Re: [TRNSYS-users] correct modelling of brick facade

[Ivan Flores Abascal <ivan.flores@ehu.es>]

Dear Leen:

When I analyze these types of façades, I treat the air cavity as a  
massless layer that provides a thermal resistance. The thermal  
resistance value can be obtained from the ISO 6946 standard. They are  
tabulated depending on the thickness, the heat flow direction and the  
ventilation rate.

According to this standard: “An air layer having no insulation between  
it and the external environment, but with small openings to the  
external environment, shall also be considered as an unventilated air  
layer if these openings are not arranged so as to permit air flow  
through the layer and they do not exceed
 - 500 mm2 per metre of length (in the horizontal direction) for  
vertical air layers,
- 500 mm2 per square metre of surface area for horizontal air layers.
NOTE Drain openings (weep holes) in the form of open vertical joints  
in the outer leaf of a masonry cavity wall usually conform with the  
above criteria and so are not regarded as ventilation openings.

Best regards

Ivan Flores

Lecturer of Heat Transfer

Department of Thermal Engineering / Departamento de Máquinas y Motores  
térmicos

Engineering School of Bilbao / E.T.S. de Ingeniería de Bilbao; EHU / UPV

Address: E.T.S. de Ingeniería de Bilbao, Alameda Urquijo s/n, 48013  
BILBAO, (Spain)

Phone: +34 946018214  Fax: +34 946014283


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