[esp-r] Window u-value temperature dependency in ESPr

[Francesco Frontini]

Dear ESP-r users,

I have a question regarding how ESP-r calculates the properties of a glass
unit (for example a double glaze unit with argon gap).

I red several discussions about the capability of ESP-r of reading and
importing WIS or Window data file, but for me is not clear which kind of
data espr effectively read.

My knowledge is that, when we specify a glass construction we have to give
the resistances of the air gap between the glass panes (that is a fix value)
in the construction library and then define the optical properties in the
optic database (ESPr ask for the angle dependence absorptances of the
different panes and the angle dependence transmittance of the different
panes). That´s all! Am I wrong?

Now comes the question?

How does ESPr calculates the temperature dependency of the air (or gas) gap
resistance between the panes? It is not possible to define the emissivity of
both glass pane surfaces?



I know that TRNSYS uses the Window 4 model (but, if I correctly remember,
TRNSYS is not able to consider not standard emissivities for the outer
surfaces).



I have this question because I am modelling a family house room under a
tilted roof. The window is a roof window (like Velux). I think that, for
such cases, it is relevant to model correctly the temperature dependency
(also the wind dependency) of the gas-gap resistance.



Any help is appreciated.
Francesco

-- 
Dr. Francesco Frontini, MEng PhD in Buildings Engineering

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Fraunhofer Institut für Solare Energiesysteme ISE
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M2:    [+49] (0)1522-1624691

Phone: [+49] (0)7614588-5358
FAX:   [+49] (0)7614588-9358

@1: francesco.frontini at ise.fraunhofer.de
@2: francesco.frontini at polimi.it
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