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Re: GBlist: definition of "Heating Season"
Jorg:
Heating degree days are always measured to some base temperature. The
total degree days for the year are then added up. In some climates, such
as Seattle, this means that many heating degree days even fall into summer
months.
In the US, the National Ocanic and Atmospheric Administration (NOAA) gives
annual degree day sums for various base temperatures, from 40 to 65 deg. F
for heating and from 4 to 70 deg F for cooling. Other sources give an 80
deg F base for cooling. The choice of base temperature is based on the
balance point of your building, the temperature at which a conventional
(closed) building changes froma need for cooling to a need for heating.
This temperature drops as internal loads from lights, people, and equipment
increase or as either solar gain increases or insulation of the envelope
increases. Our DD seasonal values are often based on 65 deg F, but almost
mo building built today balances at that temperature. A skin load ominated
( low internal load building may have a balance point of 55 deg F or lower.
55 deg F is a common assumption for well insulated houses. Commercial
buildings may have very low balance points. In some climates, heating is
never needed because of all the internal loads.
If a building is passively cooled, there is a floating zone between the
heating balance point and the cooling balance point.
Another thing to remember is that DD figures are based on averages from 30
years of data. Your particular year may vary significantly from the
average.
Also, the solar contribution(solar savings fraction--SSF) may be
subtracted from seasonal energy calculations: (1-SSF x DD base) x UA = E
Balcomb (Passive Solar Heating Analysis) gives values for a few canadian
locations at bases from 50 deg F to 70 deg F. Nothing for Calgary. Here
is data for deg F bases for Edmonton and Suffield:
Edmonton: D50:6318; D55:7587; D60:9048; D6510671; D70:12425
Suffield : D50:5513; D55:6649; D60:7953; D65:9423; D70:11045
(5/9) deg F day = 1 deg C day
Actually, I have been looking for variable degree day information for
Canadian locations, similar to the NOAA publication. Let me know if you
find a source.
Hopre this helps,
Mark DeKay
>After having calculated our total backup heating for the winter (in
>Kwh/DD/cubic M) based on what I thought constituted our heating season, we
>had a week of 26 DF weather followed by 15cm snow, followed by a week
>without sun and highs of 5 DC. Now I have to revise my heating season.
>What is the best
>definition of "Heating Season"? Does ASHRAE have one that can be used in
>any location? Would it be based on DD using 18 degree C as the base?
>Comments and definitions welcomed.
>_________________________________________________________
>Jorg Ostrowski, M. Arch. A.S. (MIT), B. Arch. (Toronto), Ecotect
> - living a conserver lifestyle & working in a sustainable home and office
>_________________________________________________________
>
>
>__________________________________________________________________
>This greenbuilding dialogue is sponsored by Oikos (www.oikos.com)
>and Environmental Building News (www.ebuild.com). For instructions
>send e-mail to greenbuilding-request@crest.org.
>__________________________________________________________________
Mark DeKay
Assistant Professor of Architecture
School of Architecture
Washington University
One Brookings Drive
campus box 1079
St. Louis, MO 63130 USA
dekay@arch.wustl.edu
Office: 201 Givens Hall
314.935.6282, 314.935.8520 (fax)
__________________________________________________________________
This greenbuilding dialogue is sponsored by Oikos (www.oikos.com)
and Environmental Building News (www.ebuild.com). For instructions
send e-mail to greenbuilding-request@crest.org.
__________________________________________________________________