Fine Tuning Low-E Glass

Mark Meshulam is an expert witness and consultant for windows, low-e glass and building exteriors.

I feel sorry for anyone charged for the responsibility for choosing or specifying Low-E glass. The choices are nothing short of overwhelming.

See for yourself:


Guardian Glass
PPG Glass-Residential
PPG Glass-Architectural
Viracon Glass


Although I have been “doing windows” since 1981, I am still staggered by the volume of information and array of choices available. What seems to be missing in these presentations, and what I hope to provide here, is a starting point and a framework for understanding. Here are some initial thoughts:

1. Different Low-E glass makeups are designed for particular climates, and even whether the building is residential or commercial.

2. Low-E Glass has evolved to a point of being so spectrally selective that if you were to tweak your system to the utmost, you would not only make selections based on climate and desired appearance, but you might select different glass by building exposure. This is where we could be in the future, but is not commonly practiced now.

3. U-Values and SHGC of .30 are governmentally encouraged this year through tax credits. Next year they could be mandated in building codes. See resources below.

4. Although the Federal Government is pushing for a universal standard of .30 for U-Value and SHGC, regional differences and specific applications might suggest selected deviations.

And so, in an attempt to de-mystify glass selection, I am putting forward the Chicago Window Expert’s Low-E Glass Design Guide. I invite any commentary you care to contribute. Remember, these are simply guidelines. As opinions come in, as new products are developed and as new codes are implemented, this simple chart is sure to evolve. But for now, her it is…

RESOURCES:
International Green Construction Code (IGCC) Now in the Works
U.S. Green Building Council (LEED)
Green Building Initiative (GBI)
ASHRAE – The American Society of Heating, Refrigerating and Air-Conditioning Engineers
Lawrence Berkeley National Laboratory

Confused about Low-E glass?