Volume 38, Issue 5, May 2003
The Standards Maker
Shouldn't We Understand the Old Ones First?
by Dez Farnady
In some dark attic office, probably somewhere in the Midwest, there is a little man with horn-rimmed glasses, a receding hairline and a fist full of pens in his pocket-protected shirt pocket, writing the scheme for all of the glass performance standards we are stuck with today. We have solar heat gain coefficients, solar energy transmittance, metric K values, ultraviolet ratings, U-values for summer daytime and winter nighttime, light-to-solar-gain ratio, sound transmission loss and sound transmission class ratings, shading coefficients and visible daylight and interior and exterior reflectance requirements. The facts and numbers just seem to pour out of his quill pen as if he knew what the hell he was doing.
And here we are, out here in the light of day trying to figure out just what it is that those numbers really mean. While we are trying to make heads or tails out of those ratings and numbers, the glass makers keep sending him more money, encouraging him to continue coming up with more esoteric obscurities to further confuse us.
Small wonder that I still get embarrassed calls in the middle of the night from old time glass guys. These are guys who will not admit to anybody else that they donít understand any of this stuff. They donít know how to figure out an R-value because they have looked at every manufacturerís documentation and are having a tough time getting passed the ultraviolet value and the U-factor. They use me as their primary source because they think that I may know the answers, understand their questions and Iíll never tell on them for asking. Hey, Iím still not telling. Iím not naming names.
There has to be another way. Far be it from me to wish to put the hungry little man out of business, but it would be nice to eject him from his ivory tower. We need to retrain him to use language that does not require me to be a translator. We donít seem to be going that way. He seems to be heading for greater rather than lesser obscurity. He is sending more ratings and a new alphabet soup of meaningless mumbo jumbo into architectural specifications and building department requirements.
Letís Try This
I have a proposal. Obviously, no one is going to pay attention to it, but I get to propose it anyway. What if we just went back to the basics and waited until everyone understood them before we went on to all of the rest?
We started with daylight transmission. If there is a hole in the wall, all the light coming through it is 100 percent. Any less than that is measured as a portion of the light coming through a window or skylight. If clear glass blocks 10 percent of the visible light, then the light transmission of clear glass is 90 percent of the light transmission of the hole in the wall. Now, that was not too tough. So why canít we do something like that with heat coming in or sound coming in or heat going out?
Shading coefficient works sort of like that, but it uses a lite of window glass as a comparison base. If the base heat gain through a piece of eighth-inch window glass is 1.0 then a shading coefficient of .50 represents half as much heat. That is still pretty logical, but as we get into measuring heat loss it starts to get sticky. Measuring the insulating value of a conductor like glass starts to get complicated, and by the time you get to measuring sound transmission and STC and STL ratings, confusion reigns supreme. Now watch this Ö I will probably get letters from all types of engineers explaining it all.
Thanks for the help, but I am not the one who needs the explanation. The explanation needs to go to the standards maker. He needs to understand that incomprehensible standards are no better than no standards at all. Simple comparison ratings and standardized calculations are the only hope. Donít give us more ways to measure more things. Just make sure we understand how you measure the bread-and-butter basics.
Dez Farnady serves as general manager of Royalite Manufacturing Inc., a skylight manufacturer in San Carlos, Calif. His column appears monthly.
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