Fabrication of green material for the wall and considering the humidity caused by vegetation perspiration to calculate the UTCI outdoor thermal comfort index

Hello friends
I have some problems, thank you for your help me.:pray:

  1. I want to obtain the effect of evaporation and perspiration of green walls and vegetation and water to calculate outdoor thermal comfort UTCI.
    Is there a solution to this problem in honeybee and ladybug?
    Can this effect be considered with Dragonfly?
  2. I want to produce various green materials in Haneybee, such as Low vegetation and grass. How do I do that?
    In the model “providedhttp://hydrashare.github.io/hydra/viewer?owner=chriswmackey&fork=hydra_2&id=Green_Roof_In_Energy_Model&slide=0&scale=1&offset=0,0”
    by dear @chris , I do not know where the information in this panel came from?
    image

Hi @farnoosh,

Here you can find more information on what is exactly calculated.

image

1 Like

@Erikbeeren , thank you for your help🙂

@farnoosh

FYI the Dragonfly-UWG component, (used to model UHI) models the impact of vegetative transpiration from green roofs, trees and grass (although in a crude way).

The UWG subtracts a fraction of sensible heat gain from the net radiation absorbed by vegetation to represent the latent impact of vegetation. These are represented by the grass and tree latent fraction inputs in the GH component.

The model thus assumes that plant stomata is closed after sunset, so transpiration is a function of net radiation, and furthermore the latent heat to net radiation flux is constant (there are studies that back this up). However, the impact of different tree/grass ratios are not incorporated into the UWG air moisture balance, so the transpiration impact is limited to just the surface heat balance of vegetated roofs, and the grass/tree cover on the ground.

2 Likes

@farnoosh @SaeranVasanthakumar ,

I once created a outdoor surface temperature animation using honeybee_legacy. For the input epw I used the UrbanWeatherGenerator from dragonfly. For the grass spots I used the definition above. For the pavement I used concrete as material. For the soil/pavement I used “create EP ground”

The result was this animation:

ezgif.com-gif-maker(1)

The effect of the of the different materials was clearly visible.

2 Likes

First of all, thank you for @SaeranVasanthakumar’s good explanation.
@Erikbeeren , I wanted to ask exactly the same question.
Is it possible to attribute the material to the zones through the Honeybee, then add vegetation and trees through the Dragonfly, and finally include “environment temperature” in the UTCi index through the ladybug?
Is it possible?

@farnoosh,
Yes you can add this material to Honeybee constructions.

For this simulation I made a new EPW file using UWG from Dragonfly.
This EPW I used for the input in Honeybee. The whole simulation I did in honeybee.
The pavement I modeled as “EPground” zones.
Buildings I modeled as zones.
Trees I modeled as context (it takes only into account the shading caused by these trees which is probably a bit to optimistic).
For the UTCi workflow I am afraid I can’t help you.

1 Like

@Erikbeeren
Thank you very much for your good guidance.
I do this and review the results.

@farnoosh You can find all examples I used on hydra.
http://hydrashare.github.io/hydra/viewer?owner=chriswmackey&fork=hydra_2&id=Trees_in_Outdoor_Thermal_Comfort&slide=0&scale=1&offset=0,0
http://hydrashare.github.io/hydra/viewer?owner=chriswmackey&fork=hydra_2&id=Green_Roof_In_Energy_Model&slide=0&scale=1&offset=0,0

I would add that the UWG component in Dragonfly is a good candidate for modeling your microclimate only if it is developed with many buildings. It’s only meant to be used where the rural context of the EPW from airport weather stations won’t capture the urban heat island effect in more developed areas.

For scenario’s where you want to model in high resolution the impact of vegetation on outdoor microclimate, I believe ENVI-met is considered state of the art, although I personally have never worked with it.

1 Like