Performance-Based Fire Design Moving Beyond Prescriptive Rules
By Duncan Winsbury
Author of Performance-Based Building Design – From Regulation to Real-World Performance
Introduction
The evolution of fire safety engineering has been marked by one defining transition — the move from prescriptive codes to performance-based design.
Where prescriptive standards once dictated fixed dimensions, material ratings, and escape distances, performance-based approaches allow engineers to prove compliance through science rather than prescription.
This shift has transformed how modern buildings are conceived, tested, and justified — enabling safer, more sustainable, and more innovative architecture.
1. What Performance-Based Design Really Means
Performance-based fire design (PBFD) is founded on a simple principle:
A building’s fire safety should be demonstrated to meet defined performance objectives — not merely follow fixed rules.
Instead of “tick-box” compliance, PBFD uses engineering evidence to show that occupants can evacuate safely, structures will remain stable, and fire spread will be controlled under credible scenarios.
The approach is codified in BS 7974, which provides the overarching framework for fire safety engineering, supported by application guides PD 7974-1 to PD 7974-8.
2. Why Prescriptive Codes Have Limits
Prescriptive rules — such as those in Approved Document B or NFPA 101 — are invaluable for typical, low-complexity buildings.
However, as designs become taller, deeper, or more unconventional, these codes can constrain innovation or produce impractical outcomes.
Common limitations include:
- Arbitrary compartment sizes and travel distances that don’t reflect modern layouts.
- Inflexibility for mixed-use, open-plan, or heritage conversions.
- Lack of guidance for emerging technologies (e.g. photovoltaic façades, battery storage).
Performance-based design bridges this gap by quantifying fire safety outcomes rather than prescribing inputs.
3. Core Elements of Performance-Based Fire Design
| Component | Purpose | Examples |
| Fire Scenarios | Define credible ignition and growth events | Compartment fires, façade ignition, car park fire |
| Objectives & Criteria | Establish performance goals | Tenability (smoke/temp), structural stability, firefighter access |
| Analysis Methods | Quantify performance | CFD modelling (e.g. FDS, SmartFire), evacuation modelling (BuildingEXODUS, Pathfinder) |
| Verification & Sensitivity | Validate models and assumptions | Uncertainty analysis, calibration against benchmarks |
| Reporting & Documentation | Provide traceable evidence | Fire engineering report (FER) and fire strategy narrative |
These elements form a structured design pathway — ensuring transparency, reproducibility, and confidence in the final safety case.
4. The Role of the Fire Engineer
The fire engineer becomes the bridge between science and safety regulation, translating design intent into measurable performance outcomes.
Typical responsibilities include:
- Developing fire and evacuation models.
- Assessing structural fire resistance and compartment behaviour.
- Coordinating with architects, structural and M&E engineers.
- Presenting findings to Building Control, Fire Authorities, and other stakeholders.
As the Building Safety Act 2022 takes full effect, the fire engineer’s competence and accountability are central to maintaining the “Golden Thread” of safety information across the building lifecycle.
5. Tools and Techniques
Modern PBFD draws heavily on advanced computational methods:
- CFD Modelling (Computational Fluid Dynamics)
Simulates fire growth, smoke movement, and heat transfer.
Common tools: FDS, SMARTFIRE, PyroSim. - Evacuation Modelling
Quantifies RSET (Required Safe Egress Time) versus ASET (Available Safe Egress Time).
Tools include Pathfinder, BuildingEXODUS, Simulex. - Structural Fire Engineering
Uses temperature–time curves and finite element analysis to predict deformation and load-bearing capacity under fire conditions.
Together, these techniques allow multi-disciplinary teams to test hypotheses virtually before they’re built physically.
6. Benefits of Performance-Based Design
| Benefit | Description |
| Flexibility | Enables architectural innovation without compromising safety. |
| Optimisation | Reduces over-design and unnecessary cost by matching protection to risk. |
| Evidence-Based | Demonstrates compliance with quantitative data rather than interpretation. |
| Transparency | Provides a clear audit trail for regulators and stakeholders. |
| Sustainability | Supports adaptive reuse and refurbishment by tailoring solutions to existing constraints. |
PBFD allows safety to evolve alongside architecture — not lag behind it.
7. Challenges and Responsibilities
While the advantages are significant, performance-based methods demand a high standard of rigour and competence:
- Modelling uncertainty must be managed through conservative assumptions and sensitivity checks.
- Interdisciplinary communication is essential — results must be understood by non-engineers.
- Approval processes can vary, with some regulators still preferring prescriptive comfort zones.
- Documentation and traceability are vital — especially under the Building Safety Act’s new regime.
Ultimately, PBFD requires not only technical skill but professional integrity.
8. The Future — Towards Digital and Integrated Design
The next frontier is digital integration:
- BIM-linked fire models, allowing instant updates between geometry and safety data.
- Digital twins, enabling real-time monitoring and post-occupancy validation.
- AI-driven optimisation, helping engineers explore thousands of design permutations in seconds.
These tools will make fire safety predictive, adaptive, and continuously verifiable, closing the loop between design and operation.
Conclusion
Performance-based fire design represents a fundamental shift in how we define safety — from compliance by prescription to safety by proof.
It empowers engineers to tailor solutions precisely to the building, its use, and its occupants, ensuring resilience without restricting creativity.
As regulatory frameworks evolve, PBFD stands as the bridge between engineering innovation and legal accountability — a cornerstone of the safer, smarter, and more transparent built environment envisioned by modern fire safety legislation.
Further Reading
- BS 7974:2019 — Application of Fire Safety Engineering Principles to the Design of Buildings.
- PD 7974 Series — Application guides (1–8).
- Building Safety Act 2022 and Fire Safety (England) Regulations 2022.
- Winsbury, D. (2025). Performance-Based Building Design – From Regulation to Real-World Performance.
About the Author
Duncan Winsbury is a UK-based Fire Engineer specialising in performance-based design, risk-informed decision-making, and fire strategy development.
He is the author of Performance-Based Building Design and several companion volumes in the Fire Engineering Series, including Fire Protection Systems and Principles of Fire Engineering – Science, Safety and Solutions.
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