T02: Enhanced Thermal Performance

(3 points)

INTENT

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

SUMMARY

This WELL feature requires projects to provide high levels of thermal comfort through compliance with design requirements or by determining occupant satisfaction through a survey.

ISSUE

Building users who are satisfied with their thermal environment have been shown to be more productive in the workplace, while thermal discomfort is associated with sick building syndrome symptoms and other conditions that lead to a decrease in productivity. Unfavorable levels of heat, humidity and ventilation are associated with symptoms of itchy eyes, headache and throat irritation in building users. Studies have also shown that only 11% of office buildings surveyed in the U.S. provide thermal environments that meet generally accepted goals of human satisfaction. Similarly, as many as 41% of office workers have expressed dissatisfaction with the thermal environment.

SOLUTIONS

Achieving optimal thermal comfort requires some level of control over the six core thermal comfort parameters in any given environment (air temperature, humidity, air movement, mean radiant temperature of surrounding surfaces, metabolic rate, clothing insulation). This can practically be achieved through correct sizing of HVAC equipment, optimal system control, passive building design strategies, and/or through optimizing personal factors. Furthermore, building occupants are an invaluable source of information that can be used for improving the performance of buildings. Thermal comfort surveys allow projects to objectively gauge which building services and design features are or are not performing well, and help to prioritize the steps needed to improve occupant thermal comfort satisfaction and workplace productivity. If survey results indicate that percentage of occupants dissatisfied with thermal conditions in the building exceeds the targeted thresholds, it is necessary to develop a detailed plan for action and commitment to address occupant dissatisfaction with thermal conditions.

IMPACT

The impact of increasing the number of people satisfied with their thermal environment is substantial, as it extends beyond comfort and is linked to improved health, well-being and productivity. WELL encourages projects to go beyond the minimum requirements of the standards for thermal comfort listed in Feature T01: Thermal Performance.

REQUIREMENTS

Part 1

Enhance Thermal Environment (1 point)

Verified by MEP, Performance Test, Professional Narrative

For All Spaces except Commercial Kitchen Spaces

Choose between the following:

Option 1. Mechanically ventilated spaces:

The following requirement is met: 

1. During all standard occupied hours of the year, all regularly occupied spaces achieve thermal conditions representing Predicted Mean Vote (PMV) levels within +/- 0.5; PPD ≤ 10% (as per ASHRAE 55-2013, ISO 7730:2005 or EN 15251:2007).

    

Option 2. Naturally ventilated spaces:

During all standard occupied hours of the year, all regularly occupied spaces achieve one of the following thermal conditions:

1. 90% acceptability limit (as per ASHRAE 55-2013).

2. Class I acceptability limit (as per EN 15251:2007).

Note: Mixed-mode-conditioned spaces are deemed compliant with the feature if requirements for both mechanically and naturally conditioned spaces are satisfied.

Part 2

Achieve Thermal Comfort (Max: 3 points)

Verified by Survey Materials, Professional Narrative

For All Spaces except Commercial Kitchen Spaces & Dwelling Units

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, which satisfies the following conditions:  

1. All regular building occupants are invited to participate in the anonymous survey.

2. Responses are collected from the following number of respondents:

   1. At least 35% the total occupants if more than 45 occupants are solicited.
   2. At least 15 occupants if solicited occupants number is between 20 and 45.
   3. At least 80% of the total occupants if fewer than 20 occupants are solicited.

3. The survey includes an assessment of overall satisfaction with thermal performance and identification of thermal comfort-related issues in accordance with either:

   1. The sample survey in Appendix T1.
   2. Any pre-approved survey listed in Part 1: Administer Project Survey in Feature C03: Occupant Survey.

4. The results of the survey responses comply with one of the target satisfaction thresholds as specified in the table below:

   Thermal Comfort Satisfaction Thresholds	Points
   80% of regular occupants	2
   90% of regular occupants	3

 

Note: Surveys may be given to occupants via a website, phone application or handed out as hard copies. The surveys should be distributed during mid-morning or mid-afternoon, at least 30 minutes after arrival or after a lunch break. The distribution of the results are submitted as part of documentation for this feature. See example in Appendix T1. For initial certification, only the results from the first survey are required. For recertification, the median value of occupant satisfaction from the previous six surveys is used.

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