WELL v2 Thermal Comfort: Temperature, PMV, and Humidity Requirements (2024)

A 2% drop in work performance per 1°C temperature rise above 25°C (77°F). That is the figure WELL v2 cites in feature T03. Miss T01, the Thermal Comfort precondition, and certification stops. Optimization points cannot replace T01, although T01 Option 3 can be met with at least 2 points from the T02 occupant survey. WELL v2’s Thermal Comfort features T01 through T07 set PMV targets, temperature bands, humidity limits, zoning rules, and occupant survey thresholds for every regularly occupied space.

What are the WELL v2 thermal comfort numbers at a glance?

WELL Thermal Comfort is the certification concept, governed by precondition T01 and optimizations T02 through T07, that defines acceptable indoor temperature, humidity, and air movement in every regularly occupied space. One failed precondition blocks WELL v2 certification entirely.

All WELL v2 project types must pass T01. Multifamily residential projects may achieve Bronze or Silver without dwelling-unit testing of preconditions; Gold and Platinum require it. Under T01 Part 2 Option 1, dry-bulb temperature, relative humidity, mean radiant temperature and (only where elevated air speed is used) air speed are monitored at least twice a year, once in June–August and once in December–February, with results submitted annually; Option 2 is met by T06 continuous monitoring. Part 2 does not apply to dwelling units.

Why does WELL set specific temperature thresholds?

PMV, or Predicted Mean Vote, is the 7-point thermal sensation scale, from -3 (cold) to +3 (hot), of Fanger’s thermal comfort model (standardized in ISO 7730). WELL v2 cites ASHRAE 55-2013, which contains the PMV method for mechanically conditioned spaces and the adaptive comfort model for naturally conditioned spaces. PMV is calculated from six parameters: air temperature, mean radiant temperature, humidity, air speed, metabolic rate, and clothing insulation. The adaptive model links acceptable indoor operative temperature to the outdoor prevailing mean temperature. T01 accepts both pathways, and both apply to regularly occupied spaces. For context, WELL’s T03 cites an average 2% decrease in work performance per 1°C (1.8°F) of air temperature rise when air temperature is above 25°C (77°F).

What does T01 require for mechanically conditioned spaces?

T01 Thermal Performance is the precondition requiring regularly occupied spaces to meet one of three compliance options, per WELL v2. Option 1 (performance-verified conditions) sets, for mechanically conditioned spaces, PMV within ±0.5 for at least 90% of occupied hours in at least 90% of regularly occupied spaces, per ASHRAE 55. A looser band is also available: PMV ±1.0 for 98% of hours in 95% of spaces, but only if the project earns at least 2 combined points from T03 and T04.

Option 2 replaces modeling with long-term data from T06 covering at least the previous six months: either the Option 1 ranges (dry-bulb temperature may stand in for operative temperature) or dry-bulb temperature between 21°C and 25°C (70–77°F) for at least 90% of standard occupied hours, with designed air velocity of no more than 0.2 m/s (40 fpm) at 1.7 m (5.6 ft) above the floor.

Option 3 requires at least 2 points from the T02 occupant survey instead of environmental data. Commercial kitchen spaces have their own single requirement: operative temperature must not exceed 27°C (80°F).

How does T01 apply to naturally ventilated buildings?

The adaptive comfort model is the WELL v2 T01 compliance pathway for naturally conditioned buildings, linking acceptable indoor operative temperature to the outdoor prevailing mean temperature (tpma), per ASHRAE 55-2013. WELL’s table lists a prevailing mean outdoor temperature from 10°C (50°F) to 33.5°C (92°F).

Within the valid tpma range, the minimum acceptable indoor operative temperature is tpma × 0.31 + 14.3°C. The maximum is tpma × 0.31 + 16°C. Occupant-controlled elevated air speed, per ASHRAE 55-2013, may increase the maximum.

Mixed-mode buildings, which use both mechanical and natural conditioning at different times, must meet the requirements for naturally conditioned spaces when natural conditioning is in operation and the requirements for mechanically conditioned spaces when the mechanical system is in operation (T01 Part 1, Option 1c).

How do thermal zoning points work under T03?

T03 Thermal Zoning is the 2-point optimization that grants granular temperature control by limiting zone sizes and requiring thermostat access in every regularly occupied space, per WELL v2.

At least 90% of regularly occupied spaces must have thermostat control: either an in-zone thermostat or a digital interface on a computer or phone. Maximum zone size is 60 m² (650 ft²) or 10 occupants, whichever is larger. Temperature sensors must be positioned at least 1 m (3.3 ft) from exterior walls, windows, diffusers, and heaters per WELL v2 T03. WELL Core projects earn 3 points from T03; standard WELL v2 projects earn 2. T04 Individual Thermal Control adds up to 3 more points for 1 point for personal cooling options (for example a user-adjustable thermostat, desk or ceiling fan, or a cooled chair), 1 point for personal heating options (for example a user-adjustable thermostat, a parabolic heater, a heated chair or footwarmers, or blankets) and 1 point for a flexible dress code. T03 and T04 points combine to unlock the PMV ±1.0 band under T01.

What do occupant surveys require under T02?

T02 Verified Thermal Comfort is the 3-point optimization that replaces or supplements environmental data with post-occupancy surveys, administered at least twice per year, per WELL v2. Survey rounds must occur once in summer (June, July, or August) and once in winter (December, January, or February), starting at least 6 months after occupancy.

Minimum response requirements vary by project size:

Points scale with satisfaction rate: 80% of respondents satisfied earns 2 points; 90% satisfied earns 3 points. T02 also functions as the compliance pathway for T01 Option 3, making T02 both an optimization and a precondition alternative for thermally challenging buildings. Projects pursuing T01 via Option 3 must achieve at least 2 T02 points before T01 passes.

What are the T07 humidity requirements?

T07 Humidity Control is the 1-point optimization (2 points for WELL Core projects) that requires regularly occupied spaces to maintain relative humidity between 30% and 60%, per WELL v2. The T07 rationale links high humidity to mold and fungal growth and to bacteria and dust mites, and cold, dry air to airway, skin and eye irritation. Three compliance options are available.

Option 1 (mechanical capability): The HVAC system must be capable of adding or removing moisture to maintain 30%–60% relative humidity at all times. Option 2 (energy modeling): Annual energy models must show 30%–60% relative humidity for at least 98% of all business hours. Option 3 (monitoring data): At least 6 months of humidity monitoring data must show 30%–60% for 98% of business hours. Option 3 requires T06 Thermal Comfort Monitoring as a prerequisite.

High-humidity areas, including wet zones such as pool decks and commercial kitchens, are excluded from T07. Projects undergoing recertification must use all humidity data collected since prior certification when applying Option 3.

What do teams most often get wrong about WELL v2 Thermal Comfort?

Five points deserve attention before submission.

1. Monitoring timing missed. T01 Part 2 Option 1 requires monitoring at least twice a year, including once in June, July or August and once in December, January or February, with results submitted annually. Option 2 (continuous monitoring through T06) is the alternative.

2. Option 2 attempted without T06. T01 Option 2 requires T06 Thermal Comfort Monitoring as a prerequisite. The long-term data pathway needs T06 in place and at least six months of data.

3. Zone size calculated on area only. T03 determines zone size as 60 m² (650 ft²) or 10 occupants, whichever is larger. Check both the area and the occupant count against the standard’s text.

4. Dwelling units skipped on Gold/Platinum multifamily. Bronze and Silver do not require dwelling-unit testing of preconditions. Gold and Platinum do, per WELL v2 T01.

5. Sensors placed near glazing. T03 requires sensors at least 1 m (3.3 ft) from exterior walls, windows and doors, direct sunlight, air supply diffusers, fans and heaters, so readings represent the occupied zone.

What to verify before submitting for WELL thermal comfort?

• T01 compliance option selected (Option 1, 2, or 3) and documented per WELL v2 T01
• PMV calculations confirm ±0.5 for 90% of occupied hours in 90% of spaces (Option 1), per ASHRAE 55
• If using PMV ±1.0 band: at least 2 combined points from T03 and T04 confirmed per WELL v2 T01
• If using Option 2: T06 monitoring activated; dry-bulb 21–25°C (70–77°F) for 90% of occupied hours verified
• If using Option 2: air velocity confirmed ≤ 0.2 m/s (40 fpm) at 1.7 m (5.6 ft) above floor
• If using Option 3: at least 2 T02 points achieved before T01 submission
• Natural ventilation: outdoor tpma confirmed between 10°C (50°F) and 33.5°C for adaptive model use
• Commercial kitchen operative temperature confirmed ≤ 27°C (80°F) per WELL v2 T01
• T01 Part 2 route chosen: monitoring at least twice a year (one round in June/July/August, one in December/January/February), or continuous monitoring through T06 (Option 2)
• T02 survey response thresholds met per project size: 35% of occupants if more than 45 regular occupants, per WELL v2 T02
• T03 zone sizes verified: 60 m² (650 ft²) or 10 occupants maximum per zone, per WELL v2 T03
• Temperature sensors positioned at least 1 m (3.3 ft) from exterior walls, windows, direct sunlight, and diffusers per T03
• T07 humidity system confirmed capable of maintaining 30%–60% RH per WELL v2 T07
• Multifamily Gold/Platinum projects: dwelling-unit T01 testing scheduled
• Data submission pathway to WELL digital platform confirmed for annual reporting