[EnergyPlus_Support] Sinusoidal data and ISO 13786

["FrancescoP" <direzionecontraria@xxxxxxxx>]

I am trying to test a very simple model considering periodic, sinusoidal weather data. I am considering different kind of walls.
The weather data file and two .idf files are available here:
http://tech.groups.yahoo.com/group/EnergyPlus_Support/files/Sinusoidal%20weather%20data/

In  ext ins.idf  I modelled walls with concrete on the internal side and insulation on the external side.
As you can see in the picture http://imageshack.us/photo/my-images/33/extins.jpg/ for variables relative to the inner side of the wall convergence is achieved only after some weeks. 

In  lowU highC.idf   I modelled walls having low thermal transmittance and high thermal inertia. In that case the variables relative to the inner side of the wall don't have a sinusoidal trend. See picture http://imageshack.us/photo/my-images/402/lowuhighc.jpg/
 Is there a convergence problem?

For all the models I have used both Conduction Transfer Functions (CTF) and  finite differences and the results seem similar.

With other kinds of walls convergence was achieved in the first days of the simulation and the trends were sinusoidal.
Does it mean that for some walls the results can be unreliable? How could these problems be avoided?

I compared the "decrement delay" [in hours] of EnergyPlus with the results of spreadsheet based 
 ISO 13786 "Thermal performance of building components -- Dynamic thermal characteristics -- Calculation methods". The decrement delay is defined as the time lag between the timing of the external temperature peak and the peak heat flow out of the internal surface.  I called "EP CFT" the results that I got with the CFT method and with "EP CFD" the results that I got with CFD method. The values are:

1. Walls with high U and high C
ISO 13786:    7,84 h 
EP CFT:          6,34 h
EP CFD:         6,30 h

2. Walls with high U and low C
ISO 13786:    0,27 h 
EP CFT:          0,0 h
EP CFD:         0,00 h

3. Walls with low U and low C
ISO 13786:    4,02 h 
EP CFT:          4,7 h
EP CFD:         4,25 h

4. Walls with concrete and external insulation
ISO 13786:    10,0 h 
EP CFT:          8,3 h 
EP CFD:         about  8h

5. Walls with concrete and internal insulation
ISO 13786:    9,35 h 
EP CFT:          8,3 h
EP CFD:         about  8h


Any comment, please?
With Regards
Francesco Passerini



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