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Glassed Zone Temperature

asked 2018-11-01 10:18:58 -0500

taher.ahel gravatar image

updated 2018-11-05 08:55:41 -0500

There is a simple fully closed glassed zone without any infiltration, ventilation or HVAC system. The floor is bare ground and there is no basement or slab. In this case the zone temperature should be around 60C in winter and 100C in summer. but it is around 20C in winter and 45C in summer. why?

It is modeled by EnergyPlus 9.0.1

This is the model: Glassed Zone File



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Are there any warnings/errors in the err file?

shorowit gravatar imageshorowit ( 2018-11-01 13:21:13 -0500 )edit

what is the U-value for your glass, and how much heat are you losing through the ground? A simple look at the zone loads report may tell you where the heat is going.

mdahlhausen gravatar imagemdahlhausen ( 2018-11-01 14:45:11 -0500 )edit

@shorowit No, there is no warning and error. Indeed I've used the ZoneCoupledKivaBasement E+ example file then made some changes. I put the energyplus file above.

taher.ahel gravatar imagetaher.ahel ( 2018-11-03 03:26:35 -0500 )edit

@mdahlhausen In literature my glass U-Value is calculated 6.4 but energy plus calculated it 3.4. I just have to fill it's spectral specification and it's thermal conductivity. I wasn't able to solve the problem for weeks and I've simplifed the model to ask here and I attached above.

taher.ahel gravatar imagetaher.ahel ( 2018-11-03 03:32:18 -0500 )edit

where did you get your values when you say "the zone temperature should be around 60C in winter and 100C in summer". And did you check heat loss through the ground and conduction through windows?

mdahlhausen gravatar imagemdahlhausen ( 2018-11-05 11:31:32 -0500 )edit

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answered 2018-11-06 17:24:46 -0500

Looks like you've found the issue - it's the ground boundary conditions. For a model like this, the result will be highly sensitive to the ground heat transfer. A ground construction is required, because the Kiva ground model must have some type of surface as a boundary condition to the zone. For this application, I would try a rather thick slab of soil, with the foundation settings such that the soil surface is completely in-grade.

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Thanks for response. I didn't get last sentence: " I would try a rather thick slab of soil, with the foundation settings such that the soil surface is completely in-grade." (English is not my native language)

It means I shouldn't use Kiva? and which E+ object would you suggest me to use in order to simulate aforementioned glassed zone temperature?

taher.ahel gravatar imagetaher.ahel ( 2018-11-07 08:55:06 -0500 )edit

Kiva should work OK here. In the Kiva:Foundation object, set both "Wall Height Above Grade" and "Wall Depth Below Slab" to zero so that the slab is modeled in-grade. Set "Footing Wall Construction Name" to a layer of soil, 0.3m thick or so..

MJWitte gravatar imageMJWitte ( 2018-11-07 19:35:32 -0500 )edit

I've done it but the results are the same.

Here is the model in E+ 9.0.1 : Model link

Here is the weather file (from E+ website): Weather File Link

taher.ahel gravatar imagetaher.ahel ( 2018-11-08 05:41:56 -0500 )edit

I've played around with this file, and even with an adiabatic floor, temps reach about 60C max. Time to review the material properties and the measured data including the weather data. A model like this with a very thin envelope will be extremely sensitive to small changes in the glazing material properties.

MJWitte gravatar imageMJWitte ( 2018-11-16 16:44:11 -0500 )edit

Thank you teacher...I will check every detail of material... Now it is very close to what I expect...

taher.ahel gravatar imagetaher.ahel ( 2018-11-17 06:30:52 -0500 )edit

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Asked: 2018-11-01 10:18:58 -0500

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Last updated: Nov 06 '18