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"Time not Comfortable" calculation method

asked 2015-07-30 13:50:51 -0600

Mazen_094's avatar

updated 2015-11-11 13:01:18 -0600

Hi, In my experiments on EP, I have run a simulation for an office to analyse the results. I do not expect the results to comply with ASHRAE 55-2004 standard. I just want to check how the program calculates different parameters.

The last section of the performance summary shows that I have 3226.67 Not Comfortable hours. However, the sum of each of the following output variables:

*Output:Variable,*,Zone Thermal Comfort ASHRAE 55 Simple Model Summer Clothes Not Comfortable Time,hourly; !- Zone Sum [hr]

Output:Variable,*,Zone Thermal Comfort ASHRAE 55 Simple Model Winter Clothes Not Comfortable Time,hourly; !- Zone Sum [hr] 

Output:Variable,*,Zone Thermal Comfort ASHRAE 55 Simple Model Summer or Winter Clothes Not Comfortable Time,hourly; !- Zone Sum [hr]

neither gives this number. Any ideas how I will go about this issue?

Best, ///// Here you can find the modelled office file and the output file. The output file contains the "Time not Comfortable" output variable taken at hourly steps throughout one year. You may wish to have a look as a reference.

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answered 2015-07-31 06:59:38 -0600

updated 2015-08-03 06:43:29 -0600

The "Time Not Comfortable Based on Simple ASHRAE 55-2004" from the "Comfort and Setpoint Not Met Summary" table in the "Annual Building Utility Performance Summary" report is based on the same values as what appears in the output variable:

Output:Variable,*,Zone Thermal Comfort ASHRAE 55 Simple Model Summer or Winter Clothes Not Comfortable Time,detailed; !- Zone Sum [hr]

But the value from the table is based on a sum of the times that one or more zones is not comfortable. The report is about the whole building and it would not make sense to simply add up the hours for each zone since that could (conceivably) result in more than 8760 hours per year uncomfortable, especially if the building had a large number of zones. Since the goal of that table was to show how many hours per year were unmet hours for ASHRAE 90.1 Appendix G, it seemed consistent to show the "not comfortable" hours using the same approach.

To replicate the values, you should be able to use the output variable shown above using "Detailed" timesteps and then using a spreadsheet, add up the times that at least one zone is shown as not comfortable.

Please also keep in mind that the time that is not comfortable is accumulated only for timesteps that the zone is occupied. In this case, "occupied" means having a the number of occupants times the occupancy schedule being greater than zero for a particular timestep.

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My simulated office is made up of only one zone. I know that the standard imposes the (OR) relation the unmet hours calculation and so I used a single zone to avoid surprises. I have exported the mentioned Output variable into a spreadsheet that contains: Timesteps, MRT temperature, Ta temperature, this variable, and some other similar variables. The complete details can be found from here. For each time step there seems a complete compliance with the operative temp & humidity curves of the 55-2004 standard. But the summation does not give the expected result.

Mazen_094's avatar Mazen_094  ( 2015-08-01 08:20:50 -0600 )edit

I looked at your spreadsheet file and the results are hourly, which is too coarse. As Jason said, you need to report at the detailed or timestep level, like this, Output:Variable,*,Zone Thermal Comfort ASHRAE 55 Simple Model Winter Clothes Not Comfortable Time,detailed; !- Zone Sum [hr]

note the "detailed" not "hourly" in the last input field.

Also the algorithm inside E+ does not place a minimum limit on humidity.

Archmage's avatar Archmage  ( 2015-08-02 15:01:54 -0600 )edit

I ran the simulation again and checked that it gives a "detailed" output so that results are shown every 10 minutes. The program also scales the "Time not Comfortable" parameter with 1/6 to account for smaller time steps. However, the final sum gives the exact result I obtained in the previous simulation. The new output file can be found from here. And is called out2.

Mazen_094's avatar Mazen_094  ( 2015-08-03 06:59:08 -0600 )edit

Remember to also report the count of people and filter out those times when there is nobody present to be uncomfortable.

Archmage's avatar Archmage  ( 2015-08-03 09:11:02 -0600 )edit

@Archmage@JasonGlazer There seems a bug somewhere! I ran the simulation using Open Studio and Energy Plus for the out.idf file available in the following path: <osm_folder>\Built_stp7\run\3-UserScript-0 The Output Results available from the HTML file in the following path: <osm_folder>\Built_stp7\run\5-EnergyPlus-0\eplustbl.htm are different from those available from the HTML file that can be obtained by launching a separate EP simulation using EP Launch application. Where the results in both are different and those obtained from EP comply with the results from the spreadhsheet.Files're: Here

Mazen_094's avatar Mazen_094  ( 2015-08-09 13:43:28 -0600 )edit

answered 2015-07-30 15:48:39 -0600

Archmage's avatar

updated 2015-07-30 16:29:05 -0600

That whole-building report is looking across all the zones in the building, so to match it you would have to compare those outputs looking at all the zones.

Fanger PMV values are a bit more useful, in my opinion. But, of course, many feel it is all about Unmet Hours.

If you want to reduce the ASHRAE 55 hours, you will want to tighten up the thermostat range which will help drag the surface temperatures into the acceptable range.

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I would give Fanger's method a go when I sort out where the difference comes from for the default method. But like I said earlier to a colleague in the same thread: "The multi-zone calculation method may result in some surprises and so I ran my simulation with a single zone". The thermostat range is left default with +-0.2 tolerance and everything is left to default settings. You may want to have a look at the output results from here.

Mazen_094's avatar Mazen_094  ( 2015-08-01 08:27:20 -0600 )edit

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Asked: 2015-07-30 13:50:51 -0600

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Last updated: Aug 03 '15