The ARC comfort model¶
ARC uses a humidity-inclusive adaptive comfort model. More humid climates require more stringent comfort standards, because the body's ability to sweat is diminished in humid air.
Claiming that buildings are performing to the ARC standard requires using at least 12 months of measured data for interior and exterior temperature and humidity, and entering this data into the ARC comfort model to gauge compliance with the criteria.
This exercise can be carried out for any space in the building that is being monitored. The performance of the building as a whole can be inferred from these results, but ARC encourages further monitoring and investigation of any areas where occupants report thermal discomfort - in order to help design and building teams, and the cool buildings community, learn and improve their practices.
Use a local model where one exists¶
The comfort model used will depend on the location. With hundreds of local surveys conducted worldwide based on the adaptive comfort method, many countries have identified what is found to be comfortable for their local populations - some, such as India, incorporating it into an official standard.
Where these local survey results are available, project owners can show that their building meets localised comfort expectations.
Match the study to the context
It is important that the local study used matches the project's specific context as much as possible.
A comfort study of residents in naturally ventilated houses would not be appropriate for assessing the performance of a centrally air-conditioned office tower in a city centre. This is due to differing expectations, acclimatisation - to unconditioned versus conditioned spaces - and occupants' differing levels of control and opportunities to adapt their environment.
That same study might, however, be used to assess designs for naturally ventilated office space where occupants have desk fans and relaxed dress codes.
The ARC website provides a database of these studies.
Where no local model exists¶
For countries where a local model is not available, ARC has developed simple success criteria to guide designers and builders.
These are based on standard comfort models, but informed by a 'designer-friendly relative-humidity-inclusive' adaptive comfort model that "significantly extends the range of acceptable indoor conditions for designing low-energy naturally conditioned buildings all over the world".
This is the approach ARC applies when assessing the performance of buildings, the aim being to present building performance consistently across ARC's Cool Buildings programme.
The humidity-inclusive model¶
The humidity-inclusive comfort model 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. See what influences thermal comfort.
The acceptable range for comfort in the model allows 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%.
Air temperature or operative temperature?¶
Operative temperature - a weighted average of dry bulb air temperature and mean radiant temperature - is technically the 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, the assessment can be improved for accuracy by using it.
A further complication arises where radiant temperatures are extremely asymmetrical - for example where certain parts of a room, such as windows or areas of ceiling, are especially hot. Theoretically more sensors would be required to pick up this thermal asymmetry, and more analysis to understand the impact on occupants.
Avoiding analysis paralysis
Where sufficient data is not yet available, 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.
Worked example¶
The source document illustrates performance against ARC's success criteria using measured data from a 10-person communal domestic accommodation building built in Tanzania in 2023, with data from 2024–2025, courtesy of Simmonds.Mills LLP, Huda Elsherif and Archie Worthington.
Figures not yet included
The source refers to two figures at this point - the influence of relative humidity on adaptive thermal comfort, and the measured Tanzanian building data. These charts have not yet been prepared for the wiki, and the underlying research citation is recorded in the source only as "Marika et al" without a full reference.
Source: ARC Technical Criteria - Comfort model - Meeting everyday comfort needs
Reference · confidence high · Imported 2026-08-29, not yet reviewed · next review 2026-11-29
Tags: comfort, model, humidity, monitoring, adaptive-comfort
Citation key: comfort-model