SOLAR ANALYSIS - Overshadowing & Site Analysis

Loading the Overshadowing Model

The first step in this tutorial is to load a model file containing some buildings. We are going to use the model shown above to look at overshadowing of the empty site shown in orange. This is to contain a child care centre, so our preliminary site analysis is going to look at the best location for the morning play area. As morning recess is from 10:00-10:45am, it is desirable its location has access to direct sunlight during this period in the winter months.

1. Open  Overshadowing.eco  from the Tutorial Files directory located in your main ECOTECT Install directory.
   
   There are quite a few zones in this model, representing various buildings and site features.
2. Select the Shadows item from the Display menu.
   
   This displays shadows on the entire site and opens the Shadow Settings control tab to the right of the Drawing Canvas.
   
   
   
   Shadows are shown for 12:0pm on April the 1st in Perth, Western Australia as this was the last setting saves with the model.

Setting the Date and Time

1. In the Date/Time toolbar, change the time to 10:15 and the date to the 21st of June (mid-winter in the southern hemisphere).
   
   You can set the time and day using either the spin buttons or by clicking in either text box and using the PageUp/PageDown keys. You can moderate the increment value (1, 15 or 60mins) by holding down the Shift or Control key using both methods.
   
   
   
   The shadows should update each time a change is made, resulting in the following image.
   
   
   
   This give some indication of the area we need. We could cycle though a range of dates and time getting a slightly better idea of what is going on, or we could use a sun-path diagram to display an entire years overshadowing in one image.

Displaying a Sun-Path Diagram

The default format is a stereographic diagram. Refer to the main help file for a detailed description of each type of sun-path diagram and how to read them.

1. Click select the small point object within the orange site.
   
   This is displayed as small 'asterisk' as shown below. Make sure that is the only object selected.
   
   
2. Select the Sun-Path diagram... item from the Calculate menu.
   
   This will display a Sun-Path Diagram showing the sun-path and overshadowing of that point, which should be very similar to the image shown below.
   
   
   
   This indicates that from about May through August this point is in shade from just before 10:00am to just after 12:00pm. It is therefore not appropriate to put it in the middle of the site on the north side.
3. With the sun-path diagram still displayed, select the Transform button in the left toolbar and then the Move item from the displayed pull-right.
4. Select the Zoom Window button from the View toolbar and drag a zoom box around the orange site.
   
   You can achieve the same view using the Shift and Control keys whilst dragging with the Right Mouse button down. Basically you want to get a view similar to the one shown in Point 1 above.
5. Click in the Drawing Canvas and drag the selected point to the east side of the site.
   
   It does not matter where you first click as long a you then drag in the right direction and look at the selected point as you move. For example, you may want to click in an empty area of the screen, such as at Pt 1 shown below, and drag to the right to Pt 2. Note that the Cyan line indicates that the orthogonal snap is on and that you are dragging in the X axis only.
   
   
   
   When you click at Pt 2, the sun-path diagram will update.
   
   
   
   This is much better as it shows brief opening for sun penetration exactly at the times required - 10:00am to 11:00am. This is cutting it quite fine, however it may be the only area of the site that receives sun at those times. You may wish to check if that's the case by simply moving the selected point around to other areas of the site and examining the resulting overshadowing diagram.

Interacting with Shadows

When the sun-path diagram is displayed, you can use it to interact with displayed shadows in the model. To do this you may want to resize the dialog so that you can see both it and the model in the main application window, as shown below.

1. If you have turned shadows off to select the point, select the Shadows item from the Display menu in the main application window and keep the Sun-Path Diagram dialog displayed.
2. Click and drag the Left Mouse button in the sun-path diagram.
   
   This will cause the date and time to change, following the mouse. When you release the mouse button, the shadows in the Drawing Canvas will update to the new date and time. If you hold down the Control key as you drag, the shadows will update interactively.
   
   This direct link between the sun-path diagram and physical shadows can be very useful when you are trying to work out which buildings are actually causing the overshadowing at particular time, especially in a very complex environment. As a small additional exercise, you could continue your investigation in this area by opening the Zone Management dialog box and selecting different shadow colours for the different zones. This way you can more easily isolate the effects of each building.