<html><body><span style="font-family:Verdana; color:#000000; font-size:10pt;">My program does not claim to do the total package - people, ventilation, lights, etc... It is strictly limited to the building envelope. I don't know where you people get this notion of averaging max and min hours ~ I use the total cooling and heating bin hours, just as prescribed by the DOE in their standard assessments - made after evaluating hundreds of different kinds of buildings, and devising a working model. We're talking apples and tangerines here - I'm using a model developed by the DOE that was used exclusively from 1970 until the late 90's. If it was good enough for everybody for those twenty years, it's good enough now ~ if you use it for the intended purpose, to model the building envelope. Sure I could add nomographs for infiltration, people, etc etc etc until it's so complicated only a person with a Masters Degree in Energy Management could understand it. That's not my purpose - we're going back to the stripped down V-8 that a back yard mechanic could maintain thirty years ago, not the hyper electronic fuel injected hybrids we have today - that cost ten times as much and get the same fuel economy.<br><br>BC<br><br>
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-------- Original Message --------<br>
Subject: Re: [Bldg-sim] calculating the mean monthly outdoor temp<br>
From: Chris Yates <Chris@zed-uk.com><br>
Date: Fri, November 28, 2008 3:29 am<br>
To: Building Simulation <bldg-sim@lists.onebuilding.org><br>
<br>
There is a small difference between the arithmetic mean of the monthly <br>
mean max and min and the overall arithmetic mean of 720 hours of weather <br>
data. Like you say, it's probably a legacy from the old pen and paper days.<br>
I've heard that some would use occupied period only to calculate the <br>
mean. However, I can not find any reference in the text of A55 to <br>
justify this. Being able to average the warmer occupied hours would make <br>
things a whole lot easier - even the 80% acceptability temperature can <br>
regularly be lower than the summertime peaks. It's a tough call for <br>
natural ventilation.<br>
<br>
Many thanks<br>
<br>
Chris<br>
<br>
Joe Huang wrote:<br>
> The cited method sounds like a carry-over from when stations reported <br>
> only max/min temperatures.<br>
> If hourly data is available, why wouldn't you just calculate the mean <br>
> of all the temperatures ?<br>
><br>
> Joe Huang<br>
> White Box Technologies<br>
><br>
> ----- Original Message ----- From: "Chris Yates" <Chris@zed-uk.com><br>
> To: "Building Simulation" <bldg-sim@lists.onebuilding.org><br>
> Sent: Thursday, November 27, 2008 1:58 PM<br>
> Subject: [Bldg-sim] calculating the mean monthly outdoor temp<br>
><br>
><br>
>> For the purpose of acceptability limits, can anybody cite any <br>
>> guidance on calculating the mean monthly outdoor temperature? I've <br>
>> read ASHRAE 55 and it states: "mean monthly outdoor temperature is <br>
>> the arithmetic average of the mean daily minimum and the mean daily <br>
>> maximum outdoor (dry bulb) temperature for the month in question."<br>
>> Thanks<br>
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><br>
><br>
><br>
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