RE: [EnergyPlus_Support] thermal and optical properties calculation of facade systems

Emanuele,

WINDOW 6.2 and THERM 6.2 actually can model shading devices of the three general types:

- Venetian blinds

- Frits

- Woven shades

Your system is closest to woven shades type, as the woven shades are modeled as a grid of vertical and horizontal weaves. While it is true that woven shades algorithm for diffuse part is developed for denser weave than you have, it is also true that diffuse portion is very small and will not significantly affect your results.

I would encourage you to try to model your system with WINDOW 6.2/THERM 6.2, because results will be much more accurate than any approximation and rule of thumb that you may use otherwise.

D. Charlie Curcija
DesignBuilder Software
16 Bridge St.
Millers Falls, MA 01349

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From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Emanuele Naboni
Sent: Thursday, February 11, 2010 8:08 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] thermal and optical properties calculation of facade systems

Hello Edward,

Yes, the grid is on the outside, the open area factor could varies from 44% to 66% as a function of the final product installed.

Surely the grid has an impact as a wind shelter so that the wind coefficient will be effected (I hope to find the way to use a reliable coefficient without CFD calculations).

Playing with WIS I have now that is possible to model this case too.

Thanks for the advices,

Emanuele

On Thu, Feb 11, 2010 at 1:40 PM, Edward G. Lyon <eglyon@xxxxxxx> wrote:

Sounds like your grid is on the outside and casts a shadow on the window. A fair approximation is to calculate the glazing alone using Window. Adjust the exterior wind coefficient if you think the grid creates some shelter for the window. The grid is just a net free area that limits the % of sun light that reaches the glass. Most of your light transmittance properties are simply the % of calculated values. Things can be more complex if the grid is almost opaque, and you may need to use CFD for air movement and calculate grid/glass reflections separately.

Having the grid inboard of the glass is also more complicated because of reflections and absorption that are not as simple as just shading the glass from the outside.

Ned Lyon, P.E. (MA)
Staff Consultant

SIMPSON GUMPERTZ & HEGER
781.907.9000 main
781.907.9350 direct
781.907.9009 fax
www.sgh.com

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Emanuele Naboni
Sent: Thursday, February 11, 2010 5:04 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] thermal and optical properties calculation of facade systems

Dear All,

Does any of you have an idea on what software tools could be used to calculate thermal and optical transmission properties (e.g., thermal transmittance, total solar energy transmittance) of a complex window system based on the ISO 15099:2003 method?

The system that I am trying to study is composed by a double pane glass protected by a vertical metal grid which is 750mm (2' 6") detached from the window.

From my understanding neither Window 6.2 nor WIS are able to model this system to describe thermal transmittance, total solar energy transmittance, visible transmittance, etc..

Is there any suggestion? Thank you so much for any possible help.

Regards,

Emanuele

--
Emanuele Naboni - www.e3lab.org - info@xxxxxxxxx
MArch, PhD Building Science, LEED AP, EU licensed architect
sustainable design consultant - consulente per la sostenibilita' di tecnologie, edifici e citta'

per l'Italia: 346.4133337
from US: +39.346.4133337
skype: emanuelenaboni

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