Sunlight from our windows on a day are pretty much predicable.Why are we interested?
Because we can tell when and where we have this:
also this, glare that we want to get rid of.
You can use design to give occupants this amenity by looking at the solar access.Tasks in this tab help you familiarize with variables needed for the tracking of sunlight,and how your design can benefit from it.Do the tasks on a sunny day would be easier and more interesting :)
Tracking the sun starts with identifying two solar angles: solar altitude and solar azimuth.
Altutide describes how high the sun is, and azimuth tells the orientation where the sun is located,
but where sunlight can reach inside ROOM also depends on which orientation the window faces.Now, find out the latitude of your city, the current local time, and where you get sunlight inside your own room,
input the latitude and local time into ROOM, modify the dimensions of ROOM and the window to which of your own room, and move the slider of orientation to locate the white patch in ROOM in a position as close to where you get sunlight in your own room, and now you can tell to which orientation your window faces.
One of the apparent changes when going from one place to another in the world is sunlight.In this task you will observe this change between London, Singapore and Melbourne.
Let's begin with London (latitude = 51.5 degrees North) in the Northern Hemisphere.
Keep/input the dimensions of ROOM and the window the same as your own room, and make the window face due south (orientation = 0 degree).Now check the white sun patch in ROOM and the two solar angles at the following times:morning(9:00), noon(12:00), and afternoon(15:00) on summer and winter solstices and equinox.You can take screenshots of ROOM at those times by pressing the 'Screenshot ROOM' button below.This shall give you a good overview of sunlight access of your room over the year in the specified location (London).You may note down the number of hours when sunlight access is available on those days and how deep the white sun patch reaches on the floor.
Moving to Singapore (latitude = 1.4 degrees North), close to Equatorial.
Repeat the analysis and see how the sunlight access is different from which in London,
and then to Melbourne (latitude = 37.8 degrees South) in the Southern Hemisphere.
After reviewing the sunlight access in the three places over the globe,try to summarize how sunlight access changes over the day in different times of the year, as latitude varies.
Having understood how to predict sunlight availability in a specific geographical location,we can now start looking at manipulating sunlight access in a room through design.Pick a location (can be that of the project you are working on) and input its latitude,
and input the following room and window dimensions as the base case design
The window is relatively small, with a window-to-wall ratio equal to 10%.
Review the sunlight access in the room over the day and over the year in the same way as you did in the previous task.Again, taking screenshots can help you see the variations and note how deep the sun patch reaches on the floor.
Now let's see how the sunlight access changes as we enlarge and move up/down the window, following the steps:
Next, change the depth of room (measured from the facade with window) as follows:
We have covered by far the main design parameters you can play with to manipulate the sunlight access in a room.Changing sunlight access by design often also influences the indoor daylight distribution.You can check how one is associated with another using both this tab and the daylight factor tab.
If you have completed the first 3 tasks in both this and the daylight factor tab, we have a design task for you now.
The visual environment of a daylit spcace is more vivid and natural,
in comparison with a space lit by artificial lighting, which also consumes electric energy.
Daylight Factor is used for estimation of the light level (over the working plane) in a daylit space.
Daylight factor varies at different spots in a room, and the average value provides a good overview for an early stage design.Tasks in this tab reviews how the average daylight factor over the working plane changes with different design parameters,and how it is influenced by the external obstruction.
Window is the most common element where daylight enters the building.This task covers the main parameters of a window that influence the amount of daylight penetrating through it.Light from a sunny sky (mainly direct) and an overcast sky (mainly diffused) penetrates window differently.The method introduced here is applicable for the overcast sky, where less light is available,and it relies more on the design to lit the room with daylight.
Input the following room and window dimensions as the base case design, and note down the associated daylight factor (use screenshot to save the result),
then observe and note down the changed daylight factor as you enlarge the window, following the steps:
Due to reflection and absorption, the light a window allows to penetrate drops as more glazing layers present.
With the enlarged window (5m2), change the light transmittance as follows and see how daylight factor varies
Daylight transmitted through the window reaches the internal surfaces (ceiling, floor, wall, window),and only a proportion of that is reflected back to the indoor space and lit the working plane.The amount of light being reflected depends on the light reflectance of the surface,
and some typical values for different colours paint and materials are listed below:
Ceiling usually has a bright finish and the common range of reflectance is 0.7-0.8, we will assume 0.7 for the task.
A wider range of floor finishes can be found in buildings and we will select 0.5 (birch) for the task.
Light to and from the walls is more likely blocked by internal obstructions (e.g. furniture),and thus light reflection with the walls should consider the obstructions to more closely represent real internal environment.Assuming the obstructions have an average reflectance of 0.5 and the percentage of wall area they block lies between 30% - 70%,
the average wall reflectance with various finishes (with obstructions) can have the following values, and we will pick the highlighted range for the task
Input the following room and window dimensions as the base case design, and note down the daylight factor with different wall reflectance,
then increase the room height and the floor area as follows and observe how daylight factor varies with wall reflectance in the two cases.
Daylight from the sky is partially blocked by obstructions outside the window.
The larger proportion of sky view from the window being blocked, the less light can enter the room.
The level of obstruction can be quantified by an obstruction angle.
Surrounding obstruction is therefore a major factor influencing the available daylight.
Adjust the obstruction as specified, input the following room dimensions, and observe the difference in daylight factor between the smaller and bigger window.
Make sure you reset the reflectance of all internal surfaces to the following values (wall: 0.5 ceiling: 0.7 floor: 0.5) after task 3.
Increase the height of the obstruction, and observe how daylight factor varies with the smaller and bigger window.
Next, reduce the distance to the obstruction, and observe how daylight factor varies with the smaller and bigger window.
