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Problem with OpenStudio results

asked 2016-11-09 06:45:24 -0500

poppo92's avatar

updated 2017-05-04 09:09:53 -0500

Hi everyone, I have a serious problem to understand how I got these results. I want to show you 2 cases of the same building, just with different construction sets, and the final results that are not reliable in my opinion. Case1 is composed by construction set made by me, and Case2 has the default construction set " OfficeCZ1 189.1 2009" in OpenStudio.

CASE 1 (the better one) : U-value Ext.Walls 0,14 W/m2K , U-value Roof : 0,08 W/m2K , Window conductivity: 0,9 W/mK (triple glass low emissivity downloaded from BCL)

CASE 2 (Construction Set Office CZ1 189.1 2009) : U-value Ext.Walls 0,96 W/m2K , U-value Roof : 0, 28 W/m2K , Window conductivity: 2,10 W/mk (theoretical glass)

It seems that the case1 has better thermal parameters than the 2nd case. Anyway these are the temperature and RH results for one room of the building (but result are quite the same for every room), called by me Room1

CASE1 : Mean Temp 111 (F) and RH 33%

CASE 2 Mean Temp 71 (F) and RH 63%

How is this possible? Why Case1, that is more isolated than Case2, has in the end a higher mean temperature? Is it possible that this result is caused mostly by the windows? I want to post here also the comparison of temperature during the year shown with ResultsViewer. Has anyone any suggestion about why I got these results? Furthermore, looking at the temperature tab, I see that in Case1 are analysed only 836 hours, and in Case2 are analysed 8760 hours. Why in the 1st case only 836 hours are taken into account?

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Hi, which is the windows SHGC in every case?

HJOJOA's avatar HJOJOA  ( 2016-11-09 07:54:56 -0500 )edit

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answered 2016-11-09 10:29:51 -0500

Based on these temperatures I assume that you don't have any HVAC system.

Understanding the results is a matter of thinking about all of the heat gains and heat losses, not just the envelope. If you insulate a room with high internal loads, the insulation keeps the heat in. There are many question/answer pairs on this site that explain how to dig into this topic. I'd start by adding the Zone Report from BCL to your model and checking that out.

The 836 hrs is a bug that I noticed yesterday in the humidity table. The >= 88F box has an artificial cutoff on the high end. Since your mean temperatures is 111F, most of the hours should show up in this box. What you are seeing in ResultsViewer is accurate.

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Just an FYI, the 836 hrs bug was filed and fixed (for both the humidity and temperature tables). It will show up in the next major release of OpenStudio.

aparker's avatar aparker  ( 2016-11-09 15:34:18 -0500 )edit

Infact I didn't set any HVAC because this building has not hvac, it works only with thermal mass and natural ventilation. Unfortunately the "zone report" does not give any output. Is this because I don't have hvac system?

poppo92's avatar poppo92  ( 2016-11-10 04:54:04 -0500 )edit

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Asked: 2016-11-09 06:45:24 -0500

Seen: 289 times

Last updated: Nov 09 '16