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[EnergyPlus_Support] CTF Algorithm for Heavyweight Construction



Reference:
Investigation of the Accuracy of Calculation Methods for Conduction Transfer Functions of Building Construction
 
Dear All,
 
I am working in a simulation of a historic building (with 70 thermal zones) in Porto Alegre city, south of Brazil.
The building was constructed in the beginning of 1900.
 
It´s a building with heavyweight walls. The wall thickness in the 1st floor is (60 / 65) cm, in the 2nd floor is (50 / 55 cm) and the 3rd floor is (40 / 45 cm). The wall layers are constructed basically of bricks (10 cm) and stucco (2,5 cm).
 
My question is regard with the method for calculating the CTF used in EnergyPlus for heavyweight constructions. 
I have read some scientific articles which present the numerical methods used to calculate the CTF.
The more indicated to calculate the CTF for heavyweight constructions is the Frequency-domain Regression Method, according to the reference above.
EnergyPlus uses the State-space Method. This method, according to the reference, may causes numerical divergences compared to analytical solution obtained, depending on the Fourier of the simulation (time step, thermal resistence and capacity).
 
Please, I would appreciate to know what is the suitable method to calculate the CTF for heavyweight constructions.
/1/ Can I use the State-Space Method for this simulation or the Difference Finite Method (CondFD) is more indicated?
/2/ What is the State-space Method working envelope? 
 
I have already simulated the building with CTF algorithm and the outcomes seem reasonable for the first analysis.
I also simulated with CondFD algorithm and the results of DX Coil Total Cooling (maximum value within the design days for each zone) differ up to 20% less from the values obtained by CTF.
 
Thank you in advanced.
 
Best regards,
 
Adriano Carotenuto.
Porto Alegre - Brazil
 
Reference uploaded in link below:
http://tech.groups.yahoo.com/group/EnergyPlus_Support/files/CTF.ZIP
 
 
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