7.1 Thermal Performance (T01) & Verified Thermal Comfort (T02)

7.1 Thermal Performance (T01) & Verified Thermal Comfort (T02)

Core Exam Takeaway: Thermal Comfort has exactly one precondition (T01) and six optimizations (T02–T07), and carries 7 scored exam questions. T01 is unusual in that all three of its Part 1 options can be satisfied by deferring to another feature: Option 2 requires T06, Option 3 requires two points in T02, and the looser PMV band requires two points from T03 or T04. Memorize PMV ±0.5 / 90% / 90% and the 80% and 90% satisfaction thresholds in T02.

The six variables of thermal comfort

Thermal sensation is not temperature. ASHRAE Standard 55 models it from six variables — four environmental and two personal:

Those six feed the Predicted Mean Vote (PMV) — a −3 (cold) to +3 (hot) scale where 0 is neutral — and its companion Predicted Percentage Dissatisfied (PPD). Because thermal preference varies between individuals, PPD can never reach zero: at PMV = 0, PPD is still about 5%. This is precisely why WELL pays separately for zoning (T03) and individual control (T04) rather than chasing a single perfect setpoint.

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Feature T01: Thermal Performance — Precondition

Intent: provide a thermal environment that the majority of building users find acceptable.

T01 Part 1 — Provide Acceptable Thermal Environment

Option 1: Performance verified environmental conditions

(a) Mechanically conditioned regularly occupied spaces meet one of:

(b) Naturally conditioned regularly occupied spaces meet the adaptive comfort model:

(c) Mixed-mode-conditioned spaces meet the requirements for both mechanically and naturally conditioned spaces, when each is in operation.

Option 2: Long-term thermal data — both:

• (a) The project meets Feature T06: Thermal Comfort Monitoring.
• (b) Temperature and humidity data covering at minimum the previous six months satisfy one of:
  1. One of the PMV or temperature ranges in Option 1. Dry-bulb temperature may be used in place of operative temperature, and naturally conditioned projects must also measure outdoor air temperature; or
  2. Dry-bulb temperature between 70–77 °F (21–25 °C) for at least 90% of standard occupied hours, with designed air velocity not more than 40 fpm (0.2 m/s) at 5.6 ft (1.7 m) above the floor.

Option 3: Thermal comfort surveys — the project achieves at least two points in Feature T02: Verified Thermal Comfort.

For commercial kitchen spaces: the operative temperature in the kitchen does not exceed 80 °F (27 °C).

Multifamily note: Bronze or Silver achievable without dwelling-unit testing; Gold and Platinum not. WELL Core guidance: whole building; mechanically conditioned or mixed-mode spaces must provide heating and cooling capacity in leased spaces but are not required to install ducts there; performance testing is conducted in regularly occupied non-leased spaces if present.

T01 Part 2 — Monitor Thermal Parameters

For all spaces except dwelling units.

Option 1: Annual testing. Dry-bulb temperature, relative humidity, air speed (only for projects using the elevated air speed method) and mean radiant temperature are monitored in regularly occupied spaces at intervals no less than twice a year — including once in June, July or August and once in December, January or February — with results submitted annually. Sampling points comply with the Performance Verification Guidebook. If a WELL Performance Testing Agent takes the measurements per the guidebook, results may be averaged and used for recertification.

Option 2: Continuous monitoring. The project meets Feature T06.

WELL Core guidance: non-leased spaces.

+-----------------------------------------------------------------------------+
|            T01: THREE ROUTES, TWO OF WHICH DELEGATE ELSEWHERE               |
|                                                                             |
|   OPTION 1  MEASURE NOW      PMV +/-0.5 : 90% of hours : 90% of spaces       |
|                              OR PMV +/-1.0 : 98% : 95% PLUS >=2 pts from      |
|                                 T03 and/or T04                               |
|                              Naturally conditioned -> ADAPTIVE MODEL          |
|                                                                             |
|   OPTION 2  MEASURE OVER     T06 achieved + >=6 months of data in an          |
|             TIME             Option 1 range, OR 70-77 F (21-25 C) for >=90%   |
|                              of standard occupied hours with designed air     |
|                              velocity <= 40 fpm (0.2 m/s) at 5.6 ft (1.7 m)   |
|                                                                             |
|   OPTION 3  ASK PEOPLE       >= 2 points in T02 (i.e. >= 80% satisfaction)     |
|                                                                             |
|   Commercial kitchens: operative temperature must not exceed 80 F (27 C).     |
+-----------------------------------------------------------------------------+

[!IMPORTANT] The ±1.0 PMV band is not free. Widening the band from ±0.5 to ±1.0 requires the project to earn at least two points in T03 Thermal Zoning, T04 Individual Thermal Control, or a combination — WELL trades a looser central setpoint for genuine occupant control. This conditional structure is one of the most reliably examined details in the concept.

[!TIP] The adaptive model is not a loophole; it is different physics. People in naturally ventilated buildings acclimatize to and expect seasonal drift, so their comfort band tracks recent outdoor conditions. The 0.31 slope and the valid range of 50–92 °F (10–33.5 °C) prevailing mean outdoor temperature both come from ASHRAE 55, and elevated air speed under occupant control can extend the upper bound.

[!WARNING] Note what T01 does not contain: a fixed heating and cooling setpoint, a required relative humidity range, or a general air-speed limit. Humidity is T07 (30–60%), and the only air-speed number in T01 is the 40 fpm (0.2 m/s) designed velocity at 5.6 ft (1.7 m) that accompanies Option 2's simplified dry-bulb range.

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Feature T02: Verified Thermal Comfort — Optimization (3 pt / WELL Core 3 pt)

Intent: enhance thermal comfort and productivity by ensuring that a substantial majority of building users (above 80%) perceive their environment as thermally acceptable.

T02 Part 1 — Survey for Thermal Comfort

A post-occupancy survey is administered at least twice a year — including once in June, July or August and once in December, January or February — at least six months after occupancy, satisfying:

(a) All regular occupants are invited to participate in an anonymous survey, with responses collected from:

(b) The survey assesses overall satisfaction with thermal performance and identifies thermal comfort-related issues, using either the sample survey in Appendix T1 or any pre-approved survey listed in the Occupant Survey feature.

(c) Results comply with one of these satisfaction thresholds:

WELL Core guidance: whole building; all regular occupants must be invited; the survey scope may be limited to thermal conditions in non-leased spaces.

[!IMPORTANT] T02 has no 1-point tier — it awards 2 points at 80% satisfaction and 3 points at 90%. That matters structurally, because T01 Option 3 requires "at least two points in T02," which means 80% satisfaction is the minimum that satisfies the precondition by survey.

[!TIP] The seasonal bracketing is deliberate and testable. Both T01 Part 2 Option 1 and T02 Part 1 require measurement or survey once in June–August and once in December–February, because a building that is comfortable in the shoulder seasons may fail badly at design conditions. Note also the inverted response-rate ladder: small populations must supply a higher percentage (80% below 20 occupants) than large ones (35% above 45), because small samples are statistically fragile.