Some of you may be familiar with a little program called Ecotect. It is a 3D building analysis program that assists architects in analyzing many aspects of a building’s performance, with a particular emphasis on creating energy efficient, sustainable designs.

An Introduction to Ecotect

Development of Ecotect commenced as part of Andrew Marsh’s Ph.D. thesis at the University of Western Australia. It has since grown to become a leading application for the analysis of building performance, offering a diverse suite of tools for assessing aspects of a design such as solar exposure, thermal performance, acoustics, lighting, shading, and much more.

Many of the early design decisions we make on a project will have a major impact on whether or not a building will use energy and materials efficiently. Consequently, the effect of these decisions needs to be quantitatively assessed during schematic design and design development. Ecotect is one such tool that assists architects to do this.

In this article, I hope to introduce to you some of the principles behind how Ecotect works, and how you can use it as part of the architectural design process, starting with schematic design.

Obtaining Ecotect

If you don’t already have access to a copy of Ecotect, you can download a trial version of the software 

Ecotect modeling principles

Figure 1 shows an example of an Ecotect model for a two storey residence. This model was created in Ecotect itself, but could have been modeled and exported from another application, such as SketchUp or ArchiCAD—Ecotect supports a wide variety of 3D CAD formats.

It is reasonably intuitive to view and navigate around an Ecotect model. Hold down the right mouse button, and you can rotate the view—the model always rotates about its centre, so you won’t get too dizzy as in some other CAD programs! Hold down the scroll wheel, and you can pan the model, and scrolling forward and backwards zooms in and out respectively.

Figure 1. A typical Ecotect model of a two storey residence.

The first thing you may notice about the model is that the walls and floors have no thickness (see Figure 2, which shows a closer view of one of the spaces). In Ecotect, the thickness of a wall or floor plane is a property of the material assigned to it (e.g., cavity brick, timber frame, reinforced concrete, etc.) and so it doesn’t need to be modeled in 3D. However, in the event that the walls and floors were modeled with thickness—such as if you imported a 3D model created in another application—Ecotect can compensate for the distance between these surfaces that should otherwise be adjacent. This will be explained in more detail in the following paragraph.

Figure 2. Walls and floors in an Ecotect model are represented as single planes, with the thickness being a property of the material assigned to that plane.

The model is broken up into a series of discrete spaces known as “Zones,” as shown in Figure 3. Zones serve a similar function to classes or layers in other CAD programs for organising elements of the model, except that in Ecotect, they also define areas for the purpose of thermal analysis. As a general rule, a zone must be created as a fully-enclosed volume—imagine that a zone is full of water and that it can be picked up and turned upside down. If any water can leak out, it is not a fully enclosed thermal zone. Therefore when you model one zone next to another, you model both of the wall planes that are adjacent, where each wall plane defines one enclosed volume. This overlap is compensated for when Ecotect performs an “Interzonal Adjacency” calculation.

Figure 3. Each space or volume in an Ecotect model is defined as a zone for the purposes of thermal analysis. Adjacent zones should still be modeled as fully enclosed volumes by themselves.

But what about doors and windows? Well, these elements don’t count when determining if a zone is fully enclosed, because of their relationship to the model. They are regarded as child objects that are inserted into parent objects such as walls, and so are still considered to form an enclosed volume (see Figure 4). A door or window can be assigned its own material properties (e.g., single-glazed aluminium frame, hollow core door panel, etc.). When you have a door or opening leading between one zone and another, there’s no need to “double-up” and model a door in each of the adjacent walls. Ecotect automatically accounts for the corresponding opening in the adjacent zone.

Figure 4. Elements such as doors and windows share a child-parent relationship with elements such as walls. Doors and openings leading from one zone to another don’t need to be created twice.

You can switch to different views of the model, such as orthographic or axonometric projections, via the View menu. To get a clearer view of your model in its entirety, try clicking on the Visualise page tab to the left of the main window. This shows the model in OpenGL (see Figure 5). You can use the Visualisation Settings control panel to adjust display options.Click back on the 3D Editor page tab and press F8 to return to the perspective view.

Figure 5. You can use the Visualise page tab to view your model in OpenGL.

Assessing Site Conditions

Even though this Ecotect model is relatively simple and unrefined, it can still be used to provide us with valuable information during the schematic design stage of a project. For example, we can use this model to consider site conditions and orientation, and evaluate if the proposed building envelope represents a suitable design response.

Firstly, let’s tell Ecotect where the project is geographically located, and the orientation of the site. Click on the Project page tab, which displays a summary of project information. Here, you can specify the location of the project by loading the Weather Data file. Figure 6 shows the location for this particular project specified as Perth, Western Australia (click the Reloadbutton to initialise the file), but there are many other data files included with Ecotect from all around the world. You can also import your own climate data if necessary. To the right of this page, you can confirm if the latitude and longitude are correct, and also set the time zone. Below this, you can specify which way is north, and the local terrain. This is used when performing thermal and ventilation calculations.

Figure 6. The Project page tab is used to load the correct weather data file for your project, as well as set the time zone and north orientation for the site.

Return to the 3D Editor page tab (note the north point shown on the modeling grid, now indicating the building orientation) and then switch to a Plan projection via the View menu. Then go to the Calculate menu and click on Prevailing Winds (see Figure 7).

Figure 7. The Prevailing Winds dialog box.

In the dialog box that appears, accept the default settings and click OK, and you will now see the Ecotect model overlaid with prevailing wind data for the entire year, as shown in Figure 8. This allows us to see that most of the winds are low speed and mainly from an easterly, and south, south-westerly direction. In order to maximise cooling using natural ventilation, we would want to orientate living spaces and openings to take advantage of these winds.

Figure 8. Prevailing wind data can be viewed as an overlay with the Ecotect model.

Of course, if you need further information, such as what times of the day these winds are present, this can be configured via the Prevailing Winds dialog box (see Figure 9). You can also view other climate data in relation to your model, such as wind temperature, rainfall and relative humidity. However, as different weather stations around the world have varying procedures for recording climate data, the Ecotect climate data file may not contain all of this information. Nonetheless, most will still contain sufficient data to be of value.

Figure 9. Ecotect includes a variety of other climatic data as well.

We can also begin examining the solar orientation and shading aspects of the model. While there are a number of programs that can display accurate shadows and shading in a 3D model, there are a few analysis features unique to Ecotect in this regard.

To reset the model view, press the F9 key, and then F8 to return to a perspective view. You may also want to resize the modeling grid to fit the model by clicking the Fit Grid to Objects button. Now go to the Display > Shadows menu. This displays the shadows that would be cast by the building on the ground plane. You can see that Ecotect uses different shades of grey to differentiate between shadows and sunlight penetrating or reflecting into a space. As can be seen in Figure 10, the proposed design has the kitchen, dining and living spaces orientated north, providing good solar penetration into these spaces.

Figure 10. Displaying the shadows on the Ecotect model.

We can also analyze the shadows and shading for particular days. Based on the geographic location specified, Ecotect automatically works out key analysis dates, such as the winter and summer solstice. Click the Set Current Time/Location button, and choose Winter Solstice, for example, as shown in Figure 11. The shadows update automatically, and you can adjust the time to the left of this button.

Figure 11. Ecotect records key analysis dates throughout the year, such as the winter and summer solstice.

Ecotect can also project a 3D stereographic sun-path diagram onto the model, as shown in Figure 12, which allows us to see the position of the sun in relation to the model. Click on the Shadow Settings control panel to the right of the main window. Check the Display Sun Path checkbox.  In the corresponding diagram overlay, click and drag the sun (or use the Up/Down buttons to the right of the Time field in the toolbar) to interactively adjust the shadows. Now also check the Annual Sun Path checkbox. You can adjust the time position of the sun as before, and hold down Shift while you drag the sun to change the date.

Figure 12. A sun-path diagram projected onto the Ecotect model can be a useful visual display for planning reports and submissions.

Reset the date and time to 12.00 June 21st (Winter Solstice for the southern hemisphere), and uncheck the Display Sun Path and Annual Sun Pathcheckboxes. In the Shadow Settings control panel, click the View from Sun Pos button, and then click on the Visualise page tab. The view of your model is reorientated as if you are standing on the Sun itself, looking back towards the Earth (see Figure 13). This allows you to visually analyze which surfaces are most exposed to the Sun at different times of the year, which could be used to determine the optimum locations for positioning solar panel arrays.

Figure 13. View from Sun position may at first seem esoteric, but allows you to gauge visually which model surfaces receive the greatest solar exposure for a particular date and time.

Lastly, overshadowing of adjacent properties is something that often needs to be addressed in an early schematic design. In Western Australia, for example, a proposed development cannot overshadow an adjacent site by more than 50% at 12 noon on the day of the Winter Solstice.

Under the Zone Management control panel, turn on the Outside zone. Three plane objects have been used to represent the site and adjacent properties. Select the two adjacent site objects, and under the Shadow Settings control panel, click the Shaded button to designate them as shaded surfaces. Now Ecotect only displays shadows on these objects, as shown in Figure 14.

Figure 14. After tagging the adjacent sites as shaded, projected shadows will only appear on these objects.

From a quick visual analysis, we can clearly see there will be no overshadowing issues for the property to the north, and that less than 50% of the southern property will be shaded at the specified time and date. However, if a more quantitative analysis was required, say for planning approval purposes, this can be generated even at this early stage of conceptual modeling. Select just the southern property, and go to the Calculate > Sun-Path Diagram menu. In a new window, you will see a more conventional version of a stereographic sun-path diagram, and in addition to this, the approximate shadow being cast onto the selected object. Expand the Shading Mask section to the right of the diagram, and then click on the Calculate Shading button. Set the dialog box that appears as shown in Figure 15, and then click OK.

Figure 15. Settings for the overshadowing calculations.

After a brief calculation period, the shading mask for the selected object is displayed on the sun-path diagram, along with a legend indicating the percentage of overshadowing that occurs (see Figure 16). In the bottom left hand corner, you can see that only around 23% of the adjacent site is overshadowed by the proposed development. In the main Ecotect window in the background, the test points are indicated with small green dots. Increasing the accuracy increases the number of testing points used.

Figure 16. The shading mask generated for the southern site, showing what percentage of overshadowing occurs on it.


I generally don’t find technology all that interesting unless it somehow helps me to be a better architect. Hopefully, this article has demonstrated just how useful Ecotect can be in the early stages of the design process. In future articles, we will examine how Ecotect can be continually used to analyze the performance of a proposed building, even during the production of construction drawings.

Issues such as climate change and diminishing resources are increasingly having a significant impact on the way in which we design and construct our built environment. As building design professionals, architects can no longer rely solely on intuition or generic ‘rules of thumb’ to design energy efficient buildings. Nor can we palm off these responsibilities to consultants at the end of the design phase, with a “just make it work somehow” attitude.

With tools such as Ecotect, architects are better empowered to make decisions regarding these matters, and can adopt a more holistic approach towards building design. Ultimately, this will result in more energy efficient buildings and a green, sustainable approach towards development, which can only be a good thing!