Internally "conditioned" Cavity Windows (not double skin facade)

We have a case to model where the office windows will have 1-2 inch cavity between 2 glass panels, and instead of a glass fill (like Argon or anything) we will have supply air pipes through the mullions. These pipes will basically act as "air curtains" where they will supply the cold air during the summers, and hot air during the winters.

I already have looked into the previous (as per my knowledge), and I wasn't able to find anything like this.

If anyone has any experience, comments, feedback etc, please feel free to share. I am not able to figure out how to model this either in Openstudio or EnergyPlus. Any feedback on "work around" will also be helpful.

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Harshul Singhal

asked 2017-09-26 17:04:51 -0500

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__AmirRoth__

updated 2017-09-27 19:20:52 -0500

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What is supplying the air through the mullions?

yungahhh (2017-09-26 17:36:52 -0500) edit

Mullions will act as diffusers.

Harshul Singhal (2017-09-26 17:50:57 -0500) edit

What's significantly different about this design than a double facade? It seems the same in principal.

Jim Dirkes (2017-09-26 18:59:42 -0500) edit

I'd suggest updating your initial question with more detail as you laid out in the unmet hours slack channel.

mdahlhausen (2017-09-28 15:51:22 -0500) edit

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It sounds like you are trying to accomplish something similar to return air integrated into lighting systems. In those systems, the conductive heat from the lights is captured by the return airstream, and does not enter the space. With your window system, you will be doing the same thing. The major difference is that by using the cavity between the two panes of glass, you are eliminating the insulating properties of this air gap. If you would otherwise use single pane glass, then you might see some energy benefits.

In regards to how to model it - you can use EnergyPlus's "airflow windows" to model airflow. See the example file AirflowWindowsAndBetweenGlassShades.idf

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kwalkerman

answered 2017-09-29 14:43:10 -0500

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Thanks @kwalkerman
Yes, I have used this airflow windows component by moving my energy model from OS to EnergyPlus. Much appreciated!

Harshul Singhal (2017-09-29 14:45:27 -0500) edit

EP 8.7 documentation http://bigladdersoftware.com/epx/docs... Also, as of OpenStudio 2.3.0, this object is not available in the API so would require an EnergyPlus measure to add to an OS model.

MatthewSteen (2017-09-29 14:52:30 -0500) edit

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Regardless of design question "why on Earth do you need to do this..?" the only thing you do is controlling the temperature of the air between the panes. What in return changes the U-value of the window. If the flow is enough to neglect the changes in air temperature: U'=Uglas(Tglas-Tin)/(Tout-Tin) This equation represents the energy balance from space point of view - we don't consider the amount of energy to support needed Tglas. Then, as I see, there is only one way to model variable U-value - to change surface convection coefficient by EMS actuator. Or to create a set of simple glazing systems with a range of possible U-values and apply their constructions by the same EMS actuator for construction stage. In any way you will have much more research tasks than real results.