Artificial intelligence (AI) policy: ASHRAE prohibits the entry of content from any ASHRAE publication or related ASHRAE intellectual property (IP) into any AI tool, including but not limited to ChatGPT. Additionally, creating derivative works of ASHRAE IP using AI is also prohibited without express written permission from ASHRAE. For the full AI policy, click here. 

Close
logoShaping Tomorrow’s Global Built Environment Today

Thermal Comfort

Mythbusters

Share This

Thermal Comfort

Common Myths

Thermal Comfort Mythologies:
The Realities of ASHRAE Standard 55 – the DO NOT, IS NOT, & CAN NOT

  • Indoor air quality IS NOT the same as thermal comfort; different physiological & neurological systems.
  • ASHRAE’s IAQ Standards 62.1 and 62.2 explicitly state they DO NOT address thermal comfort.
  • ASHRAE Standard 55 explicitly states it DOES NOT address indoor air quality.
  • Convection and air temperature (dry bulb) ARE NOT the primary factors in thermal comfort.
  • The numerical value on a thermostat DOES NOT represent thermal comfort.
  • People sense heat loss, retention and gain through their skin, NOT the heat loss and gain in the space.
  • Practitioners CAN NOT make a space or building thermally comfortable—thermal comfort is a state of mind.
  • Practitioners CAN NOT make a person feel thermally comfortable—perception is subjective.
  • HVAC equipment CAN NOT deliver thermal comfort—it can provide mass (water/air) and energy (heat/coolth), nothing more, nothing less.
  • Standard 55 applies to commercial AND residential spaces, and its principles can be applied to other occupied spaces not governed by different standards, such as healthcare.
  • For healthcare and medical procedure spaces, see ASHRAE Standard 170.
  • Standard 55 DOES NOT concern itself with the mechanics of heating, ventilation and air-conditioning (HVAC).
  • Even ADPI assessment is not a requirement of Standard 55, though it will influence the airflow in a space.
  • Standard 55 DOES NOT have strict requirements—it works within a combination of factors and ranges.
  • IMPORTANT: Load calculations and HVAC design ARE NOT in themselves thermal comfort design procedures, nor are they requirements of ASHRAE Standard 55.
  • IMPORTANT: The air temperature differential between the inside and outside and used in load calculations, is for sizing equipment, ducts, pipes, and heat terminal units. The exercise’s objective is to maintain the indoor air temperature as witnessed by the value on the thermostat, as required by codes, which is NOT a proxy for thermal comfort.
  • Analysis for design and compliance must start well before the design of the HVAC system.
  • The objective is to create environmental conditions for people to sense (physiological) and perceive (psychological) thermal comfort based on all the factors and ranges defined in Standard 55.

IMPORTANT

ASHRAE Standard 55 IS NOT biased in favour of male office workers, as has been reported in the press. The standard uses the PMV/PPD index which was based on the European ISO7730 Standard which used studies based on both genders of various ages. From an academic perspective, there are some variances in sensation and perception. However, these do not fully explain the magnitude of differences. The primary source of differences is choices or mandates in clothing policy. Relative to those wearing lighter clothing, those wearing heavier clothing will want cooler spaces. Making thermal discomfort a gender issue distracts from the prime problems: flaws in architecture, enclosures, interior and mechanical systems. Inflexible adaption (e.g., clothing) policies is also part of the problem. Perpetuating the gender thermostat war only exacerbates the illiteracy in thermal comfort knowledge.

See ASHRAE media rebuttal August 3rd, 2015, “ASHRAE Statement in Response to Nature Climate Change Article on Thermal Comfort.”


Thermal Comfort Mythologies: The Realities of ASHRAE Standard 55 – The CAN DO’s

All design practitioners CAN:

  • accept thermal comfort (a condition of mind) requires an integrated design process; when done correctly and in the correct order, most people will not experience discomfort.
  • use four-pillar collaboration to create conditions (combination of factors) for the representative occupant to sense and perceive comfort.

Mechanical practitioners CAN:

  • provide warmth and coolth and control moisture and airspeed in a space/building—nothing more, nothing less.

Architectural, enclosure and interior systems practitioners CAN:

  • accept that the integrated design process removes sole responsibility for thermal perceptions in the exclusive hands of the mechanical team; thermal comfort always starts with the architecture, enclosure, and interior systems.

Practitioners CAN:

  • accept mechanical systems (fourth pillar) are the “clean-up crew”, compensating for shortfalls in the first three pillars.
Close