[Equest-users] FW: eQuest question on modelling interior surface between floors

[Chris Jones]

Thanks Brian.  I assume heat transfer between 
plenum and space has the same issue in LS-B, LS-C?

At 11:28 AM 28/09/2012, Brian Fountain wrote:
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>I had a question yesterday regarding heat 
>transfer through interior walls.  I think this 
>comes up on the list fairly frequently – why is 
>my LS-C (or LS-B) report showing no heat 
>transfer across internal surfaces when I know my 
>garage or attic is colder than the adjacent 
>spaces.  Is this heat loss really being 
>reflected in the model – and if so, why isn’t it in the LOADS reports?
>
>Here was my answer – (corrections & clarifications are welcome):
>
>What you are doing to model the effect of 
>insulating the floor between the garage and the 
>ground level is correct.  eQUEST will calculate 
>the heat loss across that interior surface floor 
>and show the impact of the insulation.  The main 
>issue is finding it.  I imagine you are looking 
>at the LS-C or LS-B report which show no 
>internal conduction.  The issue here is how the 
>calculations are sequenced in DOE-2.  In the 
>LOADS, we are calculating the envelope heat loss 
>then in SYSTEMS we are calculating the HVAC 
>response.  But, until the HVAC response is 
>calculated, we don’t know what the space 
>temperature is so we can’t calculate the 
>envelope heat loss as we don’t know the delta-T 
>between inside and outside.  So, for LOADS, we 
>give the space temperature an initial guess – 
>keyword Temperature in the SPACE.  By default, 
>all spaces have their temperature set to 70F – 
>this is why you see no internal heat loss in the 
>LS- LOADS reports as the temperature is the same 
>for all zones.  You could set the annual average 
>temperature down in the garage so that the heat 
>loss shows here but it is not that 
>important.  As long as in the zones, the keyword 
>SIZING-OPTION is set to ADJUST-LOADS then in 
>SYSTEMS, the actual space temperature will be 
>used to recalculate the heat loss.
>
>So, the heat loss is there – you can reassure 
>yourself of this by creating an interior wall of 
>nearly infinite resistance, apply it as a 
>parametric run, and see the space heating in the 
>adjacent zones go down.  You can also create 
>hourly reports that look at the parameters of 
>the zones.  One of the hourly variables (23) at 
>the zonal level is “Contrib to the zone load due 
>to conduction from adj zones (Btu/hr)”  -- this 
>is where you will see the actual hourly heat 
>loss using the actual hourly space temperature for the zones.
>
>I hope this helps clear up what you are 
>seeing.  Please feel free to ask more if I am not being clear.
>
>Kind regards,
>
>Brian
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 >>
Christopher Jones, P.Eng.
Suite 1801, 1 Yonge Street
Toronto, ON M5E1W7
Tel. 416-203-7465
Fax. 416-946-1005
email cj at enersave.ca