[Bldg-sim] calculating the mean monthly outdoor temp

[Chris Yates]

There is a small difference between the arithmetic mean of the monthly 
mean max and min and the overall arithmetic mean of 720 hours of weather 
data. Like you say, it's probably a legacy from the old pen and paper days.
I've heard that some would use occupied period only to calculate the 
mean. However, I can not find any reference in the text of A55 to 
justify this. Being able to average the warmer occupied hours would make 
things a whole lot easier - even the 80% acceptability temperature can 
regularly be lower than the summertime peaks. It's a tough call for 
natural ventilation.

Many thanks

Chris

Joe Huang wrote:
> The cited method sounds like a carry-over from when stations reported 
> only max/min temperatures.
> If hourly data is available, why wouldn't you just calculate the mean 
> of all the temperatures ?
>
> Joe Huang
> White Box Technologies
>
> ----- Original Message ----- From: "Chris Yates" <Chris at zed-uk.com>
> To: "Building Simulation" <bldg-sim at lists.onebuilding.org>
> Sent: Thursday, November 27, 2008 1:58 PM
> Subject: [Bldg-sim] calculating the mean monthly outdoor temp
>
>
>> For the purpose of acceptability limits, can anybody cite any 
>> guidance on calculating the mean monthly outdoor temperature? I've 
>> read ASHRAE 55 and it states: "mean monthly outdoor temperature is 
>> the arithmetic average of the mean daily minimum and the mean daily 
>> maximum outdoor (dry bulb) temperature for the month in question."
>> Thanks
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