Draft. These pages were imported from the ARC Technical Criteria document (16 April 2026) and have not yet been reviewed in this format. Several thresholds are still being settled and are flagged on the pages concerned.

ARC Cool Buildings Standard

Thermal comfort and building performance in hot, and hot and humid, climates.

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ARC Technical Criteria

Overview

• Climate and weather - Why performance is assessed against the current climate rather than a fixed benchmark, and why benchmarks themselves keep moving.
• How ARC assesses building performance - How ARC judges a building: monitored environmental data against a humidity-modified adaptive comfort model, by climate category.
• Introduction - What this document is, who it is for, and ARC's aim of a building standard for hot and hot-humid climates where Passivhaus in one step is not realistic.
• Success criteria for building modelling and performance - What the ARC Cool Buildings Standard sets out to achieve: year-round thermal comfort through passive design, while mitigating danger during heatwaves.
• The ARC framework - two Steps and three Zones - The shape of the framework - two strategic Steps, then three Zones - and what it is designed to support.
• What influences thermal comfort - The personal and environmental factors comfort depends on, and why a single universal building standard across climates and cultures is so hard.
• What the Cool Buildings Programme provides - The five parts of the programme: design strategies, the comfort model, building science resources, prescriptive measures and exemplar buildings.

Patterns

• Designing a heat refuge - The passive measures that keep a heat refuge below its limit when the power is off: orientation, shading, reflective surfaces, heat-shedding roofs and window openings.
• Leveraging adaptive comfort - the three-zone strategy - Using the three-zone approach to arrange a building's form and layout, so it can still operate when the electricity supply is interrupted.
• Step 1 and Step 2 - Step 1 is a naturally ventilated building that can be retrofitted over time; Step 2 is fully mechanically conditioned but still able to run on natural ventilation.
• Zone 1 - mechanically cooled and ventilated - What a mechanically cooled and ventilated space must do, including ventilation when air conditioning is running.
• Zone 2 - the communal heat refuge - The communal heat refuge: a space large enough for all occupants, usable during extreme heatwaves.
• Zone 3 - transient and buffer spaces - Corridors, washrooms and other spaces people pass through, which may run hotter than zones 1 and 2 and can shade them.

Reference

• Defining and monitoring heatwaves - How heatwaves are defined and monitored internationally, and why the global south is poorly served by the existing arrangements.
• Defining heatwaves and the heat index - How heatwaves are defined, and why organisations increasingly express hot weather as a feels-like value or heat index.
• Heatwaves, power cuts and operational resilience - Why heatwaves and power cuts arrive together, and what designing for operational resilience means in practice.
• Measuring thermal comfort - the temperatures - Dry bulb, wet bulb and dew point temperature, and the heat index - what each measures and when it matters.
• Meeting everyday comfort needs - What claiming performance to the ARC standard requires: at least twelve months of measured data, and which comfort model applies where.
• Physiological adaptation to heat - How quickly people adapt to outdoor conditions, why a running mean beats a monthly average, and what has to be measured.
• R&D brief - air conditioning and ventilation for hot humid climates - The brief for research into air conditioning and ventilation suited to hot humid climates, and the constraints it has to work within.
• Resources - Where ARC's supporting material and tools can be found.
• Success criteria - the temperature thresholds - The temperature thresholds a monitored zone 1 or 2 space must meet, and the separate limits that apply during a heatwave.
• Temperatures of transient spaces during heatwaves - The limits for spaces people use for more than an hour a day, in hot dry and hot humid climates.
• The humidity-inclusive comfort model - The model behind the thresholds, why more humid climates need more stringent standards, and why operative temperature is the correct metric.
• Thermal comfort models - The models used to judge comfort, and the factors they take account of: clothing, activity, humidity and air speed.