<div dir="ltr"><div>Hi,</div>
<div>Chapter 31 (Fenestration) of Ashrae handbook fundamentals has average overall U-values for different frame types (weighted average for a frane of 2.5" I believe, which also includes the glassedge effect). Accurate U-values need to be calculated using NFRC standards, using approved software (in the US this is LBNL Windows and Therm). </div>
<div> </div>
<div>I am not aware of a visible light transmittance requirement, but the lower the transmittance, the less daylighting benefits you will get, as you know, so there are no energy benefits for having a low Vt. Glass manufacturers work hard to keep light transmittances high and SHGC low.</div>
<div> </div>
<div>Hope this helps</div>
<div>Kind regards,</div>
<div>Karen</div>
<div>(Arup Facades)<br><br></div>
<div class="gmail_quote">On Mon, Sep 22, 2008 at 12:06 PM, Josh Greenfield <span dir="ltr"><<a href="mailto:JGreenfield@primerachicago.com">JGreenfield@primerachicago.com</a>></span> wrote:<br>
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<p>Does anyone have any rules of thumb on a quick/easy approximation for taking a Center-of-Glass U-value and converting it to an Assembly U-value based on industry standard assembly constructions? I know this depends on a lot of variables, like frame material and conductance, and the size of the overall glass assembly, etc., but I'm just looking for a quick estimate on performance reduction for comparisons to other window types for a particular building.</p>
<p> </p>
<p>Also, is there an ASHRAE 90.1-2004 Baseline glass Visible Light Transmittance (VLT)?</p>
<p> </p>
<p><span style="FONT-SIZE: 10pt">Josh Greenfield, <span style="FONT-SIZE: 7.5pt">PE</span></span><span style="FONT-SIZE: 7.5pt">, LEED AP</span><span style="FONT-SIZE: 10pt"><br>Senior Associate<br>Primera Engineers, Ltd.<br>
100 S. Wacker Drive, Suite 700<br>Chicago, IL 60606<br>312.606.0910 Main<br>312.242.6392 Direct<br>312.606.0415 Fax<br></span><span style="FONT-SIZE: 10pt"><a title="blocked::mailto:jgreenfield@primerachicago.com"><span style="COLOR: blue">jgreenfield@primerachicago.com</span></a><br>
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<br></blockquote></div><br><br clear="all"><br>-- <br>Karen Elisabeth Mozes<br></div>