond the current minimum of 270 mm, with some designs accommodating up to 500 mm. This maximises roof performance and provides flexibility elsewhere in the overall energy strategy.

Change is also evident in cavity wall design. Despite a modest increase in building footprint, 150 mm cavities make it easier to achieve lower U-values using full-fill insulation such as glass mineral wool. Wider cavities reduce thermal transmittance and allow the use of insulation that is more tolerant of site conditions and less prone to air gaps, helping to deliver consistent thermal performance in practice.

Making homes ready

Honey, founded in 2022, is one example of a housebuilder deliberately working ahead of the incoming standard by focusing on buildability and measurable outcomes.

At Thoresby Vale in Nottinghamshire, Honey has delivered homes designed to exceed the likely direction of FHS targets. The specification includes fully filled 150 mm cavities, upgraded party wall insulation to prevent thermal bypass, and loft insulation installed to a depth of 500 mm, thereby achieving a reported roof U-value of 0.09 W/m²K.

One early completion achieved an EPC A rating with a score of 92, air permeability of 3.9 m³/h.m², and operational CO₂ emissions of 1.4 tonnes per year, compared with a UK average of around six.

The future is stricter, but also more testable

Standards are tightening because outcomes matter: running costs, health, comfort and national carbon targets. With more detailed and nuanced assessments available through the Home Energy Model, understanding of how to close the performance gap should continue to improve.

Building ahead of the FHS means getting the fabric right first, enabling low and zero carbon technologies and delivering real thermal efficiency in new homes.

Bradley Hirst is technical services manager at Knauf Insulation