Relative importance of individual EnergyPlus Fields

Hi guys,

New Rhino/Grasshopper/Ladybug/Honeybee/OpenStudio/EnergyPlus user here. Any help/advice the experts around here could provide would be greatly appreciated. :slightly_smiling_face::+1:

For some context, I am working on a project looking at the effect of climate change and building design in a factory with the following steps/goals:

  1. Rather than use TMY files, we will monitor the outside environment for at least 12 months
  2. Simultaneously monitor the inside environment for at least 12 months
  3. In the mean time build a model of the factory in Rhino, Grasshopper (LB + HB[Eplus])
  4. Use the outdoor/indoor measurements to validate the accuracy of the model
  5. Apply climate change weather models to see the conditions workers will face in the future and what methods (besides air conditioning) can be applied to cool the factory when humidity/temperatures rise (e.g. white roof, green roof).

I am trying to better understand the underlying assumptions of EnergyPlus and EPW files.

Specifically to what extent does missing data in certain variables in EPW files influence the EnergyPlus outputs.

We have a weather station of our own, indoor weather stations/sensors for inside the factory and access to 3h data from a local meteorological agency for some variables we cannot collect ourselves.

I have provided a table is below to help better understand the variables we have and those we donโ€™t.

Essentially my question is:

  • If we cannot measure Horizontal Infrared Radiation Intensity and Opaque Sky Cover at all and allocate the EPW file as missing data will this significantly influence the model of the building? As in the thermal environment of the workers (temperature and relative humidity).

  • Further if we do the same for Total Sky cover where data is missing (as we can get this data but only at 3h intervals) will this significantly influence our model?

I have run two example TMY EPW files I put through a basic GH+HB model. One had missing data for these variables, one had the original TMY data values. My output for hourly zone indoor temperature and humidity over the year did not differ, but I wasnโ€™t sure if this is correct or not?

Variable Variables used in E+ from EPW file Our Weather Station (outdoors) Our Sensors (indoors) Local City Weather Station
Dry Bulb Temperature {C} X X X
Dew Point Temperature {C} X X X
Relative Humidity {%} X X X
Atmospheric Pressure {Pa} X X X*
Horizontal Infrared Radiation Intensity from Sky {Wh/m2} X
Direct Normal Radiation {Wh/m2} X X
Diffuse Horizontal Radiation {Wh/m2} X X
Wind Direction {deg} X X X
Wind Speed {m/s} X X X
Total Sky Cover {.1} X X*
Opaque Sky Cover {.1} X
Liquid Precipitation Depth {mm} X X*
* = DATA SAMPLE RATE IN 3h (not the 1h preferred)

@chris Hey Chris any possible insight into this?

The best place you can ask these questions would be the unmethours groups (which i think you already did).
I donโ€™t believe there will be an absolute answer for your question. The influence of weather data can affect according to location, project type and between building proposals.
Some of the data you listed will affect mainly daylight simulations rather than energy ones (sky related).

I suggest to look also at the E+ Engineering reference to see how calculations are done (from them see the variables involved).

The interior monitoring will help for calibrating and validate your model.