[Greenbuilding] HDD and how they are calculated (daily avg. vs hourly avg)

[RT]

On Sun, 20 Nov 2011 11:31:14 -0500, Reuben Deumling <9watts at gmail.com>  
wrote:

> My understanding is that NOAA simply averages the high and low  
> temperature in a 24 hour period and subtracts that average from 65F.But  
> if one were to  say use hourly data, the resulting HDD figure would be  
> different. How  much different I don't know.


Apologies in advance if this response seems scatter-brained (or more than  
usual for me), excuse being that I just buried my 100 year-old Mom (who  
had been in my care in recent years) yesterday.

I would offer that the HHD data that is "out there" is good enough for  
most, if not all people on this list, who I would ass-u-me are using the  
numbers to assist them at the design stage of a proposed building.

I suppose a reasonable analogy might be like buying a pair of trousers.

One selects a certain waist size, fully cognisant of the fact that there  
will be hourly, daily or yearly variations in the actual waist measurement.

One person's approach might be to select a waist size in anticipation of  
eventual expansion -- another might select "just barely fits now" in  
anticipation (or perhaps hope) of eventual waist shrinkage -- another  
might simply select an elastic waistband... point being that the actual  
number is a necessary point of departure, for without doing so, one would  
be bottomless.

But back to calculations in which one would use an HDD figure ...

Even though most of the "official" data is typically for 65 degF  
set-point, one can and does include a correction factor to accommodate the  
desired design temperature (ie typically 72 degF).


-- 
=== * ===
Rob Tom
Kanata, Ontario, Canada
< A r c h i L o g i c  at  Y a h o o  dot  c a >
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