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Re: [TRNSYS-users] low energy consumption buildings

Hi Christophe,
The transfer function method can be used for low energy buildings.  However, the accuracy of TFM becomes more of a question when you are modelling high mass buildings.  Many of the commercial software that are available have accuracy issues with modelling high thermal mass buildings. Different modelling techniques, such as that used in ESP-r should model high mass buildings more accurately.
A good question, which is not often reported is what levels of thermal mass can TFM models accurately model, and how much is the accuracy affected by using these methods in massive buildings.  If the accuracy is only affected by say +/- 5%, then this could acceptable considering all the other sources of uncertainty present.  

I would suggest reading the following article that debates the accuracy of current TFM models to accurately simulate high mass, historical, European buildings:

Beccali, G., et al. Is the transfer function method reliable in a European building context? A theoretical analysis and a case study in the south of Italy. Applied Thermal Engineering 25 (2005) 341-357

Rémi


-----Original Message-----
From: trnsys-users-bounces@engr.wisc.edu
To: trnsys-users@engr.wisc.edu
Sent: 23/11/2006 6:47 AM
Subject: [TRNSYS-users] low energy consumption buildings

Dear TRNSYS Users,
 
I would like to have an expert advice from TYPE 56 users and developers.
Thermal transfers trough walls are based on the Transfer Function Method
developed by Mitalas (cf. TRNSYS Manual, volume 6, § 2.1.6). What are
the limits of this method ? Is it suitable for very high insulated walls
(for example 20 cm of polystyrene over 16 cm of concrete) ?
 
Context of my question : In France, we are working on two big projects
of very low energy consumption buildings. We prescribe the use of
dynamic simulation as a conception tool because it's a very useful tool
to estimate heating energy consumption and summer comfort. We're hearing
some critics about TRNSYS, some says it is not suitable to these kind of
buildings. So, we would like to be sure of our software.
 
Thanks a lot,
Christophe.


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