# Air flow volume output from HB Read results

**URL:** <https://discourse.ladybug.tools/t/air-flow-volume-output-from-hb-read-results/19735>\
**Category:** honeybee\
**Tags:** energyplus, honeybee, thermal-comfort, airflow\
**Created:** [October 12, 2022, 10:47pm UTC](https://discourse.ladybug.tools/t/air-flow-volume-output-from-hb-read-results/19735 "2022-10-12T22:47:34Z")\
**Posts on this page:** 10\
**Page:** 1

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**Author:** ![deepthi.ravi](https://discourse.ladybug.tools/user_avatar/discourse.ladybug.tools/deepthi.ravi/32/34863_2.png) [@deepthi.ravi](https://discourse.ladybug.tools/u/deepthi.ravi)\
**Post date:** [October 12, 2022, 10:47pm UTC](https://discourse.ladybug.tools/t/air-flow-volume-output-from-hb-read-results/19735/1 "2022-10-12T22:47:34Z")

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![Screenshot 2022-10-12 233624](https://discourse.ladybug.tools/uploads/default/original/3X/2/7/27295dcf71a701e1b6ad0a1d96414bf398406a2e.jpeg)

I’m trying to derive Air flow volume output from the Honeybee 1.5 version of HB Read results, which was available as an output option in the earlier versions. However, I’m unable to obtain the results. I’m unsure whether there is something I’ve missed out in the script. Please do have a look at it and help me out  
@chris @mostapha  
[THERMAL SIMULATION.gh](https://discourse.ladybug.tools/uploads/short-url/iJWcyLuanU9UYJtMOIOwy9X3OKp.gh) (175.9 KB)

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**Author:** ![AbrahamYezioro](https://discourse.ladybug.tools/user_avatar/discourse.ladybug.tools/abrahamyezioro/32/3_2.png) [@AbrahamYezioro](https://discourse.ladybug.tools/u/AbrahamYezioro)\
**Post date:** [October 13, 2022, 4:14am UTC](https://discourse.ladybug.tools/t/air-flow-volume-output-from-hb-read-results/19735/2 "2022-10-13T04:14:30Z")

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You need to ask for the `surface_energy_flow_ output` in the `HB_SimulationOutput` component.  
-A.

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**Author:** ![deepthi.ravi](https://discourse.ladybug.tools/user_avatar/discourse.ladybug.tools/deepthi.ravi/32/34863_2.png) [@deepthi.ravi](https://discourse.ladybug.tools/u/deepthi.ravi)\
**Post date:** [October 13, 2022, 9:39am UTC](https://discourse.ladybug.tools/t/air-flow-volume-output-from-hb-read-results/19735/3 "2022-10-13T09:39:46Z")

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![Screenshot 2022-10-13 103841](https://discourse.ladybug.tools/uploads/default/original/3X/8/9/89a55b8f7714eb2ab62af03ff2898b0420227619.jpeg)  
I have asked for it already.  
Yet, unable to receive the required values of airflow

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**Author:** ![deepthi.ravi](https://discourse.ladybug.tools/user_avatar/discourse.ladybug.tools/deepthi.ravi/32/34863_2.png) [@deepthi.ravi](https://discourse.ladybug.tools/u/deepthi.ravi)\
**Post date:** [October 13, 2022, 9:43am UTC](https://discourse.ladybug.tools/t/air-flow-volume-output-from-hb-read-results/19735/4 "2022-10-13T09:43:40Z")

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![Screenshot 2022-10-13 104141](https://discourse.ladybug.tools/uploads/default/original/3X/9/5/95135129e04a8fcf32eec5537e31000f107ee08a.jpeg)  
Additionally, I also realized that there is no result going out of my natural ventilation component. Does that have any relevance as to why I’m unable to receive airflow values?  
If yes, how do I resolve this?

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**Author:** ![AbrahamYezioro](https://discourse.ladybug.tools/user_avatar/discourse.ladybug.tools/abrahamyezioro/32/3_2.png) [@AbrahamYezioro](https://discourse.ladybug.tools/u/AbrahamYezioro)\
**Post date:** [October 13, 2022, 1:10pm UTC](https://discourse.ladybug.tools/t/air-flow-volume-output-from-hb-read-results/19735/5 "2022-10-13T13:10:59Z")

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Now i see that you are asking for an output of a Legacy component. It is not anymore in LBT.  
I’m not aware of this output at all.  
-A.

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**Author:** ![deepthi.ravi](https://discourse.ladybug.tools/user_avatar/discourse.ladybug.tools/deepthi.ravi/32/34863_2.png) [@deepthi.ravi](https://discourse.ladybug.tools/u/deepthi.ravi)\
**Post date:** [October 13, 2022, 2:00pm UTC](https://discourse.ladybug.tools/t/air-flow-volume-output-from-hb-read-results/19735/6 "2022-10-13T14:00:07Z")

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If anyone else has any idea as to why I’m unable to arrive at the results, please let me know. It’s urgent. Thank you.

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**Author:** ![ElzineBraasch](https://discourse.ladybug.tools/user_avatar/discourse.ladybug.tools/elzinebraasch/32/17_2.png) [@ElzineBraasch](https://discourse.ladybug.tools/u/ElzineBraasch)\
**Post date:** [October 14, 2022, 2:44am UTC](https://discourse.ladybug.tools/t/air-flow-volume-output-from-hb-read-results/19735/7 "2022-10-14T02:44:16Z")

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Hi Ravi,

Several things here - first off, you need to apply a proper schedule to set your cooling setpoints, rather than entering in a list of 24 values to the cooling setpoint input. I made a schedule and added the Apply Schedules component to the workflow - you’ll see in looking at the air temps that it will then work during the day

 ![image](https://discourse.ladybug.tools/uploads/default/original/3X/4/e/4ef5e8ee70e3f09f894f47701f0a643cd6f8a7f5.png)  
 ![image](https://discourse.ladybug.tools/uploads/default/original/3X/8/e/8ec6a243e9cc084788f2222fb6271b27f2f19f60.png)

Then, in regards to opening the window, I would suggest you open the window with a setpoint lower than your cooling one, so say 24C and cooling kicking in at 25 or higher, so that you’re not cooling outside air that you’re bringing in. You’ll want to set the max setting for the window control to be just before the cooling would kick in (I haven’t changed this from what you had).

Sadly though I can’t find the output for air flow either and is a good question to ask incase you want to know how much air flow can be expected from the window. You can look at the nat\_vent output, but that gives you kWh…

Sorry I can’t be of much more help than that.

[THERMAL SIMULATION.gh](https://discourse.ladybug.tools/uploads/short-url/23UsiDLGfFL5FaibzC4F7TvApFE.gh) (202.8 KB)

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**Author:** ![SaeranVasanthakumar](https://discourse.ladybug.tools/user_avatar/discourse.ladybug.tools/saeranvasanthakumar/32/5079_2.png) [@SaeranVasanthakumar](https://discourse.ladybug.tools/u/SaeranVasanthakumar)\
**Post date:** [October 15, 2022, 5:10am UTC](https://discourse.ladybug.tools/t/air-flow-volume-output-from-hb-read-results/19735/8 "2022-10-15T05:10:33Z")

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@deepthi.ravi, @ElzineBraasch

You can usually find most outputs by searching the EP Input/Output reference, and using the HB components for searching and reading custom EP results. From the wind and stack  
ventilation [section](https://bigladdersoftware.com/epx/docs/22-2/input-output-reference/group-airflow.html#outputs-1-002), you can get the ventilation flow rate with the following output terms:

- Zone Ventilation Current Density Volume Flow Rate
- Zone Ventilation Standard Density Volume Flow Rate
- Zone Ventilation Air Change Rate

You’ll want the “Current Density” flow rate, if you want the flow rate that’s effecting the zone heat balance, more detail on this here:

> [@Zone Infiltration absolute value-variable results](https://discourse.ladybug.tools/t/zone-infiltration-absolute-value-variable-results/18380/7):
>
> @lillytoul I figured out the cause of the variation, or at least the main contribution. EnergyPlus is using an outdoor air density calculation when converting the infiltration into a mass flow rate which is derived from site air pressure and temperature. So the fluctuation reflects changes in the site outdoor temperture and air pressure. There doesn’t seem to be any mention of this at all in the EP documentation, but this [Unmet Hours post](https://unmethours.com/question/16841/how-is-site-standard-air-density-calculated-in-energyplus/)[1] breaks down the formula they’re using - essentially a…

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<div class="post-metadata">

**Author:** ![deepthi.ravi](https://discourse.ladybug.tools/user_avatar/discourse.ladybug.tools/deepthi.ravi/32/34863_2.png) [@deepthi.ravi](https://discourse.ladybug.tools/u/deepthi.ravi)\
**Post date:** [October 18, 2022, 10:32am UTC](https://discourse.ladybug.tools/t/air-flow-volume-output-from-hb-read-results/19735/9 "2022-10-18T10:32:12Z")

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![Screenshot 2022-10-18 112818](https://discourse.ladybug.tools/uploads/default/original/3X/d/3/d3a6601a3eb089f7ee03789d4cba6779ea028277.jpeg)  
I tried that, yet, the results say ‘null’ for both Zone Ventilation Current Density Volume Flow Rate and Zone Ventilation Air Change Rate.  
I’m not sure why. Could you please have a look at the script if I have done something particularly wrong?

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<div class="post-metadata">

**Author:** ![SaeranVasanthakumar](https://discourse.ladybug.tools/user_avatar/discourse.ladybug.tools/saeranvasanthakumar/32/5079_2.png) [@SaeranVasanthakumar](https://discourse.ladybug.tools/u/SaeranVasanthakumar)\
**Post date:** [October 18, 2022, 8:12pm UTC](https://discourse.ladybug.tools/t/air-flow-volume-output-from-hb-read-results/19735/10 "2022-10-18T20:12:00Z")

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Yeap, you need to add a custom simulation output component that tells the simulator to collect those report variable names. Or else it won;t show up in the custom results.

 ![image](https://discourse.ladybug.tools/uploads/default/original/3X/4/b/4b7e24c8174cebeec3b934009c542f066ab0730b.png)

Then your results work.