[Bldg-sim] calculating the mean monthly outdoor temp

[JRR]

John Ross wrote;

Using a mean monthly temperature ties the hands of innovative engineers 
in opportune climates.
In Northern Virginia I use an opening roof skylight to dump excessive 
solar gain in the late afternoon.
This operational variation is only practiced the last week of September 
to the second week of October
depending depending on  the particular year's weather

It would be appropriate to use mean monthly temperature for calculating 
long term Geothermal field
effects on the  other hand.......


Nathan Miller wrote:
> I'm no statistician, but I've always been dubious about that calculation.
> You are taking the mean of two means, which seems to be getting farther
> and farther from actual data.
>
> It also seems to punish some of the climates that are best suited for
> natural ventilation, since having cool nights significantly drops the
> acceptability limits. I assume they are pushing you to take advantage of
> night pre-cooling and thermal mass, but I find it curious that there are
> no allowable hours outside of the range. All of the pre-cooling in the
> world isn't going to help you keep the temperatures down during that one
> string of 90 degree days in the tmy2 file...
>
> Nathan Miller
>
> Senior Energy Engineer/Mechanical Engineer
>
> direct: 206.788.4577
>
> fax: 206.285.7111 
>
> -----Original Message-----
> From: bldg-sim-bounces at lists.onebuilding.org
> [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Chris Yates
> Sent: Friday, November 28, 2008 2:30 AM
> To: Building Simulation
> Subject: Re: [Bldg-sim] calculating the mean monthly outdoor temp
>
> 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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>>
>>     
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