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# why there are two adaptive thermal comfort model equations?

I found two different adaptive thermal comfort model equations from de Dear et al's two papers.

1) Comfort operative temperature = 18.9 + 0.255*[mean outdoor daily effective temperature]

... from the paper

de Dear, R., & Brager, G. S. (1998). Developing an adaptive model of thermal comfort and preference. ASHRAE Transactions, 104(1), 145-167.

2) Tcomf = 0.31*[Ta,out] + 17.8

... where Tcomf means indoor comfortable temperature, and Ta,out means mean outdoor air temperature,

... from the paper

de Dear, R., & Brager, G. S. (2002). Thermal comfort in naturally ventilated buildings: revisions to ASHRAE Standard 55. Energy and Buildings, 34, 549-561.

I don't have access to the latest ASHRAE Standard 55-2013 now, so I don't know which one is actually adopted by ASHRAE.

Thank you!

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The second one is in the Standard.

It is not the transient outdoor temperature that is the independent variable, though. It is the "prevailing mean outdoor air temperature," which is a moving average with a window of at least 7 days and at most 30 days (or more if you use a more complex weighting scheme).

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Do you know why de Dear decided to "update" the regression equation from the one shown in his 1998 paper?

( 2015-07-04 08:07:49 -0600 )edit

From de Dear and Brager's 2002 E&B article: "The outdoor climatic environment for each building was characterized in terms of mean outdoor dry bulb temperature Ta,out, instead of the ET* index that was originally proposed in the first publication of the ACS [5]. The reason for the downgrade to a simpler outdoor temperature expression is that the theoretically more adequate thermal indices such as ET* require both specialized software and expertise that most practicing HVAC engineers are unlikely to possess."

( 2015-07-06 14:42:11 -0600 )edit

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