Hi everyone

 

For a case-study I compared the results (electrical lighting, heating and cooling energy) for a single zone model oriented to the west with "no shading" and with "conceptual shading" (see attachment).

I am a little astonished to find out, that the simulation predicts a higher heating demand for the model without shading (where are the solar gains in winter?) and a higher cooling demand for the model with shading.

I would also expect the cooling energy to be quite high with no shading at all. But the cooling energy stays low even when I change the glass type and the g-value from 41% to 72%.

 

Are there some mistakes I could have made?

 

Any hints are welcome.

 

Thanks,

 

Caroline

 

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Hi Caroline,

I think that the results make sense. When you employ the shading device the lighting levels decrease and the lighting demand as I see in the graph increases significantly. So that's why the cooling energy increases (because of the heat generated by the lighting equipment). In the same way the heating demand decreases because the heat from the lights help to maintain the desired temperature.

I hope that this helps.

Kind Regard,

Kostas

Dear Kostas

Thank you for your response and your time to look at my question.

I can understand your explanation and with a g-value of 41% it could more or less work. But what makes really no sense to me, is that I have a low cooling demand of 4.5 kWh/m2a with a g-value of 72% and no shading.

According to my experience this would normally result in high room temperatures, far beyound the cooling setpoint of 26°C (which would imply that the cooling must be switched on). 

Kind regards

Caroline


Kostas Mourkos said:

Hi Caroline,

I think that the results make sense. When you employ the shading device the lighting levels decrease and the lighting demand as I see in the graph increases significantly. So that's why the cooling energy increases (because of the heat generated by the lighting equipment). In the same way the heating demand decreases because the heat from the lights help to maintain the desired temperature.

I hope that this helps.

Kind Regard,

Kostas

Probably the amount of solar radiaton is very small and in this case the type of glass doesn't affect the results. Change the orientation of the building ( so that the window faces due south) and see what happens.

Kind Regards,

Kostas

Dear Kostas (and others)

I tried that already. For the south orientation the results are almost the same. But I used the same model. Consequently, if the problem is connected to the model I copied the mistake.

Are there other ideas around?

Kind regards

Caroline

Hi Caroline,

Could you share your model, the climate file, and the names (and definitions if needed) of the materials you are using?

Best,

Alstan

Hi everyone

Attached to this mail you will find my model, the climate file and the material file. 

I hope this ist all the information needed. 

Thank you for having a look at it!

Best,

Caroline

Attachments:

Hi Caroline,

A few questions before I can look into your issue:

1. Did you make any custom EnergyPlus materials? If so, please attach the idf materials file too.

2. Could you upload the EPW version of your DRY file?

3. What materials are you switching between for the glazing in the thermal simulations?

Thank you,

Alstan

Hi Alstan

Please find attached the documents you where asking for.

I switched from 

a) Glazing_triple_Pane_Yuanda to

b) Glazing_DoublePane_Clear_80

Thank you for taking the time to look at my model

Best,

Caroline

Attachments:

Hi Caroline,

This isn't conclusive, but probably gives you a direction to investigate in. First, overall the climate is rather cold. The histogram below shows this, where ODB = outdoor dry bulb values from your DRY file. Second, your shoebox has six exposed thermal surfaces. That means there is a lot of places where heat can escape that is less realistic in a larger building. You might consider moving your wall, ceiling and floor surfaces to the 'adiabatic' layer such that they don't work as free thermal syncs for you.

I also didn't try out your shading setup, but there is a possibility if the shading is down often, that can strongly mitigate solar gains as well.

All the best,

Alstan

Dear Alstan

I assume, you couldn't find somethin wrong in the model.

I will test the shoebox principle with another simulation programm (ESP-r). If there are still unexplainable differences I might come back to you.

Thank you for your time and the hints you gave me.

All the best,

Caroline

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