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John Ross wrote;<br>
<br>
Using a mean monthly temperature ties the hands of innovative engineers
in opportune climates.<br>
In Northern Virginia I use an opening roof skylight to dump excessive
solar gain in the late afternoon.<br>
This operational variation is only practiced the last week of September
to the second week of October<br>
depending depending on the particular year's weather<br>
<br>
It would be appropriate to use mean monthly temperature for calculating
long term Geothermal field<br>
effects on the other hand.......<br>
<br>
<br>
Nathan Miller wrote:
<blockquote cite="mid:008301c953d7$f42c7c80$dc857580$@com" type="cite">
<pre wrap="">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: <a class="moz-txt-link-abbreviated" href="mailto:bldg-sim-bounces@lists.onebuilding.org">bldg-sim-bounces@lists.onebuilding.org</a>
[<a class="moz-txt-link-freetext" href="mailto:bldg-sim-bounces@lists.onebuilding.org">mailto:bldg-sim-bounces@lists.onebuilding.org</a>] 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:
</pre>
<blockquote type="cite">
<pre wrap="">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" <a class="moz-txt-link-rfc2396E" href="mailto:Chris@zed-uk.com"><Chris@zed-uk.com></a>
To: "Building Simulation" <a class="moz-txt-link-rfc2396E" href="mailto:bldg-sim@lists.onebuilding.org"><bldg-sim@lists.onebuilding.org></a>
Sent: Thursday, November 27, 2008 1:58 PM
Subject: [Bldg-sim] calculating the mean monthly outdoor temp
</pre>
<blockquote type="cite">
<pre wrap="">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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