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NC-v4 EQc5:Thermal comfort

Local discomfort Effects

Hi everybody,

It isn't clear to me how to document the local discomfort effects when I am under option 1 ASHRAE  standard 55-2010.

  1. ASHRAE 55 APPENDIX C states that the operative temperature may be assumed to equal the air temperature when the project meets four specific conditions. Is it acceptable to assume that my project does not have Radiant temperature asymmetry if the four conditions mentioned in ASHRAE 55 appendix C exist?
  2. Is it acceptable to say that there is no draft if the airspeed is less than 40 ft/min?
  3. Which cases shall I provide simulations to show the vertical air temperature difference? my understanding is that well-mixed ventilation does not have vertical air temperature difference but a displacement ventilation system.

Looking forward to hearing your answers to my questions. 

Best wishes.

 

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Fri, 12/20/2019 - 17:17

Note the discussion about documenting local discomfort effects in Section 6.2.3: "Local discomfort effects are difficult to calculate due to limitations in thermal modeling tools, but can be estimated with simplified assumptions. Local discomfort shall be addressed by, at a minimum, a narrative explanation of why an effect is not likely to exceed Section 5 limits. When a design has asymmetric thermal conditions (e.g., radiant heating/cooling, areas of glazing that are above 50% window-to-wall ratio, additional air movement, stratified displacement cooling), a calculation of related local discomfort effects shall be included. At a minimum, documentation shall identify the design condition analyzed for each local discomfort effect and any simplifying assumptions used in the calculation." 1. Yes, I think it would be reasonable to assume that if the four conditions in Appendix C are met, then radiant temperature asymmetry would not be a problem.  2. Not necessarily. ASHRAE 55-2010 removed the detailed draft calculations from ASHRAE 55-2004, but does establish a limit of 30 fpm for operative temperatures below 72.5 deg. F.  3. A displacement ventilation system is a common example of when calculations may be required for vertical air temperature difference. In most systems with well-mixed ventilation, a difference of 5.4 deg. F is unlikely and therefore calculations are unnecessary.

Wed, 01/22/2020 - 15:19

Tyler, thank you very much for your answers.

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