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<DIV><SPAN class=277554307-02042008 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Hi all,</SPAN></DIV>
<DIV><SPAN class=277554307-02042008 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">We are revisiting ventilated facades with cavity blinds in an attempt to minimise the fabric heat loads on a building. We are looking at internally and externally ventilated options. My experience in this area is limited to use of bulk airflow modelling (IES Apache or use of Arup's in house tools during the time I worked for them).</SPAN></DIV>
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<DIV><SPAN class=277554307-02042008 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">We have done some preliminary digging around to source the best software to determine average annual performance, bulk temperatures etc recognising that CFD will always have a place in understanding airflows and temperatures in more detail. Our current position is:</SPAN></DIV>
<DIV><SPAN class=277554307-02042008 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">1) We explored the possibilities with Energy+ and the ventilated facade / cavity model 2-3 years ago and were unable to generate results that we had confidence in. In skimming the version updates it does not appear that there has been further work on this module so we don't plan to go back to Energy+.</SPAN></DIV>
<DIV><SPAN class=277554307-02042008 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">2) We use IES Apache extensively but the blind inputs are indirect (unknown) rather than direct (known) properties and thus lead to uncertainty (see below)</SPAN></DIV>
<DIV><SPAN class=277554307-02042008 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">3) We were initially encouraged by the ICE software out of Sweden, but now understand that the blind inputs are similar to IES.</SPAN></DIV>
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<DIV><SPAN class=277554307-02042008 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">IES / ICE take as input for the blind the a SHGC modifier (1 - SHGC = the overall reflected component of the blind be it SW or LW radiation) along with the proportion of this which ends up as shortwave versus longwave radiation. There is also a U-Value / conductance modifier. The blind can be incident solar or time controlled like most programs.</SPAN></DIV>
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<DIV><SPAN class=277554307-02042008 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">We would prefer to input blind transmittance and absorptance (or reflectance) and let the software dynamically determine SHGC. Until you have an understanding of the temperature of the blind which is a function of incident solar radiation, ambient temperatures, cavity ariflow etc you won't know exactly what the longwave radiation component is of the SHGC. So the egg comes before the chicken ... . </SPAN></DIV>
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<DIV><SPAN class=277554307-02042008 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">In short the longwave component of the blind SHGC is a strong function of other dynamic or design variables and as such cannot be pre-determined with confidence in our professional opinion.</SPAN></DIV>
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<DIV><SPAN class=277554307-02042008 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Does TRNSYS or other overcome this limitation? </SPAN></DIV>
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<DIV><SPAN class=277554307-02042008 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Any suggestions? Any killer papers out there that have correlated longwave blind SHGC to different glazing & blind types and ventilation arrangements? for a variety of solar / ambient conditions ..... ? Anyone considering a PhD in the near future in this area :)?</SPAN></DIV>
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<DIV><SPAN class=277554307-02042008 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Regards,</SPAN></DIV>
<DIV><SPAN class=277554307-02042008 style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Graham</SPAN></DIV>
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<P class=MsoNormal style="MARGIN: 0cm 0cm 0pt" align=left><STRONG><SPAN style="FONT-SIZE: 10pt; COLOR: #2053b7; FONT-FAMILY: 'Arial Narrow'">Graham Carter</SPAN></STRONG><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: 'Arial Narrow'"> |<STRONG><SPAN style="FONT-FAMILY: 'Arial Narrow'"> Manager Sustainable Design</SPAN></STRONG> | <STRONG><SPAN style="COLOR: #2053b7; FONT-FAMILY: 'Arial Narrow'">Lend Lease design</SPAN></STRONG></SPAN></P>
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