Outdoor comfort under canopy

I am trying to simulate comfort condition in a public plaza in between two buildings. The plaza is covered by a big canopy made of transluscent panel (a.k.a. kalwall). I am running both CFD and EnergyPlus simulations to calculate the comfort condititon in the plaza. I think I got the CFD part covered, but I still have questions on how to treat the plaza. I presume that the plaza needs to be a thermal zone in EnergyPlus.

  1. Any thoughts on how to model the transluscent panel for the canopy? My thought is to get a glass property close enough to the kalwall, and then set the “transluscent” field to yes.

  2. How to model the entrances to the plaza? In reality, the entrances are open, but for EnergyPlus this has to be closed. Any thoughts on how to model this?

@erydjunaedy
I am not very clear about your question. Could you upload some image about the question or Rhino& Grasshopper file?

Here is the image, and an example file.

street_canyon_with_canopy_v2.gh (578.6 KB)

I don’t know what are you looking for. But, if I was you I would treat it as an outdoors and I would put the canopy as a Context in HB with a translucent material. Would that work for you?

Pardon me for not knowing the lingo. I am new to Ladybug and the other insects. But what is a context? Do you mean as shading device? I do not think that will work, as I need the inside surface temperature of the canopy. Shading device cannot have that output.

HB context its a component of Honeybee that can be plugged into your simulations. It does work like a shading, yes. If you are looking for surface temperatures you could do a microclimate mapping simulating it as an outdoor, what its closer to reality than an indoors with air walls by the entrances. I would recommend you this workflow from hydra.
http://hydrashare.github.io/hydra/viewer?owner=chriswmackey&fork=hydra_2&id=Outdoor_Microclimate_Map&slide=0&scale=1&offset=0,0

In a simple explanation that workflow treats the space as an outdoors but considering the heat from the surroundings and your canopy. If you analyse it as an indoors you will rely on indoor calculations for the ventilation, and depending on the distance between the entrances that you have that may not be reliable, that is the main reason why I would do the microclimate mapping.

Hi Julia,

In the example you mentioned, everything that has surface temperatures is modeled as EPlus zone. All the “context” is modeled in EPlus as shading device. The problem with shading device is that we cannot extract the surface temperature.

So if I model the canopy as a shading device, then I can only model the shading effect of the canopy. What I want is more than that. I want to see if the canopy is actually heating up the occupant underneath. And for that I need the surface temperature of the canopy. That is why I model the street canyon as a thermal zone.

I will ignore the ventilation effect. I will make sure that the indoor air temperature is the same as the outdoor air temperature, by supplying enough ventilation air from outside.

The actual wind speed will be calculated by using CFD.

With don’t you model the canopy as a “plenum zone” of 5cm width? If you do that you will have access to the surface temperatures of the canopy. In the case of doing that you would have to process the properties of your canopy material to make it work as with 2 layers though.
If it helps you I used the plenum zone as a surface heater on a public terrace to analyse the impact of their surface temperature on the people using it to basically understand how many, how big and how frequent we should have them. The results were looking quite reliable.

The problem that I see is that the temperature under the canopy should not be the same as outdoors, but if you like it better that way it is perfectly fine.

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There was an interesting paper about this presented in IBPSA by Tarek Rakha to calculate surface temperatures without running an energy model. I assume @chris can clarify the best practices for cases like this. Still not sure if it’s possible to assign the temperatures to a surface without running an energy model and based on a more straight forward calculation (like the one in the paper).

Hi Mostapha, can you send me the link to the paper please? Thanks.

Hi Julia, I do not think the plenum zone will work in this case. I am trying to model a canopy, i.e. there should be a solar radiation (direct and diffuse) that goes through the canopy. I am not sure that EPlus is capable of transmitting solar radiation through a zone. Even if the amount of radiation exiting a zone is calculated, I do not think the radiation can be used to “shine” on the plaze underneath the canopy.

A Framework for Outdoor Mean Radiant Temperature Simulation: Towards Spatially Resolved Thermal Comfort Mapping in Urban Spaces
http://www.ibpsa.org/proceedings/BS2017/BS2017_677.pdf

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@erydjunaedy did you find a solution?
I’m working on Ladybug Tool 1.2.0. My model is this:
image
I am following two paths:

  1. consider the shading by setting the adiabatic condition for the wall surfaces and assigning the EP construction to the roof and the exposed floor. To take into account the transparent overhang I added a sub-face to the roof.


    I have these surface temperatures

  2. consider the shading as HB shade and as you said the surface temperature of the overhang is not given; I have these surface temperatures (ground and wall)

It would be useful to receive feedback on the method to be used.
Thanks.