[Bldg-sim] Balance point temperature for houses

[Glenn Haynes]

Hussein,

If my understanding on this issue is clear, then for heating it is the
statistically-determined ODB temperature at which the heating load on a
building approaches zero.  I agree with Mr. Bishop about 65F being
outmoded because I have studied both short and long term end-use metered
data and performed the regressions for single family detached residences
in Florida and New England (USA), both for old and new homes.

This balance point may be somewhat useful on a global basis in analyzing
the heating performance characteristics of typical homes, but for
individual homes the variance can be large, with most homes falling
within the range of about 50 to about 65 degrees F, and a few homes
beyond those limits.  The "tighter" the home, the lower the balance
point.

The balance point will also vary with time of day as the internal and
solar heat gains vary (say, from daytime to nighttime).

If you are looking for an overall degree-day (from daily average
temperatures) base, I would recommend something on the order of 55
degrees F for newer homes and 60 for older homes.  These will put you
closer to reality for average homes.  If you define degree-days from
hourly data as degree-hours per day divided by 24, you will need to use
even lower base temperatures (around 50) for heating and higher (around
70) for cooling.

I wish you good luck with such a "slippery" number, and I hope this
helps.  There really are no precise numbers to offer you for specific
applications.  And I do not recommend applying these numbers or this
method to large commercial buildings at all.

Glenn Haynes, PE
RLW Analytics, Inc.
Middletown, CT

-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Bishop,
Bill
Sent: Wednesday, May 07, 2008 9:29 AM
To: Abaza Hussein; equest-users at lists.onebuilding.org;
bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Balance point temperature for houses

Hussein,

I'll admit that I didn't even know what the balance point temperature
was.  I did some quick internet research and found this resource:

http://arch.ced.berkeley.edu/vitalsigns/res/downloads/rp/balance_point/b
alance_point_big.pdf

There is a lot of information about building heat gains and losses and
how degree days are calculated.  It mentions on p.55 that the 65F number
was determined in the 1940s, and that newer, better insulated homes have
a lower balance point, but it doesn't suggest a number.

William Bishop, EIT, LEED(r) AP | Pathfinder Engineers LLP
Mechanical Engineer

3300 Monroe Ave., Suite 306 
Rochester, NY  14618
TEL (585) 218-0730 Ext. 114
FAX (585) 218-0737 
bbishop at pathfinderengineers.com
 
www.pathfinderengineers.com
-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Abaza
Hussein
Sent: Tuesday, May 06, 2008 3:53 PM
To: equest-users at lists.onebuilding.org; bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Balance point temperature for houses

Could you please help. Is there any recent data or survey about the
balance
point temperature of homes in the US. Is the 65F still applicable?
I appreciate any input.
Dr. H. Abaza
ECU


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