Modelling of Ventilated Facades with Cavity Blinds - Blind Parameters

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hamnmegs at's picture
Joined: 2011-10-02
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Hi Graham,

FYI, the new version of IDA ICE, which is currently in beta testing, has a
complete implementation of the ISO 15099 multi pane window model. This makes
it possible to model window and blind combinations from first principles as
you desire.

Best regards,

Per Sahlin

Per Sahlin's picture
Joined: 2011-10-02
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You can, within IES Virtual Environment, explicitly model blinds as you have described below:

First either divide the vented fa?ade into two zones (inner and outer air spaces) with a corrugated surface or add such a partition to one zone; every other facet of this corrugated surface will be a blind slat with specified material properties and tilt angle, etc., and the facets in between will be holes. Having completed this, if you made two zones to begin with, then combine them as one zone with the blinds as floating partition or planar surface elements. If you need to model the fa?ade over the course of a year with the louvers at dynamically varied angles or in various states of deployment, I?d suggest multiple runs with post-processing to combine the data into a single year. For this you would combine selected results based upon incident solar gain for that hour, or whatever variable you choose to determine the control of the louver angles, etc.

It is important that you end up with a single combined zone between the inner and outer glazing to ensure proper calculation of transmitted direct and diffuse solar gain (however, you will still require separate vertically stacked zones for each story, etc. of the building fa?ade as means of determining differences in buoyancy with MacroFlo). The thermal properties of the blind materials and their surfaces will also be important to determining the absorbed solar gain, re-radiation to the fa?ade elements, and convective heat transfer to the air in the vented cavity. Lastly, because the theory applied in MacroFlo is based on the flow characteristics of openings that are small in relation to the spaces they connect?i.e., it?s set up to account for the flow resistance (aero drag coefficient) of operable windows, other punched openings, etc.?you will need to have a look at Section 7: Techniques for Modeling Flow in Fa?ades and Flues in the MacroFlo Calculation Methods section of the user manual. This will tell you how to adjust the dimensions of your fa?ade cavity model so that a MacroFlo opening at each floor height (or similar) will appropriately account for resistance from openings, mullion protrusions, catwalks, surface friction, and so forth.


Timothy Moore

Timothy Moore's picture
Joined: 2011-10-01
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