[Bldg-sim] Glass center-of-glass to assembly U-Value?

[karen mozes]

Hi,
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).

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.

Hope this helps
Kind regards,
Karen
(Arup Facades)

On Mon, Sep 22, 2008 at 12:06 PM, Josh Greenfield <
JGreenfield at primerachicago.com> wrote:

>  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.
>
>
>
> Also, is there an ASHRAE 90.1-2004 Baseline glass Visible Light
> Transmittance (VLT)?
>
>
>
> Josh Greenfield, PE, LEED AP
> Senior Associate
> Primera Engineers, Ltd.
> 100 S. Wacker Drive, Suite 700
> Chicago, IL 60606
> 312.606.0910 Main
> 312.242.6392 Direct
> 312.606.0415 Fax
> jgreenfield at primerachicago.com
> http://www.primerachicago.com
>
> Be Green...please consider the environment before printing this email.
>
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-- 
Karen Elisabeth Mozes
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