EnergyPlus™ is a whole building energy simulation program that engineers, architects, and researchers use to model both energy consumption and water use in buildings.
Tianzhen, any reason that "Ratio of Frame-Edge Glass Conductance to Center-Of-Glass Conductance" should still have a min limit of 1.0 in the IDD?
Michael J. Witte on 28 March 2014 06:00 PM
Needs a new issue to request that the IDD limit be changed (see above note). Never got an answer back about this, but seems like it's needed.
Michael J. Witte on 17 June 2014 09:00 PM
Jean Marais
engineer
User
Posted on: 07 May 2014 09:49 AM
SOLVED:
1) The edge-of-glass to center of glass conduction ratio is also (like the
frame conductance) to be input in the idf without film coefficients. WINDOW
uses interior and exterior film coeff. of 30 and 8 W/m2K respectively in
all it's idf outputed results calculations to strip off the airfilms.
Except for the glazing U-value Ug, which must include the rated film coeffs.
2) The Uf input in WINDOW is the 2d equivalent rated U-value as per
American Norms (NFRC 100-2007 & ASHRAE HOF) which can differ very strongly
to the EU norm EN ISO 10077-2 used to calculate Uf. This is mainly due to
other inside outside temperature differences and inside outside film
resistances.
3) Although WINDOW may be used to produce the correct idf input data, it is
important that the user input to WINDOW is correct. The user can switch to
CEN norms for calculation of both the glazing buildup and the total
fenestration product to see if it matches up to his European datasheet.
However, inputs to WINDOW such as Uf must be as per american norms for an
American calculation and EU norms for a CEN calculation of the whole
fenestration product.
The Window U-value includes inside and outside film coefficients, but the
idf input for frame conductance does not include film coefficients. See
attached. Does this clear up the questions?
Mike
Thanks Mike, below is a copy of the conversation I am having with the
team at DesignBuilder.
"Hi Team, I'm chatting to Mike White about this at the moment. It also
concerns the glass to edge conduction ratio outputs from the WINDOW
outputs which is not equal to Uedge/Ug as I suspected.
I think we should consider the output file from WINDOW has an
effective (2D) frame conductance, as you say. The WINDOW input must
then be a linear conductance (which I thought was already supposed to
be the 2D effective conductance which one can get from THERM). I
still don't know why WINDOW does not show the frame effective U-value
in it's own GUI results (but instead the input value), but only in the
idf export."
On 28.03.2014, at 19:52, DesignBuilder Support wrote:
Jean,
I had a chat with Andy and we are thinking that these differences
between DB and WINDOW for the frame conductance could be related to
2-D conduction effects. In DB we have only 1-D, so we are not taking
into account the 2-D conduction effects.
in E+ (following the InputOutputReference.pdf), the effective
thermal conductance of the frame measured from inside to outside
frame surface (no air films) and taking 2-D conduction effects into
account. Obtained from the WINDOW program or other 2-D calculation.
1-Workaround
The workaround for now if the customers already have the frame
conductance from other software (e.g WINDOW) is adjusting the frame
thickness.
In your example model, if we change the frame thickness from 0.05 to
0.035 m we should get the same value of WINDOW.
DB exports frame conductance = 1.823 W/m2-K (0.05 m frame thickness)
DB exports frame conductance = 2.6 W/m2-K (0.035 m frame thickness)
2-Improvements
We thought to include an alternative option to overwrite the DB
calculation in the Openings tab -> Frame and dividers. Something
like in the figure attached.
mjwitte
commented
10 years ago
Helpdesk Ticket 9257
Tianzhen, any reason that "Ratio of Frame-Edge Glass Conductance to Center-Of-Glass Conductance" should still have a min limit of 1.0 in the IDD? Michael J. Witte on 28 March 2014 06:00 PM
Needs a new issue to request that the IDD limit be changed (see above note). Never got an answer back about this, but seems like it's needed. Michael J. Witte on 17 June 2014 09:00 PM
Jean Marais engineer User Posted on: 07 May 2014 09:49 AM
SOLVED: 1) The edge-of-glass to center of glass conduction ratio is also (like the frame conductance) to be input in the idf without film coefficients. WINDOW uses interior and exterior film coeff. of 30 and 8 W/m2K respectively in all it's idf outputed results calculations to strip off the airfilms. Except for the glazing U-value Ug, which must include the rated film coeffs. 2) The Uf input in WINDOW is the 2d equivalent rated U-value as per American Norms (NFRC 100-2007 & ASHRAE HOF) which can differ very strongly to the EU norm EN ISO 10077-2 used to calculate Uf. This is mainly due to other inside outside temperature differences and inside outside film resistances. 3) Although WINDOW may be used to produce the correct idf input data, it is important that the user input to WINDOW is correct. The user can switch to CEN norms for calculation of both the glazing buildup and the total fenestration product to see if it matches up to his European datasheet. However, inputs to WINDOW such as Uf must be as per american norms for an American calculation and EU norms for a CEN calculation of the whole fenestration product.
No user idf files