In this tutorial you will learn how to prepare a Honeybee model room for a daylight simulation by assigning the material optical properties, creating a sensor grid and importing the relevant weather data. Daylight simulation can be performed in various ways in Grasshopper. There are five different daylight simulations explained in this tutorial:

•    Daylight factor simulation
•    Point-in-time simulation
•    Annual daylight simulation
•    Annual irradiance simulation
•    Direct sun hours simulation

Honeybee Daylight Simulation-v2 1/3

Designlink copied

This example refers to a shoebox geometry of an apartment which is on the ground floor of a 2-storeys building. It has a rectangular plan of 10m*10m and it has a height of 3m.

The apartment has an entrance from the road with an opaque wooden door and has also one operable window facing the street. The window is shaded with wooden horizontal louvres. On the left and right side there are adjacent apartments, but on the back side it is not neighbouring any other apartment or building.

The exterior walls are made of concrete in light grey colour. The slabs are also made of concrete and they are painted in white colour on the bottom side (ceiling). On the top part (floor), they are covered by timber in a darker colour. The interior walls are made of plywood and covered also in white paint.

Abbreviations:

HB(Honeybee), LB (Ladybug), DF (Daylight Factor), CIE (International Commission of Illumination), CBDM (Climate Based Daylight Modelling).

Exercise file

As a starting point for the Daylight Analysis in this tutorial you will need to have a HB room set-up ready. You can download or create the Grasshopper script and Rhino file from the “Honeybee model set-up” tutorial or use your own design. 

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Model preparationlink copied

Each time you want to perform a daylight simulation in grasshopper, there are some basic set-up parts needed. First the material optical properties need to be assigned to the HB model. Then a sensor grid needs to be created and the weather data need to be imported. 

Optical material properties

Before following on with the Daylight analysis, you should make sure that the relevant material optical properties are assigned to the faces of your HB model. In the steps that follow you will learn how you can assign optical material properties to the HB model. To do so, first the radiance modifiers per material are created, then the modifier subsets are created per face from which the modifier set is created. Lastly, the modifier set is assigned to the HB model after which you can visualize and check the modifiers. 

For a more accurate Daylight simulation, you should assign the values of the optical properties for each material in the corresponding surfaces. Specifically, you should specify the reflectance and transmittance.

•    Reflectance (for opaque materials), which is a percentage indicating the amount of light that is reflected by the surface when the light falls into it (the higher the reflectance, the more light is reflected).

•    Transmittance (for transparent materials), which is a percentage indicating the amount of light that is transmitted through the window (the higher transmittance, the more light passes through the window.)

Radiance modifiers per material

For each material of your project, a different Radiance modifier needs to be created, gathering its optical properties in it. In the HB-Radiance » Modifiers you can find the different material categories that you may use. For this tutorial we are only going to use the ‘basic’ modifier for Opaque and Glass materials, however for your specific project you might need other modifier types. 

Create glass modifier for each window material.

•    Create a glass modifier by

•    Define transmittance of window and input to _trans

Create opaque modifier for each opaque material.

•    Create an opaque modifier 

Table: Material properties example room

For more information on different material properties, a good database of materials and their reflectance values is available here

Modifier Subsets per face type

The second step for assigning the material optical properties to your HB model faces is creating the modifier subsets per face type. To assign the material properties to the corresponding HB faces:

•    Create modifier subset for each face type:
1.    

•    Connect the ‘modifier’ result of each Radiance material modifier to the corresponding face input of each Modifier subset. For this tutorial:

1.    Connect the ‘Dark timber/carpet’ modifier to ‘_exposed_floor_’ (HB Exterior Modifier Subset) and ‘_interior_floor_’ (HB Interior Modifier Subset).
2.    Connect the ‘Light Grey concrete’ modifier to ‘_exterior_wall_’ (HB Exterior Modifier Subset) and ‘_interior_shade_’ (HB Shade Modifier Subset).
3.    Connect the ‘Glass_Window’ modifier to ‘_window_’ and ‘_operable_’ (HB Subface Modifier Subset), so as to apply to both operable and non-operable windows.
4.    Connect the ‘Light timber’ modifier to ‘_exterior_door_’ (HB Subface Modifier Subset) and ‘_exterior_shade_’ (HB Shade Modifier Subset).
5.    Connect the ‘White paint’ modifier to ‘_interior_wall_’, ‘_ceiling_’ (HB Interior Modifier Subset) and ‘_exterior_roof_’ (HB Exterior Modifier Subset).

Assign the Modifier Subsets to the HB Room

The third step for assigning the material optical properties to the HB model is to create a modifier set from the modifier subsets and then input the modifier set to the HB room. The HB room and HB model creation should already be created – or copied – from tutorial “Set-up Honeybee room”. 

•    Create a modifier set by HB-Radiance » Modifiers » HB ModifierSet.
•    Connect the result of each Modifier Subset to the respective input of the Modifier Set
•    Give a characteristic name for the Modifier Set you are creating by Params » Input » Panel. In our example, you can write “Room1_Materials” in the panel.
•    Connect the ‘mod_set’ result of the HB ModifierSet component to the ‘_mod_set_’ input of the HB Room component.

Visualize & Check

Finally, you need to visualize the material optical properties of the faces to check if they are correctly assigned. In order to quickly check the attributes that are assigned to each face a HB label face component can be used that displays a label on each face in Rhino 

Sensor grid

As second step in the preparation of the HB model for a daylight simulation, a sensor grid has to be created for each room in the HB model. With the ‘HB Sensor Grid from Rooms’ component a grid is automatically created inside your room based on a given grid size and distance from the floor. The grid size refers to the size of sensor grid cells. The distance from floor refers to the vertical distance between the sensor grid points and the HB room floor. For this tutorial a grid size of 0.5 meters and a distance from the floor of 0.75 meters is used. Next, the created sensor grid should be assigned to the HB model with the ‘HB Assign Grid and Views’ component. 

•    Create a grid from rooms component by 

•    Connect the ‘model’ result from the HB model component to the ‘_rooms’ input.
•    Define grid size  and connect to the ‘_grid_size’ input 

•    Define distance from floor and connect to the ‘_dist_floor’ input 

Params
Input
Number Slider

•    Create a HB Assign Grids and Views component. 

•    Connect the ‘model’ result from the HB model component to the ‘_model’ input.
•    Connect the ‘grid’ result from the ‘HB Sensor Grid from Rooms’ component to the ‘grids_’ input.

Import the Weather data

Finally, it is important to import and load the weather data that correspond to the selected location to perform a daylight simulation. You can import and extract the respective EPW weather data by following the steps in the sections of the “Importing weather files in Ladybug” tutorial. The “Importing weather files in Ladybug” tutorial gives a detailed description on how to import and extract the EPW data for a specific location, specify a time period in a weather file. Additionally in the tutorial you learn to check the quality of the data by plotting the normal radiation graphs for the respective climatic data, as it is important to make sure that the EPW file we are using is of good quality and does not miss any data. In this tutorial the weather data will be extracted for the whole year.

A different type of weather object is needed depending on which daylight simulation you want to run. The Daylight Factor (DF) simulation does not need any weather input, the point in time simulation requires a specific sky condition (e.g. cloudy or sunny) based on the location and a weather data object is needed for the annual daylight, annual irradiance and direct sun hours simulations. To extract the location and wea object from a specific location, the epw file needs to be downloaded with a URL. From this the location can be extracted and the epw file can be converted into a wea object. 

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Daylight Factor simulationlink copied

The first way to perform a daylight simulation discussed in this tutorial is the Daylight Factor simulation. Here, you will learn what Daylight Factor is, how to create and run this simulation, how to visualize the results and what the guideline requirements are.

What is the Daylight Factor?

The Daylight Factor (DF) gives an indication of how a space performs in the ‘worst case scenario’ of overcast (i.e., very cloudy) sky conditions. Under such conditions, the DF is defined as the ratio between the indoor illuminance recorded at desk height inside a space and the outdoor horizontal illuminance under an unobstructed sky. It is therefore expressed as a percentage value.

The DF simulation uses a standard definition of such sky conditions, called the CIE Standard Overcast sky. This means that the simulation is invariant of the location of the building and the time period, so no weather data will be used as an input in this analysis.

The EN 17037 code for Daylight in Buildings gives requirements for the Daylight Factor. You can compare the acquired values with the acceptable Daylight Factor values related to the location of your project. If you are a TU Delft student, you can find it by logging in with your TU Delft account in the following page

Create & Run Simulation

To create and run the Daylight Factor simulation you have to create a HB Daylight factor component and input the ‘model’ result of HB Assign Grids and Views. You should pay attention to this, because it would create an error if you connected the ‘model’ result directly from the HB model component! Then you need to create a HB Radiance Parameter component to define the performance settings of the simulation. The recipe type of the radiance parameter should be set to 0, for running a DF simulation. 

For the detail level use 2 (high detail) in this tutorial. For further information on which detail level of radiance parameters you should choose or how you can select customized values for the radiance parameters, check the “HB customized radiance parameters” tutorial.

Lastly, a False Start Toggle is needed to start the simulation. Pay attention to selecting the HB FalseStart toggle when working with simulations. This toggle automatically turns back to False when closing the GH file, to prevent errors when opening the file. 

•    Create a HB Daylight Factor component.

•    Connect the ‘model’ result from the HB Assign Grids and Views component to the ‘_model’ input. 

•    Create a HB Radiance Parameter component. 

•    Set ‘_recipe_type’ of HB Radiance Parameter to 0 for a DF simulation with Params
Input
Number slider

•    Define ‘_detail_level_’ of analysis, use 2 (high level of detail) for this tutorial, with Params
Input
Number slider

•    Create a False Start Toggle component and connect it to the ‘_run’ input of the HB Daylight Factor component.

•    Double-click the False Start Toggle component in order to set it to ‘True’ and run the simulation.

Visualize the results

For easier comprehension of the simulation, you can visualize the results. A very convenient way to visualize the results obtained from any type of Radiance simulation is to create a Spatial Heatmap. A Spatial Heatmap is a 2-dimensional representation of the data per grid point obtained through the simulation. In each point, the corresponding value is represented by a colour.

To create a spatial heatmap for the DF results you can use the LB Spatial Heatmap component and connect the results for the simulation to the values input. The component uses the mesh from the created grid result of ‘HB Sensor Grid from Rooms’ to visualize the results on. Be aware that to visualize any results, you must already have run the simulation. You can use a LB Legend Parameters component to adjust the legend according to your simulation. By browsing your mouse over the different inputs of the LB Legend Parameters component, you can see which are the parameters that you can set each time. Define the graph title and used measurement units in a panel and connect those to the LB Legend Parameters component. 

•    Use a LB Spatial Heatmap component. 

•    Connect the ‘results’ from the HB Daylight Factor simulation component to the ‘_values’ input.

•    Connect the ‘mesh’ result from the HB Sensor Grid from Rooms component to the ‘_mesh’ input.

•    Adjust legend parameters with a LB Legend Parameters component. 

•    Define the graph title ‘Daylight Factor’ in a panel then connect it to the ‘global_title_’ input of the LB Spatial Heatmap component. 

•    Define the measurement units of the metrics to ‘%’ in a panel. Connect it to the ‘legend_title_’ input of the LB Spatial Heatmap component.

Params
Input
Panel