cold war, cold weather...

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I haven't seen a reply yet to this, so here goes . . .

The oldest ASHRAE handbook on my shelf is a 1972 HOF (thanks Bob H.!).
Chapter 33 is Weather Data and Design Conditions. The reference list
includes these two primary sources:

Evaluated Weather Data For Cooling Equipment Design, Addendum No. 1,
Summer and Winter Data (Fluor Products Company, Santa Rosa, Calif., 1964).
Engineering Weather Data (Army, Navy, and Air Force Manual TM 5-785, 1963).

You can buy a copy of the 1958 edition of Evaluated Weather Data on amazon

I bet someone out there has a copy of the Engineering Weather Data
manual on a shelf. Some quick searching leads to this later online version.
which says:

"The Engineering Weather Data (EWD) and other products were developed by
the Air Force Combat Climatology Center (AFCCC). Data is provided for
approximately 800 stations worldwide. Intended to support design and
construction of DOD facilities, the format is slanted toward
professional engineers, but could have numerous other uses. "

Searching AFCCC leads here to a fascinating history.

"The mission of AFCCC is one of military applied climatology. We
collect, maintain, and apply worldwide weather data, creating
climatological products to strengthen the combat capability of America's
warfighters. AFCCC's support to America's warfighters has a long history."

And a fitting excerpt on the 75th anniversary of D-Day:

"There was probably no WWII operation, major or minor, that did not
include climatological input. The planning for every landing, mission,
and offensive, including the D-Day invasion in 1944 and the atomic
bombing of Japan, required extensive climatological preparation and

So, Chris, your impression appears correct. Weather data statistics were
motivated by military requirements (for better or worse), and marketing
cooling equipment.


p.s. The pages from the 1972 HOF are included in a digitized NBSLD
manual (one of the great mother programs of building simulation), pdf p.

Michael J. Witte's picture
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Wow. You know what Michael. I think you have the makings of an ASHRAE
journal atricle! I want to do something similar for CIBSE. I'd love to use
your findings.
On 5 Jun 2019 23:21, "Michael J Witte via Bldg-sim" <

Chris Yates2's picture
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I have a copy of the Engineering Weather Data
document (1978 version). (Thanks, Bob H).

And many other historical "weather data"
documents though not sure how many discuss heating/cooling design data.


Linda Lawrie2's picture
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Chris - Sure, go right ahead and write a joint article for CIBSE and ASHRAE.

I know ASHRAE is working on interviewing those with a long-time
perspective (old-timers) to document early ASHRAE work.
Jeff H - anything related to weather data happening in the history
effort? Maybe some members of the weather data TC would contribute.

Linda - Does the forward of Engineering Weather Data have any mention of
the motivation for that data? Is that where the concept of using 99%
etc. was first used?

Anyone out there have a copy of the Fluor Products publication? It was
cited as the source of the US design data in the 1972 HOF.
Evaluated Weather Data For Cooling Equipment Design, Addendum No. 1,
Summer and Winter Data (Fluor Products Company, Santa Rosa, Calif., 1964).

Michael J. Witte's picture
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At 08:05 AM 6/7/2019, Michael J Witte via Bldg-sim wrote:

It mentions 99%/97.5% (heating) and 1%/2.5%/5% (cooling).

The main first sentence says "This manual gives uniform engineering
weather data for winter heating design, heating degree days, summer
air conditioning design and criteria, for calculating energy
consumption estimates, and cooling degree days." (No reference
document given about those).

Supersedes (several documents from 1967).

Since this was 1978 publication -- I imagine the 1972 HOF might have
had something?

Linda - free repository of climate data for
building simulation

Linda Lawrie2's picture
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As the current chair of TC 4.2 Climatic Information, I feel obligated to
reply :-)

While I admire Chris' and your enthusiasm, I am pretty certain that the
design temperatures in the ASHRAE Handbook grew out of the needs of the
HVAC engineers going back at least to the 1940's for cooling, and even
much earlier for heating.? I'm hoping that Jeff? Haberl can clarify the
situation and have cc'd him on this e-mail to get his attention. I've
also cc'd the TC4.2 Group in case others remember more clearly the
history of ASHRAE design temperatures. If I were a betting man, I would
wager the HOF design temperatures came out of either the industry
(Carrier ?) or engineers within the predecessor societies AHVE, ASHE
that merged in 1959 to form ASHRAE, and that the? Air Force adopted it
in their publication, rather than the other way around. As Michael had
pointed out, the AF publication states that the design temperatures were
"intended to support design and construction of DOD facilities", with no
mention of use in military aviation.

It's funny how this almost off-the-cuff decision had endured and got
embellished to make it seem more hefty.? For example, in the 1960's
engineers got concerned about dynamic effects and so added on hourly
profiles for temperature, solar, wind, etc., to create an artificial
design day, and in the 1990's to accommodate climates with different
seasons (or no seasons!) the criteria was switched from? a seasonal 1%
to an annual 0.4%. Why 0.4% ?? Simply because the temperatures would
match the previous 1% seasonal? (I was in TC 4.2 at the time and
recalled those discussions).?? The evolution of ASHRAE Design Conditions
would seem also to make an interesting and informative paper.

As far as meteorology having an impact on military operations, I can
describe an old family story.? My father, Dr. Hsia-Chien Huang
was the Chief Meteorologist of China during World War Two.? He received
his Ph.D. at Caltech in the late 1930's studying with Dr. Irving Krick
. Dr. Krick was hired by
General Eisenhower to forecast the weather for the Normandy Invasion.
The details are in the web page so I won't describe them here, only to
say that I grew up hearing that Dr. Krick predicted the weather for the
invasion and that someone in the UK actually produced a play about this
incident. Since Dr. Krick sponsored my family to the US in 1955, I can
say that the only reason I'm in the US is due to meteorology!?? For the
oldtimers in TC 4.2, can you guess who picked up my family when we
arrived in Denver 64 years ago? Loren Crow,? who was then working for
Dr. Krick, as did my father afterwards.? Loren was very involved in TC
4.2 up until the early 1990s, having created the original WYEC files and
the CTZ files for California.? Gee, maybe all these deep personal
connections to meteorology might explain my late life pre-occupation
with weather data!


Joe Huang's picture
Joined: 2011-09-30
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Thanks Joe - I was hoping someone would chime in with more authority.
And a fascinating personal history - who knew?

Michael J. Witte's picture
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Thanks Joe. This is fascinating.

My understanding of the percentiles 0.4, 1.0, 99 & 99.6% design data was
that they covered everything except the coldest or hottest 35 or 87.6 hours
in a typical year. I need to double check my understanding. All I know is
that it seems to work the opposite way around if I use Excel's

Was the translation of the 1% to 0.4% based on the former being two seasons?
On 7 Jun 2019 21:20, "Michael J Witte via Bldg-sim" <

Chris Yates2's picture
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1 percent of 8760 = 87.6

On Sat, Jun 8, 2019, 6:03 PM Chris Yates via Bldg-sim <

Drury B Crawley's picture
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The 1%, 99% used prior to

Sent from my iPhone
Joe Huang
White Box Technologies
346 Rheem Blvd Suite 108D
Moraga CA 94556
(o) 1(925)388-0265
(c) 1(510)928-2683
yjhuang at

Joe Huang's picture
Joined: 2011-09-30
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I think my previous response was a tad short, so I'll elaborate :-)??? (What actually
happened was that I was composing my answer on my IPhone? that sent it out unexpectedly,
so I decided to wait until I got to the office where I'm in more control of the e-mail).


Yes, you're correct on both points.? The percentiles are of all the hourly values in the
long-term record, so 0.4% would mean there are? on average 35 hours at or above that
temperature over a year, and so forth.? The pre-1996 definition of 1% seasonal would be 22
hours at or above that temperature over 2208 hours from June through August.? If all the
hours above that temperature would occur only in those three summer months, the 1%
seasonal would correspond to 0.25% annual.? However,? there are almost always such hours
that occur outside of those months and since the frequency of occurrence varies greatly by
climate,? it's impossible to find an universal correspondence of annual to seasonal
frequencies.? For example, in Singapore where there is very little season variation in
temperatures, the 1% seasonal would be about the same as the 1% annual, or 88 hours over a
typical year, more than double the number of hours in a temperate climate. Because of
these inconsistencies and the awkwardness of having to define summer and winter in
different locations (here in San Francisco the hottest month is always September), ASHRAE
decided to change from seasonal to annual percentiles for the 1997 Handbook.? I was on TC
4.2 at the time, and what transpired with this switch was interesting and at times
humorous.? If we switch to annual percentiles, which percentiles should we use?? Engineers
are very attuned to "their" design temperatures, so we didn't want to create an uproar
with large changes in the design temperatures due to changes in the metric, but new metric
does not produce a one-to-one correlation to the old metric. In the end, the TC asked the
contractor to compare the temperatures at different annual percentiles to the old seasonal
percentiles, and use the annual percentiles with the best overall match, which turned out
to be 0.4%, 1%, and 2%? for the previous 1%, 2.5% and 5% seasonal percentiles.

There are many things in the ASHRAE design procedure that are similarly ad-hoc or
evolutionary, to use a better adjective :-) , which is why I tend to view it with a slight
grain of salt.? I've also talked to engineers and academics in other countries over the
years, and have that the ASHRAE design procedure is only one of several in the world.


Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 205A
Moraga CA 94556
yjhuang at for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"

Joe Huang's picture
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