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Is it reasonable to use Simple Glazing System Window Materials object to recreate a Double-pane glass windows?

asked 2015-07-16 15:40:27 -0500

hugoalmeida4's avatar

updated 2015-07-16 18:10:50 -0500

I have a cubic loft model with 4 windows (one per wall). Is it fairly reasonable to use the Simple Glazing System Window materials object to recreate a double-pane glass windows with this needed characteristics?

heat transfer coefficient Uw= 2.6 W/m2 K solar factor = 0.75

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answered 2015-07-16 16:45:28 -0500

It is reasonable if you build the window in a program like Windows 6 from LBNL and account for the frame construction in the U-value, SHGC, and VT. In other words, when using the simple glazing material make sure to use the assembly window values, NOT the center of glass window values.

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you're right, thanks.

hugoalmeida4's avatar hugoalmeida4  ( 2015-07-16 16:56:56 -0500 )edit

answered 2015-07-16 18:10:01 -0500

updated 2015-07-16 18:10:25 -0500

@TaylorRobert 's point is correct. The U-factor and SHGC must represent the entire fenestration system (both opaque and glazing portions of the window). In addition to using values from Window 6, you can use the NFRC ratings on actual fenestration products.

It is worth noting however, the simple glazing system takes a fairly simplistic approach in that it does not explicitly simulate multiple panes of glass (e.g., reflections between the panes), any special coatings on the interior or exterior of the window (e.g., low emissivity coatings), or any opaque components of the window (e.g., frames and dividers). All of these effects are lumped into a single, monolithic layer with the same U-factor and SHGC. The simple glazing system does do a fairly good job of simulating the angular dependence of solar heat gain.

This only guarantees similar performance at the NRFC rating conditions, though it is likely to be fairly representative under a wider range as well.

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Good point Neal. It is also worth mentioning that you can use the new frame and divider script which makes it easier to use "Glazing Window Materials". This process is detailed here Frame and Divider in OS but it is important to note that when using this process you need to actual draw each window in SketchUp, otherwise if you lump windows together (common modeling practice) you want have enough frame per window area and your windows will be too high performing.

TaylorRoberts's avatar TaylorRoberts  ( 2015-07-17 09:04:03 -0500 )edit

answered 2015-08-20 12:45:58 -0500

Chris Rush's avatar

Also, if you're doing more detailed daylighting simulations using Radiance, and the precision of the angular dependence is important, you may need to consider more complexity of the glass itself. Refer to this post:

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Asked: 2015-07-16 15:40:27 -0500

Seen: 14,475 times

Last updated: Jul 16 '15