Thermal comfort verification under the WELL Building Standard, a certification mark of the International WELL Building Institute, uses on-site measurement of dry-bulb air temperature and relative humidity to provide evidence of conditions in the completed project. This page explains the role of those two measured quantities, how they differ from design-stage comfort calculations and how operating conditions affect the evidential value of the result. It does not address humidity control, ventilation hygiene, duct cleaning or the health effects of indoor conditions.
Thermal Comfort is one of the five concepts included in on-site performance verification under the standard, together with Air, Water, Light and Sound. The field work is carried out by a WELL Performance Testing Agent working for an approved performance testing provider. The agent records the conditions found at the selected locations and prepares the resulting evidence.
A separate WELL Reviewer then assesses those results alongside the project documentation and decides whether the relevant feature has been achieved. The site measurement is therefore not itself a certification decision. It is one part of the evidence considered during review.
This distinction matters when programmes are being planned. The date on which measurements are completed is not necessarily the date on which the feature is determined. Records still need to be compiled, submitted and reviewed, and any questions about the relationship between field conditions and project documentation may need to be resolved.
The scheme verifies thermal conditions through measurement of dry-bulb air temperature and relative humidity. Dry-bulb air temperature records the air temperature at the test location without introducing a separate moisture-based temperature quantity. Relative humidity records the moisture condition of the air as a proportion relative to its capacity at that temperature.
For certification purposes, these are measured quantities rather than descriptive impressions. Statements that a room felt warm, cool, dry or humid do not replace the physical evidence. The result must be tied to a location, time and operating condition that can be understood during review.
The two quantities should also remain linked to the same test event. A temperature value from one period and a relative-humidity value from another may not describe a single operating condition unless the applicable procedure expressly allows that arrangement. Clear records help demonstrate what was present when the measurements were taken.
A design comfort calculation is based on assumptions about the proposed building, systems, occupancy, loads and operating parameters. It helps the design team evaluate whether the intended arrangement is expected to provide suitable conditions. The calculation is predictive and depends on the accuracy of those assumptions.
On-site measurement answers a different question. It records the dry-bulb air temperature and relative humidity present in the actual space during the verification event. The building may have been constructed, commissioned, fitted out and operated differently from the modelled assumptions, so measured performance cannot be inferred solely from the design report.
The scheme uses this distinction to examine the operating project rather than only its stated intent. A well-developed calculation may support the documentation, but the field evidence shows what was physically present at the selected location. Neither form of evidence should be misrepresented as the other.
Temperature and relative humidity can change with system operation, occupancy, internal loads, solar conditions, door use and other aspects of building activity. The test record therefore needs to describe the relevant operating state rather than presenting the readings as context-free numbers.
The performance-verification guidebook does not establish a universal rule that all testing must occur during normal occupied hours. Timing is determined by the relevant parameter and project type, with defined exceptions, including circumstances in which unoccupied-space measurement is permitted. The applicable instruction governs the condition that should be represented.
Facilities teams should avoid assuming that any convenient stable period is automatically suitable. A temporarily altered setpoint, incomplete commissioning state or exceptional shutdown may produce measurements that do not correspond to the operating condition required by the feature. The test should reflect the applicable scheme condition and be documented honestly.
Thermal comfort measurement should be scheduled when the relevant building systems and spaces are sufficiently complete to represent the intended operation. Temporary cooling, open construction zones, incomplete controls or unbalanced commissioning conditions can weaken the relationship between the result and the finished project.
The selected areas should also be in their intended use or in a state that can reasonably represent that use. A room filled with construction materials, isolated from its normal system or awaiting final fit-out may not provide meaningful evidence of the condition the project seeks to demonstrate.
Readiness is therefore more than physical access. It includes functioning systems, stable room identification and an operating state that corresponds to the applicable feature. Where the site is handed over in phases, the verification plan should align with the actual certification boundary and the areas that are ready.
A measured condition that differs from the design calculation does not by itself identify the reason. The cause may relate to system operation, controls, occupancy, fit-out, commissioning, loads or assumptions in the design information. Performance verification records the result; it is not automatically a complete investigation into the source of the difference.
Where the measured evidence does not support the pursued feature, the project team may need to examine whether the operating arrangement is complete, representative and consistent with the submitted documents. Any adjustment should reflect a sustainable operating condition rather than a temporary change introduced only for the test.
A favourable result should also be interpreted within its limits. It supports the applicable feature at the selected test locations and conditions. It does not establish that every part of the building will remain identical at every time or under every possible operating state.
Each result should be traceable to a clearly identified space, time and operating condition. The dry-bulb air temperature and relative humidity readings should be associated with the same location record, and the room naming should correspond with the plans and submission documents used by the reviewer.
The WELL Reviewer considers the field evidence together with the wider project material. Design calculations may explain the intended comfort strategy, while the measurements demonstrate the condition found during verification. The decision about feature achievement belongs to the reviewer, not to the testing agent, facilities team or design consultant.
Consistent documentation is especially important where spaces have changed use or names during delivery. A reading associated with an outdated room label may be difficult to reconcile with the final drawings. The evidence should describe the project as it exists at the time of testing.
This page addresses only dry-bulb air temperature and relative humidity as measured quantities under the scheme. It does not explain system design, occupant surveys, humidity-control strategies or the causes and consequences of thermal complaints.
Sampling quantity, floor-count logic, area bands and the rules for selecting test locations are addressed separately on the page titled "Sampling points and test locations". That neighbouring page governs how the wider verification plan distributes points across the project.
The separation is deliberate because a measurement method and a sampling plan answer different questions. This page explains what is measured and why operating evidence differs from prediction; the location page explains how the scheme structures the number and placement of test points.
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The physical quantities are dry-bulb air temperature and relative humidity. They are recorded at selected project locations under the operating condition required by the applicable feature.
No. A design calculation predicts performance from assumptions, while on-site measurement records conditions in the completed project. The reviewer may consider both, but they are different forms of evidence.
There is no universal rule requiring every parameter to be measured during normal occupied hours. Timing and occupancy conditions depend on the applicable parameter and project type, and the guidebook includes defined exceptions for unoccupied-space measurement in some circumstances.
No. The agent carries out and documents the on-site work for an approved performance testing provider. A separate WELL Reviewer assesses the results with the submitted documentation and decides whether the feature is achieved.
No. The result supports the applicable feature for the selected locations and test conditions. It should not be generalised to every area, season or operating state beyond the scope of the submitted evidence.
This site is an independent information resource. It is not affiliated with, endorsed by, accredited by or authorised by the International WELL Building Institute pbc, which owns the WELL certification mark, and it is not a certification body, an assessor, a performance testing provider or a scheme partner. Nothing on this page can certify, assess or award anything under the scheme, and nothing here is a substitute for the scheme's own published documentation. Requirements are summarised factually rather than reproduced; where a numeric threshold is stated it is drawn from documentation the scheme's owner publishes openly, and the specific figure is cited rather than the table it sits in. Certification under the scheme is voluntary and is not required by any authority in the United Arab Emirates.