# Most efficient way to 'flow' this humidity change

**URL:** <https://community.homey.app/t/most-efficient-way-to-flow-this-humidity-change/59041>\
**Category:** Flows\
**Created:** [January 24, 2022, 6:18pm UTC](https://community.homey.app/t/most-efficient-way-to-flow-this-humidity-change/59041 "2022-01-24T18:18:59Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Caros](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/caros/32/12410_2.png) [@Caros](https://community.homey.app/u/Caros)\
**Post date:** [January 24, 2022, 6:18pm UTC](https://community.homey.app/t/most-efficient-way-to-flow-this-humidity-change/59041/1 "2022-01-24T18:18:59Z")

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The Idea:  
IF: humidity changes  
AND: humidity changed by more then 5% in the last 30 seconds  
THEN: turn on ventilation at max

Why this flow? If I check humidity above a certain level, for example 75%, then I am to late. Then possibly the shower is running already a long time. I want to achieve two things:

- Turn on the ventilation as soon as possible if the shower is on
- Try to use as less resources for this flow as possible.

I can come up with many different solutions, like having variables every 30 seconds and check the difference between them every 5 seconds. But I think this gives a lot of resources for these actions. Are there more clever ways to turn this into a flow?

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**Author:** ![Peter\_Kawa](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/peter_kawa/32/173848_2.png) [@Peter\_Kawa](https://community.homey.app/u/Peter_Kawa)\
**Post date:** [January 24, 2022, 8:32pm UTC](https://community.homey.app/t/most-efficient-way-to-flow-this-humidity-change/59041/2 "2022-01-24T20:32:51Z")

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Something like this  
First create a numeric variable; I called it ‘LastHumidityValue’. Enter 50 as value.

Needs some finetuning, but you get the idea

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**Author:** ![Ronald\_de\_Boer](https://sea1.discourse-cdn.com/flex025/user_avatar/community.homey.app/ronald_de_boer/32/13873_2.png) [@Ronald\_de\_Boer](https://community.homey.app/u/Ronald_de_Boer)\
**Post date:** [January 27, 2022, 4:20pm UTC](https://community.homey.app/t/most-efficient-way-to-flow-this-humidity-change/59041/3 "2022-01-27T16:20:32Z")

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Hi,

I solved this in a quite similar way.  
This flows compares the “old” and the “new” value of humidity.  
When the difference is more than 6%, my ventilation turns on.  
This is controlled in another flow.

[https://homey.app/f/dHOksW/](https://homey.app/f/dHOksW/)