RE: [EnergyPlus_Support] Rooftop outdoor air temperatures

["Jim Dirkes jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx>]

Thanks again to all who have provided insight on this topic!

I think Joe has “hit the nail on the head”. 

·�������� It is my supposition that the near-roof temperature, especially for a large roof, is substantially warmer than elsewhere at the local site.  That is unproven L.

·�������� The only outdoor temperatures I have in an energy model for the local site are the values in the weather file.  The local site and the weather file’s site may be miles / kilometers apart, so there is no assurance that they will match. (Almost certainly they will not match.)

·�������� I recognize that a reflective roof will be cooler than the same roof with lower reflectivity, and probably that will also be true for the near-roof temperatures.

·�������� I was hoping to capture some measure of how much warmer than the local site the near-roof temperatures are because of the roof material’s influence.  (e.g., is Tnear-roof > Toa_TMY?)  Craig’s paper shows measurements only on the roof, so it seems that I’ll have to wait for that research to be conducted!

·�������� I’ll stop thinking about this for now, but on the next few commissioning or retro-commissioning projects, we’ll try to collect data from air handler outdoor air inlets and compare to the weather station during day, night, sunny and cloudy days.  It will amount to only anecdotal information, but it might prove interesting and provide some more insight.

Thanks!



James V Dirkes II, PE, BEMP, LEED AP
<http://www.buildingperformanceteam.com/>www.buildingperformanceteam.com
Energy Analysis, Commissioning & Training Services
1631 Acacia Drive, Grand Rapids, MI 49504 USA
616 450 8653



From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
Sent: Tuesday, July 22, 2014 5:11 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] Rooftop outdoor air temperatures





Jim,

I think you're mixing up two different questions:
(1) meso-scale air temperature differences between the airport and the local site
(2) microclimate air temperature differences between the roof and elsewhere at the local site.