What % UV is blocked or absorbed by Pella Architect Series Low E
double pane windows?

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Request for Question Clarification by silviares-ga on 21 Jul 2006 14:38 PDT

Hello bob9216-ga

I did a little research and the window you are talking about is feaured here 
http://www.pella.com/products/windows_patiodoors/Detail.asp?path=/products/windows/doublehung/architect

here they claim that the "Low E" glass meets  ENERGY STAR requirements.

If you click the ENERGY STAR link and then click on the US map (I
believe you are in the US) you will find what the requirements are for
the different areas.

The standards are expressed in 

U Factor 
which measures how well a product prevents heat from escaping. The
rate of heat loss is indicated in terms of the U-factor of a window
assembly. U-factor ratings generally fall between 0.20 and 1.20.
In the United States, the U-factor is usually expressed in Btu/h ft²
F. The metric equivalent unit is W/m² K.

SHGC 
is the fraction of incident solar radiation admitted through a window,
both admitted through a window, both directly transmitted, and
absorbed and subsequently released inward. SHGC is expressed as a
number between 0 and 1. The lower a window's solar heat gain
coefficient, the less solar heat it transmits.  see
http://www.efficientwindows.org/shgc.cfm

Now there is no direct correlation between SHGC and UV blocking so I
cannot deduct the percentage of UV blocking from that.

However Ultraviolet (UV) resistance is often promoted by window
manufacturers because of its role in fading colors of furnishings.
Some low-e coatings boast UV transmission under 1 percent. However,
about 20 percent of sunlight's fading power comes from visible light.
So even completely blocking UV doesn't stop fading altogether. If you
want to know more you can check http://oikos.com/esb/35/glazing.html

I realize that this is not answering your specific question but I am
wandering if this is enough information for you to be satisfied with
the answer. If it is I can post this as an answer.
I have also already contacted Pella asking for the UV percentage
blockage of the window and will let you know if they come back with an
answer

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Request for Question Clarification by silviares-ga on 24 Jul 2006 11:13 PDT

Hello bob9216-ga
did you get a chance to see my request for clarification? 
Still no answer from Pella but I will keep you informed.

silviares