Part L 2026 and the Future Homes Standard:
A Stage-by-Stage Guide for Developers
The Future Homes Standard is no longer a future problem. With Part L 2026 confirmed and coming into force on 24 March 2027 (24 September 2027 for higher-risk buildings), the question for most development teams has shifted from “what is it?” to “what does it actually change about how we design and deliver a scheme?”
That second question is the one that matters on a live pipeline. The Future Homes Standard doesn’t just raise a compliance bar, it moves several decisions that used to happen late in the design process (heating strategy, PV sizing, airtightness detailing) much further forward, because under the new rules they can’t be traded off against each other the way they sometimes could under current Part L. Get the sequencing wrong and you end up redesigning at technical design stage, or worse, on site.
Below is how the standard changes each stage of a typical project, and where the decisions actually need to be made.
What’s changing, in practical terms
Three shifts sit behind most of the design and cost implications:
Heat pumps become the practical default for space heating and hot water, gas and oil systems cannot realistically meet the new carbon targets, so heating strategy is no longer a “value engineering” decision to defer.
On-site solar PV moves from optional to a functional requirement, typically sized around 40% of ground floor area. It has to be considered as part of the massing and roof design, not bolted on afterwards.
Fabric performance and airtightness both tighten considerably, which in most homes means mechanical ventilation with heat recovery (MVHR) becomes standard rather than a premium add-on. Overall, dwellings need to show roughly a 75–80% reduction in regulated carbon emissions against the 2013 Part L baseline, with the exact figure varying by dwelling type and form factor.
None of this is exotic. But each one has knock-on effects for layout, MEP servicing zones, procurement and programme, which is why the timing of the energy strategy matters more than it used to.
Concept and feasibility: where the real decisions get made
Under the current standard, energy strategy has often been treated as a compliance exercise that follows the design. Under the Future Homes Standard, that ordering causes problems. Heat pump plant needs space (and often external siting) that affects layout; PV sizing affects roof form and orientation; airtightness targets affect the detailing of junctions that get fixed once a design is signed off.
Planning stage: the standard you design to isn’t optional anymore
Local planning policy has, in many authorities, been ahead of national Part L requirements for a while. What changes now is that the national baseline catches up, so the energy strategy submitted at planning needs to reflect Future Homes Standard performance, not the outgoing standard, for any scheme that won’t have building control submissions in before 24 March 2027.
That transitional date matters and is worth getting right: only a full plans application, building notice, or initial notice submitted before that date protects a scheme under current rules, and even then, each individual dwelling still has to show construction genuinely commenced (foundations, any basement, and ground floor structure complete) before 24 March 2028. Groundworks, demolition and site clearance don’t count. Assuming a scheme is “covered” because outline consent predates the standard is one of the more common and costly misreadings developers make.
Technical design: where compliance methodology changes underneath you
Compliance modelling is also shifting from SAP 10.3 to the new Home Energy Model (HEM), with a dual-running period while the industry transitions. For technical design teams, that means the modelling approach used at planning stage may not be the one used to discharge conditions or satisfy building control later in the same project, worth confirming early with your energy consultant rather than assuming continuity.
This stage is also where the “no terrace averaging” principle bites: each dwelling has to meet requirements individually, so a scheme mix that relied on stronger-performing units offsetting weaker ones under the old approach needs re-checking unit by unit.
What this means for programme and cost
The honest summary: schemes that treat energy strategy as an early-stage design input, rather than a late-stage compliance document, tend to absorb the Future Homes Standard with far less disruption and cost. Schemes that don’t tend to face one of two outcomes, a redesign once heat pump plant or PV requirements are discovered late, or a retrofit-style upgrade after the fact, which is consistently more expensive than designing it in from the start.
