[Equest-users] BEPU space heating calculation

[Chris Jones]

Re equest and hand calcs.  I know a few people that actually use hand 
calcs to demonstrate where equest, ecotect and other simulation 
programs are coming up with incorrect answers.  Graham, care to illustrate?



At 08:38 AM 26/08/2010, Carol Gardner wrote:
>Let me take a crack at this. What John is saying is that eQUEST 
>takes into consideration all building components and their 
>interactions. You can't just pull out one and ask hey why doesn't 
>this match my hand calc? In fact, if you want eQUEST to match a hand 
>calc, you shouldn't be using it: use the hand calc.
>
>Carol
>
>On Wed, Aug 25, 2010 at 2:04 PM, Paul Riemer 
><<mailto:Paul.Riemer at dunhameng.com>Paul.Riemer at dunhameng.com> wrote:
>
>John,
>
>Internal gains figure into Ben 's approach by choosing a HDD number 
>based on a balance point temperature that is below the actual space set point.
>
>The balance point temperature is a theoretical temperature at which 
>the building does not require heating because the internal gains 
>offset the envelope loads.
>
>To say it accounts for solar gain is a stretch but hey it is just a 
>hand calc.
>
>Ben does not state which HDD base he chose, but there are published 
>values for temps like 55F, 60F, 65F etc.
>
>
>
>Ben,
>
>It is good you are checking your results but I would ask do you 
>believe your baseline model?  Try your HDD calc on the your building 
>U rather than the differential.  How does that gas consumption 
>compare to your baseline model heating gas consumption?
>
>Does a different HDD base fit your model better?
>
>
>
>If you think your baseline model is okay, when you changed the U did 
>you also change your shading coefficient?   A lower SC would 
>eliminate some passive solar heating.
>
>A daylighting interaction could be another possibility.
>
>
>
>You'll figure it out.
>
>Paul Riemer
>
>Dunham
>
>
>
>
>
>
>
>From: 
><mailto:equest-users-bounces at lists.onebuilding.org>equest-users-bounces at lists.onebuilding.org 
>[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of John Aulbach
>Sent: Wednesday, August 25, 2010 3:38 PM
>To: Ben Pressman; 
><mailto:equest-users at lists.onebuilding.org>equest-users at lists.onebuilding.org
>Subject: Re: [Equest-users] BEPU space heating calculation
>
>
>
>Ben - dumb question.
>
>
>
>How is internal load figuring into this equation? And solar gain from the sun?
>
>
>
>I NEVER get an exact U x A x dT savings, as eQuest takes ALL factors 
>into consideration.
>
>
>
>John R. Aulbach, PE, CEM
>
>Senior Energy Engineer
>
>Partner Energy
>
>1990 E. Grand Avenue, El Segundo, CA 90245
>W: 888-826-1216, X254| D: 310-765-7295 | F: 310-817-2745
>
><http://www.ptrenergy.com/>www.ptrenergy.com 
><mailto:%7C%20jaulbach at ptrenergy.com>| jaulbach at ptrenergy.com
>
>
>
>
>
>From: Ben Pressman 
><<mailto:bpressman at practicalenergy.net>bpressman at practicalenergy.net>
>To: 
><mailto:equest-users at lists.onebuilding.org>equest-users at lists.onebuilding.org
>Sent: Wed, August 25, 2010 1:32:04 PM
>Subject: [Equest-users] BEPU space heating calculation
>
>I have a Window Glass EEM run that upgrades the windows in a 1970s 
>school building from single-paned to double-paned, tinted, and 
>argon-filled; a decrease in U-factor from 1.04 to 0.35. The LV-D 
>report shows a decrease in building U-factor from 0.176 to 0.142 
>which, based on an HDD calculation:
>
>(0.176-0.142)*24hrs*(estimated HDD for my area)*A/eff = 1217 therms
>
>of savings, or 24.7% of the overall energy usage of my baseline 
>model. The BEPU report, however, shows almost no energy savings. How 
>can this be? Is there some way to see what schedule, or number of 
>degree days the calculation in the BEPU is using? Has anyone had 
>this sort of problem?
>
>Thanks,
>Ben
>
>-- Ben Pressman
>Project Engineer
>Practical Energy Solutions
>770 E. Market Street, Suite 250
>West Chester, PA 19382
>ph  610.430.1382
>cell  610.733.9518
>web  <http://www.practicalenergy.net/>www.practicalenergy.net
>
>
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>
>
>--
>Carol Gardner PE
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Chris Jones
14 Oneida Avenue
Toronto, ON M5J 2E3.
Tel.  416-203-7465
Fax. 416-946-1005

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