Robustness Applet: This is an embedded interactive Java applet. Simply select any of the arrows at the left or right edges of the graph with the left mouse button and drag them inwards to restrict the result set by that value range.

Mouse Controls - Click & Drag

To interact with the graph, simply click and drag the ends of each parameter/result slider to narrow the filter gap. Clicking close to the lower value will adjust that side whilst clicking near the upper value will the adjust that. Clicking within the gap itself will allow you to drag the gap itself (ie: both values relative to each other) to the left and right.

What the Graph Shows

The sliders running horizontally across the graph show the type and range of parameter/result values used in the calculations. Parameter sliders basically show the design characteristics set before the calculation and are displayed in orange. The results sliders represent the actual calculated performance criteria obtained after the calculation run and are displayed in blue.

Each coloured line running down the graph shows an individual calculation run. Its position as it passes through each slider is the actual parameter value it was assigned and the result values that were calculated for that particular set of parameters.

By dragging a slider you effectively create a filter that hides those calculation runs that do not pass through that particular range of parameter or criteria values.

What to Look For

The aim of using a graph like this is to visually search for relationships between different parameters and the results they produce. For example, in the above graph you could narrow the Heating and Cooling Load results to a very low value and then potentially see several run lines that show mid-range U-VALUE but high SHGC (Solar Heat Gain Coefficient) parameters. This would mean that you could be a bit flexible in the types of wall and roof fabric within the building and still achieve the low heating and cooling loads you want, as long as you used highly effective solar control glass and kept the other design parameters around the values shown in each still-visible run line.

Why is it called a Robustness Calculator

By performing a large number of runs using very different parameter values, it is possible to quickly investigate a wide range of different design configurations. For example, once you have established that mid-range U-VALUE and high SHGC parameters may work, you need to look closely at the other parameter values for each still-visible run line.

If, for example, they all run through a very tight range of Window Ratio value, then the design will likely be very sensitive to the overall amount of glazing and you will have to get this right in order to meet your criteria. Alternatively, if they vary widely over the entire range of another parameter, then there is a chance that even a slight variation in this within the ‘as-built’ design may completely nullify the effect you were aiming for.

You could also manipulate the U-VALUE gap back and forth in order to see just how sensitive the results are to variations in this particular parameter. If the design is relatively robust, the result values won’t jump around all over the place as you make small changes to this value. You can then quickly develop an understanding of the reasonable range of values that will achieve your performance objectives. If the results are highly sensitive to small changes in parameter values, that it is likely that the performance of the built building will be too. This means that the design is not particularly robust so you will need to take particular care to ensure that the final ‘as-built’ design parameters very closely meet what you intended.


30 November, 2009 - 22:44Olivier Pennetier

This is exciting stuff Andrew :) Also, the interactive charts for the WeatherTool (example) are very promising too.

Click here to comment on this page.