Dave's Top Tip: Custom Variables within VistaPro

Dave’s “top tip” 5

By using custom variables within VistaPro you can define your own particular result output. Let’s say VisaPro does not give you the exact combination of results required, leaving you to manually create these results within a spreadsheet. There could be a better way… 

Within VistaPro, you can take any of the results output (whether this is weather data, room setup and loads, building loads, energy or carbon result) and combine them using your own expression. With this you can create your own results variable, include these new results within all future simulations and also pass onto other colleagues.

Here are some simple examples:

• Considering the peak CO2 concentration for the classroom occupied period 
• Frequency and synopsis of operative temperature when the room is occupied
• Obtain the synopsis result for the amount of hours the air temperature is above 28^oC
• Obtain a result that considers multiple variables at the same time

The reason this top tip has come up is I was recently discussing the latest BB101 guidance with a client. They mentioned that a variable wasn’t easy to obtain and showed me the huge spreadsheet they used to extract the results they require from multiple annual results tables. The spreadsheet contained extracted results for particular times and then would finally calculate the Mean and Maximum values. I asked why they hadn’t just setup a custom result. Their answer: “A what?” A moment later, I’d shown them around the use, setup a sample for them and viewed the results. They were so happy they said this should be on my Top Tip List of things to do in the future – so here we are.

This very simple operation provides a far more efficient manner to get the required results. An example of this is not having to set up the same range test multiple times, rather, you can define this standard range test to be used within multiple rooms, iterations and models.

Custom variables can also get you results that could only be obtained with a mixture of outputting results in conjunction with a complex spreadsheet. An example of this is to look at results for only an occupied time allowing you use the synopsis function for the times you are interested in, then you can get results based on other existing variables, like the amount of people dissatisfied. In VistaPro you can easily get the amount of people in a room. You can also see the percentage of people dissatisfied, but you cannot see the actual number of people dissatisfied. Well, using these two results variables, you can create a single result that’s not possible without making a spreadsheet.

Another example is the CO2 concentration result. You can very easily extract your room’s peak concentration, but it’s less easy to find the peak within a certain time frame; doing this for every room at the same time would be quite a lot of work. Again, using the custom variables, you can very easily obtain your peak result for the occupied time.

If you are interested in custom variables, it’s very easy to start to understand and test the outcomes by following these few simple steps:

• Go to VistaPro Menu within the VistaPro application 
• Select Manage custom variables
• Add a new variable
• First use the drop down menus to list the variables you want to consider. These variables are assigned a letter to be used within your formulae
• Use the box below to input your formulae (using boolean algebra to control the variables)
• Further information can be found on possible functions and constants if you hover your mouse over the options to the right of the formulae input box

Example for air temperature during the occupied period:

• Set up Room variable Air Temperature as A
• Set up Room variable Number of People as B 
• Use these to setup your formulae IF(B>0.1,A,NAN)

The above formulae is saying: If B (Number of people) is above 0.1 (means is room is occupied) then you can display the air temperature, if not then do not display anything.

You can then select this new variable within the standard list of results and maybe show a graph for a week. All results will only take these results into consideration, so the new range tests and synopsis will give a different result than if you considered all results as they will only include the occupied times.

All these new variables you create are kept within a program data folder (example C:\ProgramData\ies\apps\VistaPro) as *.udv files. Once they are in this folder they will be available for any further simulations and they can also be passed to others for use within their machine.

I’m really interested to see if you use this function and if you do then I would love to know more. Please drop me an email and let me know your formulae, and what’s your reason for use. Maybe I could run another Top Tip release with a list of your favourites. 

If you want to find out further information on this subject then there is a VistaPro Custom Variables Help File. 

Contact sales@iesve.com for more details.

If you have any ideas or requests for Top Tips to help engineers get the most of VE please let Dave know: david.pierce@iesve.com