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Does E+ consider interior shading when calculating the operative temperature?

asked 2018-07-16 08:50:56 -0600

rafael.alonso gravatar image

updated 2018-07-16 10:54:53 -0600

Hi all,

I´m working on the thermal analysis of a wintergarden, made of polycarbonate with an internal shading that deploys depending on the temperature.

Is the operative temperature calculated with the temperature of the shading material, or with the temperature of the polycarbonate roof? I don´t see many changes between both options, and I guess it should make a difference.



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answered 2018-07-26 18:03:36 -0600

This may get a little deep, but I want to document the details here.

  1. Based on a quick inspection of the source code, it appears that the surface inside face temperature (TempSurfIn) for a window is the temperature of the inside face of the glazing. This variable is used for meant radiant temperature and operative temperature calculations (wrong for a shaded window).

  2. A separate effective surface temperature is calculated for shaded windows (EffInsSurfTemp) which is defined as "Effective inside surface temperature for window with interior blind or shade; combination of shade/blind and glass temperatures." This temperature is used for interior radiant exchange (correct).

  3. For the equivalent layer window model (Construction:WindowEquivalentLayer) EffInsSurfTemp = TempSurfIn, so you may see the impact you expect if you use the equivalent layer window model.

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Many thanks for the detailed reply - I´m picking up on this now that I have a case to test and workaround it.

  1. Great to know, so I will discard Operative Temperature provided by E+, and calculate it separately using the air temperature and surface temperatures from point 2.

  2. Is there any output to pull out the "Effective inside surface temperature for window with interior blind or shade; combination of shade/blind and glass temperatures" Going through the list of outputs, there is nothing that resembles it.

  3. Wouldn´t this mean that the shading is fixed, always deployed?

rafael.alonso gravatar image rafael.alonso  ( 2018-10-31 07:17:23 -0600 )edit

re 2. No. It would not be difficult to add if you want to build your own custom version.

re 3. Well, yes, but you could use EMS Surface Construction State to change the window construction as desired.

MJWitte gravatar image MJWitte  ( 2018-10-31 15:10:22 -0600 )edit

Ah, great thanks! I'll explore option 3 through the EMS Surface Constructtion State.

rafael.alonso gravatar image rafael.alonso  ( 2018-11-01 04:53:37 -0600 )edit

I finally got the EMS Surface Construction State working, really handy. However, it seems that none of the shading objects,

WindowMaterial:Shade:EquivalentLayer WindowMaterial:Drape:EquivalentLayer WindowMaterial:Blind:EquivalentLayer WindowMaterial:Screen:EquivalentLayer

has any field to specify thickness and material conductivity. How could I model something like a 5mm thick curtain, so that it adds to the thermal resistance of the whole window?

rafael.alonso gravatar image rafael.alonso  ( 2018-11-07 12:00:21 -0600 )edit

WindowMaterial:Gap:EquivalentLayer is the only part of the equivalent layer model with user inputs for thermal characteristics. The thermal performance of the other layers are calculated internally. So, you could add another layer of gap+glazing to represent the drape thermal resistance.

MJWitte gravatar image MJWitte  ( 2018-11-07 19:21:14 -0600 )edit

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Asked: 2018-07-16 08:50:56 -0600

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Last updated: Jul 26 '18