What is the correct value for Pfd in Frames

[Michael Donn]

Kia ora tatou

This is a follow on from a query about calculating reliable  Window R-values https://groups.google.com/g/berkeley-lab-window/c/C1LZ3UWECZA 

I am trying to represent the appropriate R-value for windows with different frames, and glazing choice. I am also trying to ensure that, when I teach people to use these Pfd values, that they can understand how they differ from the values in the Building Code that they must comply with.  

The New Zealand Building (Energy) code proposed change is that no-one  will be able to state they have followed a list of complying component R-values to prove compliance. A heat loss calculation or a  simulation will be necessary. Getting the right input values just became a whole lot more critical.

I am getting radically different data than the New Zealand code data. My aim is to encourage ALL modellers to use the appropriate frame dimensions and spacer values for multiple glazing units to derive R-value, Solar Heat Gain Coefficient, and Visual Transmittance.  When I was trying to determine what to do about what the local industry describes as  "Improved" spacers, I looked more carefully at the Window Frames in Window. Below is what I came up with. I was keen to get the Pfd areas correct to ensure that, within the same "hole in the wall" in EnergyPlus we were modelling how much solar gain might actually get through, dependent on the solid vs transparent AND the VT or SHGC for the glass.

I set this aside for a while, but I am returning to it out of concern to understand what I might be doing wrong, prior to making a public submission on the Current setup of the Building Code Energy Performance requirements (28 Feb deadline).

I have been through the window frame options typically available in New Zealand that must be behind these numbers. The Building Code Window R-values are below.

Even allowing for their different definition of a "standard window", I cannot replicate their values with my Pfd inputs. One can clearly get closer with  with different frame area values, but this seems wrong, unless I am misunderstanding the frame Pfd data completely?

  

:

These R-values have been calculated for a suite of "representative" house window sizes - and averaged and the range of sizes available is not published yet: the calculations were apparently done using Flixo (https://www.flixo.com/products/flixo-pro/ ) to estimate the psi value of the frame plus the glass conductance to enable a combined R-value to be estimated.

I still have no idea how an analyst looking at a curtain wall or highly glazed non-residential building is supposed to complete the  required analyses with these data. There is no accompanying VT or SHGC data, just this table of R-values. I should note that I believe these latter data are also necessary in residential performance calculations as well!

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