How to Capture the Effect of Fan & Heat Capacity in UTCI Study

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Hi All,

I’m currently working on an UTCI simulation using Ladybug tool: Dry Bulb Temperature (DBT) + Mean Radiant Temperature (MRT) + Wind Speed + Relative Humidity (RH). So, I’ve 2 questions over here:

  1. How should I capture the heat capacity of the ground materials while simulating for MRT? Thermal mass material eg concrete conducts heat better than timber.
  2. How should I take the ceiling fan effect into account for UTCI as higher wind speed would improve the results? I’m considering using Eddy but not sure how should I insert the wind speed output from Eddy into each grid cell for UTCI.

Regards,
Austin

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Hi @Austin - Welcome to the forum. I’m not the best person to answer this question but to give you a starting point.

If I remember correctly, @chris’s recommendation is to model the ground as a Honeybee room with the desired construction on the roof.

This should be possible. I know that this has been requested before, and at least in the Honeybee recipe there is an input for wind speed matrix.

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To flesh out Mostapha’s answer a little more, you should be using the HB UTCI Comfort Map component to run the study since this will use EnergyPlus to compute surface temperatures of anything modeled as a Room in the input Honeybee Model. You can use the HB Ground component to easily format a Honeybee Room into something that will accurately model the ground temperatures in the comfort maps and you use the _soil_constr_ input to describe the heat capacity and reflectivity of the ground material.

The question about celling fans has thrown me off a little. UTCI is an outdoor comfort model that should only be used to evaluate comfort on the outdoors (and, ideally, only for cases where people are walking since UTCI uses a hard-coded assumption that the human subject has a metabolic rate of walking). Are you saying that you have ceiling fans on the outdoors? If so, you can plug in some custom values for _wind_speed_, though this is getting a little hairy because this input is supposed to be the meteorological wind speed at 10 meters. So you might have to adjust it a little.

If this is wrong and you’re actually running an indoor comfort study, I would recommend using an indoor comfort model like Adaptive Comfort or PMV Comfort.