I'm working on a baseline model to meet the LEED certification ASHRAE Standard 90.1 in OpenStudio 1.11 .

In order to set up the U-Factor to exterior fenestration to meet the 90.1-2007 Region 1A, I would need to reach 6.81 W/m².K.

In the first submission to USGBC, I had used a component from OpenStudio Office Library: “ASHRAE 90.1-2007 ExtWindow Metal ClimateZone 1”, that uses Simple Glazing System Window Materials. However, the U-Factor result in the report Envelope Summary: Exterior Fenestration, after considering the film, was 5.827 W/m².K, different from the said 6.81 W/m².K.

In the review, the USGBC asked me to correct the U-Factor to the values in the Standard .

So, I tryed to use a component from BCL: “90.1-2007 Nonres 1A Window Metal framing all other”, that uses another method to model the glass. In this case, the Glass U-Factor in Envelope Summary is 6.42 W/m².K, not meeting the requirements again.

I was beggining to correct this manually, but as explained in this question, it is impossible to get this U-Factor only by modeling the glass, because of the convection thermal resistance from the films. I imagine that I need to model the Frames manually to do as requested, but I’m not sure if this is the real problem and how I could fix it.

For the Proposed Model, I have similar problems, but with U-Factor 7.1 W/m².K from Table A8.2 from ASHRAE 90.1 - 2007.

How can I model windows to meet these requirements and demonstrate this in the reports to the USGBC? Which is the best current way that have been used to model this in EnergyPlus?