Indoor CO2 levels using Strings

Hey @chris @TheodorosGalanos,

After thoroughly going through other discussions, I’ve been led to this individual string I found which had the idea from Theodoros Original String.

Yes, !- Carbon Dioxide Concentration
Carbon_dioxideSchedule, !- Outdoor Carbon Dioxide Schedule Name
No, !- Generic Contaminant Concentration
Carbon_dioxideSchedule; !- Outdoor Generic Contaminant Schedule Name

Carbon_dioxideSchedule, !- Name
ANY NUMBER, !- Schedule Type Limits Name
Through: 12/31, !- Field 1
For: AllDays, !- Field 2
Until: 24:00, !- Field 3
400; !- Field 4

*, !- Key Value
Zone Air CO2 Concentration , !- Variable Name
Hourly; !- Reporting Frequency

I’ve been trying to understand this string, where Field 4, does it take into account, the default outdoor CO2 levels?

I would appreciate some assistance with this if someone has any ideas and/or has a revised string?.

Additionally, I would also be glad to hear if there’s a more straightforward way to obtain the CO2 levels in Ladybug.


Hi @Adarsh ,

You may just want to wait for us to implement CO2 sensors within Honeybee schema as we have an open issue for this that is on our development roadmap:

I don’t know exactly what happens when you specify a Zone CO2 setpoint (400 PPM) that is exactly the same as the outdoor CO2 schedule but my initial guess is that you’re effectively telling your ventilation system to run all of the time. So it’s as if you don’t really have a CO2 sensing system at all. Also, it may be worth noting that 400 PPM is below the current atmospheric CO2 level (~420 PPM).

This section of the EnergyPlus Input/Output Reference would likely also likely shed some light on how this E+ object wroks:

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Hello @Adarsh,

In the EnergyPlus Schedule:Compact you’ve mentioned, Field 4 represents the value that the schedule will hold at all defined times. In this case, it’s set to 400 ppm, which is a common baseline for outdoor CO2 levels. This value does not dynamically account for actual outdoor CO2 levels, which can vary based on location and environmental factors. It’s often used as a static reference point for indoor CO2 simulations.

For a more accurate simulation that takes into account varying outdoor CO2 levels, you would need to measure or estimate the outdoor CO2 concentration and update the schedule accordingly. This could involve using a sensor or referencing local environmental data. Some sources suggest that typical outdoor CO2 levels can range from 300 to 400 ppm, but may be higher in urban areas due to factors like traffic and industrial activity.

If you’re looking for a more straightforward way to obtain CO2 levels in Ladybug Tools, you might consider exploring the Honeybee EnergyPlus component that allows for additional strings. These strings can be used to add objects to your model that simulate CO2 sources and sinks. You can also check out the Ladybug Tools forum for discussions on indoor CO2 level measurement using Honeybee4.

Remember, it’s important to ensure that the CO2 levels used in your simulation reflect the conditions you’re trying to model as closely as possible for accurate results.

I hope this helps, and happy coding with Ladybug Tools!

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