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.
The humidity-inclusive comfort model, researched by Marika et al, is based on 63 studies in 13 countries with hot climate regions. The principal benefit of the model is that it acknowledges that more humid climates require more stringent comfort standards, because the human body's ability to sweat is diminished in more humid climates. The acceptable range for comfort in the comfort model allows for projects in different locations to adopt a bespoke target based on local humidity levels. This safely widens the applicability, range and accuracy of the ARC Cool Buildings approach: in their published research, the researchers show that the widely adopted ASHRAE method overestimates overheating by 30%.
Figure ##: Marika et al: The influence of relative humidity on adaptive thermal comfort.
Using the measured performance for a 10-person communal domestic accommodation building, built in Tanzania in 2023 we can illustrate how the building performs against ARC’s success criteria, see Fig## below.
Figure ##: measured data from 2024 – 2025, courtesy of Simmonds.Mills LLP, Huda Elsherif, Archie Worthington
In the above illustration the graph’s vertical axis shows dry bulb air temperature only - not the combined effects of radiant and air temperature (operative temperature). Operative temperature (weighted average of dry bulb air temperature and mean radiant temperature) is technically he correct metric for demonstrating building performance using this model. Where operative temperature can be calculated (from monitoring of room radiant temperatures using black bulb thermometers) then the graph can be improved for accuracy by using operative temperature. A further complication may arise where radiant temperatures are extremely asymmetrical – for example certain parts of a room, such as windows or some areas of ceiling are especially hot. Theoretically more sensors would be required to pick up this thermal asymmetry and more analysis associated with understanding the impact on occupants. However, where sufficient data is not yet available, and to avoid ‘analysis paralysis’, use air temperature as a proxy for operative temperature, if necessary; use operative temperature in preference if suitable monitoring data is available, and where possible factor in radiant asymmetry where detailed monitoring and analysis is being carried out.
Open questions on this page
These are unresolved in the source document - the author's own queries, and the figures and citations still to be filled in. They are repeated here rather than resolved, because a threshold shown as settled when it is still under discussion would be misleading.
- Figure ##: Marika et al: The influence of relative humidity on adaptive thermal comfort
- Figure ##*: measured data from 2024 – 2025, courtesy of Simmonds
Confirm any of these with ARC before relying on them for a project.
Source: ARC Technical Criteria - 195
Reference · confidence medium · Imported 2026-09-12, not yet reviewed · next review 2026-12-12
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Citation key: humidity-inclusive-comfort-model