[Bldg-sim] [Equest-users] Roof Conduction Load

[Jeremiah Crossett]

Joe, Just wondering,  given your expertise how would you compare this to
the heat balance method.., and what do you think is more realistic?

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*Jeremiah D. Crossett  | Senior Analyst  |  Phase Change Energy Solutions*
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120 E. Pritchard St.  | Asheboro, NC 27203  | Mobile 503-688-8951
www.phasechange.com
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On Mon, Aug 19, 2013 at 6:14 PM, Joe Huang <yjhuang at whiteboxtechnologies.com
> wrote:

> **
> Just to repeat what David and Rodrigo have already sad, DOE-2 calculates
> conduction loads in a two step process. In LOADS, a constant reference
> temperature is specified, which DOE-2 uses to calculate the amount of heat
> flow through the surfaces. This is the LOADS loads summarized in the LS-E
> and LS-F reports.  In SYSTEMS, DOE-2 calculates the true temperature of the
> zone based on the loads passed from LOADS, as well as the actions of the
> HVAC system.  In the course of this calculation, the heat flows ("loads")
> from LOADS are adjusted, but this is not done surface by surface, but in
> total using the so-called "Zone Conductance" times the difference between
> the actual zone temperature and the reference temperature used in LOADS.
> At this point, heat flows through internal walls are also considered, using
> the  difference between this hour's zone temperature and the previous
> hour's zone temperature of the adjacent space, e.g., the Attic or Plenum.
> If you are interested in this number, I believe it can be extracted in an
> hourly report.
>
> In reference to Rodrigo's question, I don't see any benefit in forcing a
> heat flow between the room and the attic by using different reference
> temperatures.   You will simply get a constant heat flow at that
> temperature difference throughout the simulation. In reality, attics are
> generally colder than the room in the winter and warmer than the room in
> the summer, so the derived heat flow with this temperature difference
> doesn't get you any closer to reality, in my opinion.
>
> Joe
>
> Joe Huang
> White Box Technologies, Inc.
> 346 Rheem Blvd., Suite 108D
> Moraga CA 94556yjhuang at whiteboxtechnologies.comhttp://weather.whiteboxtechnologies.com for simulation-ready weather data
> (o) (925)388-0265
> (c) (510)928-2683
> "building energy simulations at your fingertips"
>
>
> On 8/19/2013 12:05 PM, David Wood wrote:
>
>  Hi All,
>
>  The LS-C report comes from the LOADS simulation portion of DOE 2.2. The
> plenum reference temperature used in LOADS is adjusted in the SYSTEMS
> portion of the program and the loads in the spaces adjacent to the plenum
> are corrected
> correspondingly.
>
>  Dave Wood
>
>
> On Thu, Aug 8, 2013 at 8:58 AM, Rodrigo Cerqueira <
> rodrigo.cerqueira at mra.qc.ca> wrote:
>
>  Hi,
>
> This happens because the load calculation is made with a fixed temperature
> (see picture). All the spaces, include plenum zones, have the same
> temperature by default (70°F). So, all roof load appears in the plenum
> spaces. To considerate the roof load, you have to change this temperature
> in plenum spaces and a part of roof load will appear like "internal surface
> conduction". But I'm not sure if this is a good practice. Maybe someone
> else has an opinion about that.
>
>
>
>
>
> *Rodrigo Cerqueira, *ing. jr, M.Ing.* *
>
> *Simulation énergétique *
>
>
>
> [image: signatureCouriel]
>
>
>
>
>
>
>
> *De :* equest-users-bounces at lists.onebuilding.org [mailto:
> equest-users-bounces at lists.onebuilding.org] *De la part de* Bhartendu
> Awasthi
> *Envoyé :* 8 août 2013 06:35
> *À :* equest-users at lists.onebuilding.org; bldg-sim at lists.onebuilding.org
> *Objet :* [Equest-users] Roof Conduction Load
>
>
>
> Hi All,
>
>
>
> I am doing an energy simulation model in eQuest. I noticed that the load through roof conduction in LS-C is zero where as in LS-B (for plenum space) it is showing some load.
>
>
>
> As per my understanding this load should appear in LS-C also.
>
> Also, if I reduce the U value of the roof, the load through roof reduces and can be accounted in LS-B only (plenum space).
>
>
>
> Refer attached LS-C and LS-B reports.
>
> Any help will be appreciated.
>
>
>
>
>
> Thanks & Regards
>
>
>
> Bhartendu Awasthi
>
>
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>
> --
>  Regards,
>
> David S. Wood
> Principal
> Wood, Byk & Associates
> office:    610.347.0710
>  mobile:  610.247.1208
>
>
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