Thanks a lot for your detailed answer Marion. I actually got confused by the name of TrnBuild variable “External Shading factor” which I thought referred to radiation transmission factor and not to fraction of occultation (shdout in the formula I suppose). I understand from your explanations why the additional thermal resistance is also lower than expected (only affects glazing which is kind of surprising though). (PS : I also thank you for your interest in my idea of generating 3D data with third party software. I send you an example of DesignBuilder idf as soon as I have a moment). Thanks for all -- Antoine Gautier antoine.gautier@solamen.fr De : Marion Hiller [mailto:hiller@transsolar.com] Dear Antoine, looking at the calculation, it the resistance is always active when the shading is active. Maybe you confused due to the influence of the frame? The u-value of the frame is not influenced by the additional resistance of the shading. The NTYPE 50 UWIN is calculated of three different parts: a) Centre of glass b) Edge of glass (influenced by the spacer) c) Frame The Uglas (centre of glass and edge of glass) without the inner and out outer heat transfer is calculated by Redge=(1/alfain+(rshdin*shdin)+1/uedge . +(rshdout*shdout)+1/alfout)/fe Rcenter=(1/alfain+(rshdin*shdin)+1/ucentr . +(rshdout*shdout)+1/alfout)/fg Rges=Redge*Rcenter/(Redge+Rcenter) UGLAS=1/(Rges-1/alfain-1/alfout) Then the frame is included: UGL(N)=UGLAS* (1.-FFRAM)+UFRAM*FFRAM ! total window u-value without inner and outer heat transfer Finally the NTYPE 50 is calculated by: CASE (50) ! u-value of window (glass+frame)with standard inner and outer heat trasnfer coefficients IF (HO.GT.30.) RO=0.04 IF (HO.LT.0.005) RO=0.0 IF ((HO.LE.30.).AND.(HO.GE.0.005)) RO=0.13 UGLK=1./(1./(UGL(NWI)/3.6)+0.13+RO) ENDIF OUT(IOUT)=UGLK*3.6 Best, Marion Dipl.-Ing. Marion Hiller Geschäftsführer: Dipl.Ing. Matthias Schuler, Dipl.Ing. Thomas Auer, Dipl.Phys. Stefan Holst, Prof. Dipl.-Ing. Bleicher Von: Antoine Gautier [mailto:antoine.gautier@solamen.fr] Dear all I use the surface output Uwin to assess the thermal impact of an external shading device. As you know the thermal properties entered for the shading devices are effective only if a shading device is actually defined for the window in the zone description. I get the following results whereas I specified DeltaR = 0.06 m2.K.h/kJ in input. Does anybody understand this better than I do? i.e. why does the shading factor modify the thermal impact though the shading device is only active during periods of time with zero irradiation? Why do I not get the expected DeltaR in output but half the value? Shading factor - Uwin w/o shading - Uwin with shading [kJ/h.m2.K] - DeltaR [m2.K.h/kJ] 1 - 4.93 - 4.22 - 0.034 0.75 - 4.93 - 4.36 - 0.027 Thanks for your help -- Antoine Gautier antoine.gautier@solamen.fr |