There’s a conversation I’ve had more times than I can count. A client walks into the first project meeting, slides a brief across the table, and says the words with complete confidence: “We want a net zero building.” And I nod, knowing that before we can even open a laptop, we need to have a much longer conversation about what that actually means — because in 2026, “net zero” can mean almost anything, depending on who’s asking.
The Gap Nobody Talks About
Most clients commissioning “net zero buildings” today are, if I’m honest, buying something significantly less ambitious than they believe. The gap between marketing language and technical compliance is wide — and getting wider as more frameworks compete for the same label.
Before a single line gets drawn, there’s a policy and standards question that needs to be resolved. In the UK, new buildings are subject to Part L of the Building Regulations, which governs energy efficiency, and increasingly clients face additional requirements from local planning authorities — particularly in London, where the GLA’s energy hierarchy means projects must demonstrate reductions in both regulated and unregulated carbon as part of the planning process. ESG investor frameworks, corporate sustainability commitments, and pre-let requirements from major occupiers are adding further layers. The result is that a client saying “net zero” might mean compliance with Building Regulations, or a board-level ESG pledge, or an actual science-based technical standard — and each of those is a very different project.
Not All Frameworks Are Equal — And the UK/US Gap Is Wider Than You Think
Three frameworks shape the UK professional conversation most directly. But for firms operating across both markets — or considering expansion into the US or Europe — the contrast with American standards is just as important to understand. The table below is deliberately structured as a cross-market reference tool, because the gaps between UK and US approaches are significant enough to affect project scope, fee structures, and client expectations from day one.
| UKGBC / UK NZCBS | LETI Climate Emergency Design Guide | RIBA 2030 Climate Challenge | LEED v5 (US) | ASHRAE 228 (US) | |
| Geographic scope | UK | UK / International voluntary | UK (RIBA Chartered Practices) | Global (126+ countries) | US primary; international applicable |
| Primary focus | Operational carbon; whole life carbon pathway | Whole life carbon: operational + embodied | Operational energy, embodied carbon, potable water | Decarbonisation, quality of life, ecological resilience | Operational zero net energy / zero net carbon only |
| Embodied carbon | Mandatory disclosure + limits (UK NZCBS pilot) | Mandatory — central to framework | Mandatory — LETI-aligned targets | Required assessment (A1–A3); reduction credits available | Not covered — operational scope only |
| Unregulated energy | Included in UK NZCBS | Fully included | Fully included | Included via whole-building metering | Included (source energy calculation) |
| Offsetting | Last resort; “Aligned Plus Offsets” designation | Strongly discouraged | Permitted after reduction hierarchy | Credits available; not a requirement | Permitted for sites lacking on-site renewables |
| Electrification mandate | Encouraged; required in UK NZCBS for new builds | Yes — heat decarbonisation is a core pillar | Yes — fossil fuel phase-out expected | Mandatory for LEED Platinum (full electrification required) | Not mandated; fuel-neutral carbon calculation |
| Renewable energy | Required to reduce offset reliance | On-site and grid-sourced | On-site and grid-sourced | Required for Platinum; credits for others | Onsite or offsite (with strict REC retirement rules) |
| Verification / auditing | Third-party audit required (UK NZCBS) | Self-reported; peer review | Annual data submission to RIBA | Third-party USGBC certification | Self-evaluated against standard methodology |
| Post-occupancy performance | Required (in-use data) | Required — design vs. actual gap tracked | Required — annual data submitted | Mandatory for O+M track; 3-year monitoring for Platinum | Based on measured operational data |
| Regulatory mandate | Voluntary standard (planning policy varies by LPA) | Voluntary | Voluntary | Voluntary | Voluntary — no federal mandate |
| Social equity / resilience | Limited scope | Limited scope | Limited scope | New prerequisites in v5 — central to framework | Not in scope |
| Refrigerants | Not specifically addressed | Not central | Not central | Strict: zero or ≤700 GWP required | Not in scope |
| Energy target (offices) | 75 kWh/m²/yr (2025), tightening to 2040 | EUI targets by typology; more onerous | 75 kWh/m²/yr (2025) | ASHRAE 90.1-2019/2022 baseline; 10%+ improvement required | Source EUI balance to zero |
What This Table Actually Means If You’re Crossing Markets
The differences here aren’t cosmetic — they represent genuinely different philosophies about what “net zero” means, and they have direct consequences for how you scope, price, and deliver projects.
If you’re a UK firm entering the US market: The most immediate culture shock is the absence of a mandatory embodied carbon framework at federal level. US energy codes vary significantly by state — several southern states still operate on IECC 2015, while western states like Colorado, Oregon and Nevada have adopted ASHRAE 90.1-2019 — meaning a “compliant” building in Texas and a “compliant” building in California are not remotely equivalent by UK standards. ASHRAE Standard 228 is a genuine step forward as a universal measurement framework for zero net energy and zero net carbon, but it covers operational performance only — embodied carbon, a non-negotiable pillar of LETI and UK NZCBS, remains largely unaddressed at the federal level. UK firms used to comprehensive whole-life carbon assessments from Stage 1 will find US clients often haven’t been asked for this data at all.
The good news: LEED v5, launched in April 2025, places half of all available points on carbon-related strategies — a first for the system — requiring evaluation of both embodied and operational carbon, planning for electrification, and integration of renewables. LEED v5 also now scores projects on their contribution to grid decarbonization, promoting demand flexibility and renewable energy storage. The framework is moving in the UK direction, just from a different starting point and without the regulatory backstop that UK planning policy increasingly provides.
If you’re a US firm entering the UK or European market: Prepare for the embodied carbon conversation to happen much earlier and more rigorously than you’re used to. A LEED Platinum certification — highly regarded in the US — will not impress a UK planning officer asking for a LETI-compliant whole-life carbon assessment. LEED v5 requires projects to assess and quantify embodied carbon from cradle to gate (A1–A3) for structure, enclosure, and hardscape — but UK frameworks typically expect A1–A5 (including construction process emissions) as a minimum, with A1–A5 plus operational carbon for projects targeting RIBA 2030 compliance. The measurement boundary is wider, the targets are more granular by typology, and the expectation of post-occupancy data submission is standard practice rather than an optional track.
The other significant gap is refrigerants. LEED v5 drives HVAC systems toward zero refrigerants or refrigerants with 700 GWP or less, with mandatory leak checks and pressure testing before commissioning — a requirement that aligns more closely with UK good practice than older LEED versions. But this is still a LEED-specific requirement; it isn’t embedded in LETI or RIBA 2030, meaning it’s worth raising proactively with UK MEP engineers who may not have it on their radar.
The honest summary: the US market is catching up fast, but it’s still operating on a different baseline. A building that satisfies ASHRAE 228 and achieves LEED v5 Gold is doing serious, credible work — but it may still fall short of LETI’s embodied carbon targets or the UK NZCBS operational thresholds. Firms working across both markets need to specify, explicitly and early, which framework governs each project — and resist the temptation to let a certification badge from one market substitute for genuine compliance in another.
That disambiguation conversation, uncomfortable as it sometimes is, is part of the value we bring.
The Lesson I Learned the Hard Way
Based on my own experience on projects across different scales and markets, the single most important thing we can do before pencil touches paper — or model touches screen — is sit down with the owner and go through every technical requirement and design criterion in detail. Not as a box-ticking exercise, but as a genuine conversation.
The standards and frameworks included in that early briefing document are the foundational layer of the entire design. They determine whether you’re optimizing for regulated energy or whole life carbon, whether offsetting is acceptable or a last resort, whether you’ll need a third-party audit at handover, and how you’ll measure actual in-use performance years later. Getting that wrong at RIBA Stage 0 or 1 is recoverable — getting it wrong at Stage 4 means retrofitting ambition onto a design that was never structured to deliver it, which almost always ends in expensive offsetting rather than genuine performance.
And here’s the uncomfortable truth: owners don’t always know what they’re asking for. The phrase “net zero” has become a shorthand for “environmentally responsible,” which is a perfectly valid aspiration. Our job is to translate that aspiration into a technically precise scope — and to explain, clearly and early, what it will actually cost in design effort, material choices, and long-term monitoring commitment.
Verifying Compliance: Digital Tools Are Now Essential
The good news is that the industry has strong digital tools to verify standards compliance throughout the design process — and using them early prevents the painful scramble at planning or handover.
Key tools used in sustainability compliance work include Autodesk Insight, IES VE, One Click LCA, Sefaira, and Tally for performance analysis, energy simulation, and carbon tracking. Cove.tool now includes an AI-assistant tool called Vitras.AI, designed to automate reporting tasks with respect to the most recent zoning regulations, generating location-specific compliance reports automatically. Autodesk Forma provides real-time embodied carbon data in context at the planning stages, giving directional views on embodied carbon choices for major building systems such as construction type or facade system — while Autodesk Insight supports more detailed and rigorous evaluation through connection to the Revit Energy Analytical Model.
One Click LCA integrates with over 20 BIM platforms and is increasingly used to verify embodied carbon against LETI, RIBA, and UK NZCBS targets during design development. IES VE remains the industry standard for detailed dynamic thermal modelling — particularly important for projects targeting actual in-use performance data rather than design-stage estimates. The shift is away from a single compliance check at planning, toward continuous performance verification baked into the BIM workflow from concept onwards.
The most important shift in mindset: these tools shouldn’t be used to prove compliance after the design is done. They should be used to shape the design from the start.
The Bigger Picture — And Why It Actually Matters
I want to end with something that sometimes gets lost in the technical detail.
Every framework comparison, every framework table, every standards discussion exists for one reason: to slow and ultimately stop global warming. The built environment accounts for roughly 40% of global carbon emissions. Every project our industry delivers — every residential block, every hospital, every office campus, every data center — either contributes to that number or helps reduce it. There is no neutral position.
“Net zero” done properly isn’t a certificate on a wall or a line in a planning statement. It’s a building that consumes less energy than a conventional equivalent, built with materials that carry less embedded carbon, monitored through its operational life to confirm it’s actually performing as designed. That’s a meaningful contribution. “Net zero” done poorly is an offset purchase that lets a high-carbon building call itself sustainable — and that, frankly, is the kind of thing that erodes public trust in the entire industry.
The only way to give clients an honest answer is to specify which framework governs the project at appointment, document it, and hold the line throughout design and construction. Retrofitting a framework after design completion is expensive, demoralizing, and usually results in offsetting rather than genuine performance.
We owe our clients honesty. We owe the planet something more than a label.
