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

[RT]

On Mon, 21 Nov 2011 17:47:34 -0500, Reuben Deumling <9watts at gmail.com>  
wrote:

> On Mon, Nov 21, 2011 at 8:46 AM, RT <Archilogic at yahoo.ca> wrote:
>
>>  "negijiboo".
>
>
> or not. I did as you did, and depending on the distribution of the
> temperature you can have the HDD be several degrees off. Maybe I'm being
> way too precise here,

I know nuttin' about nuttin' on this so I'm just talking out of my hat  
really but I would venture that the importance of the degree of precision  
would depend upon what you are intending to do with the HDD/yr figure.

Me ?

I think "good enough for horse shoes and hand grenades" type precision is  
sufficient if using the HDD/yr figure in calculations for a particular  
location when trying to make decisions during the design process of a  
building for normal occupancies.

Why ? Because weather is so variable in this age of climate change that  
what happened over the course of even just the past 2 years is no  
indication of what is likely to happen this coming year.

In making design decisions, I would design for the worst conditions that  
have occurred and are likely to occur in the future (future being a best  
guess, using one's judgement) and include a factor of safety. Not an  
unreasonable approach given that for structural engineering design (Limit  
States Design), one allows a 25%

ie If the precise-as-the diameter-of-a-gnat's-peach-fuzz HDD/yr  
calculations result in a higher HDD/yr figure, then use that one in your  
calculations. If the horse shoes and hand grenades figure is higher, use  
that one.

In the end, I doubt that it would make much difference in the outcome of a  
design decision... or at least I can't think of any example of where it  
might matter.


-- 
=== * ===
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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