Dear all Following the questioning here below I must admit that window characteristics specifications are not clear to me at the moment. What I usually have when I start modeling a building project is the Uw (whole window heat transmission factor), Ug (glazing), Sg (glazing solar factor) and CLR (clear ratio = glazing area / total area) values. What I usually don’t have is the Uf (frame) value and the time to model the window with WINDOW software. So here is the process I came down to. 1/ I chose the most similar window in TRNSYS window lib. 2/ I get the Ug value shown in TRNBUILD. First question: Is this the U value for the glazing only as the data file includes frame definition? Second question: The corresponding value in the data file is obtained at different ambient conditions (26.7°C e.g.) than the ones specified in the Norm (-18°C e.g.). Why is it so? 3/ I calculate the Uf value to aim at the desired Uw value. Third question: In TRNBUILD I must specify a “raw” value without convective and radiative contributions which are processed separately by TRNSYS. However the convective coefficients are said to be applied on both the frame and the glazing together which collides with the individual approach used in the Norm. To comply with what seems to be done by TRNSYS I thus use the following formula: Uf = [ 1 / (1/Uw - Rse - Rsi) – CLR*1 / (1/Ug - Rse - Rsi) ] / (1 - CLR) where Rse, Rsi are the whole surface resistances Rs = 1/ (hconv+hrad). Q°: Is it correct to consider the same Rs values for Uw and Ug (as it will be done eventually by TRNSYS anyway for the convective part)? 4/ I assess the solar factor difference between my “artificial window” and the reference value I have and specify it as an external shade factor in TRNBUILD. Here I use the Norm formula which is a little bit complicated so I will spare you the trouble. 5/ I eventually check the results of this rather intricate process with an elementary simulation test case. I use TRNSYS QUA variable with a few basic corrections and I typically get a value of Uw = 2.17 W/m2.K for a reference value of 2.1 which I consider satisfactory. Q°: Is there a way to get directly the Uw value calculated by TRNBUILD? Thank you very much for any answer you might have. Best -- Antoine Gautier antoine.gautier@solamen.fr Yujun TAO aleck1314 at yahoo.fr
hello users, I detected something strange about Window in Trnbuild. Or maybe I don't really understand.I find the calculation of Uw (U-value of the window), Ug (U-value of glazing) in Trnbuild is very scientific like they depend the outdoor temperature, the wind and the insolation. But these values are not clearly showed in Trnbuild, because I found the value (U-value of glazing) showed in the "window" was taken frow the files "W4-lib" or "Prgwin" in following location (outdoor temperature=26.7°C°, Solar (W/m².K)=0, WdSpd(m/s)=6.71, hcout, hrout, hin = (respectively) 25.47, 3.18, 6.89).You can find in the attached document with the location I indicated. It's not taken from the description location at the bottom of W4-lib or Prgwin files, neither from the head of Prgwin file.So I want to know curiously in the condition of european norm (CEN), how you defined a window and checked it (Ug, Uw) that you expected. Or more far in every different norm.Because the U-value in these descriptions is Uw (total window) said in the tutorial of window5, So for me, this value isn't useful because we can change the frame in the dialogue of"window". It's only useful for me when it's Ug and showed in the glazing in the dialogue of "window"(Trnbuild). I don't know if the TRNSYS 17 can do it.Second question is about g-value,I don't know where is g-value from, because the two values (middle of description of one window, bottom of W4-lib, Prgwin files) are the same. If it's like U-value said in the tutorial of window5, so it's should be used for total window, not for glazing.After all, for me, the indication of U-value, g-value of window in Trnbuild of TRNSYS 16 is strange and not according to the Norm (International, etc.), I want to know your experiences.Aleck |