Worked Example 2 - Sizing HVAC Systems


If information about plant size and even coils/risers etc could be discussed upfront, designers could avoid changing fundamental coordination decisions multiple times over a project. Sefaira can help you to rapidly compare the output from different systems and configurations on your building and see the steps required to make a step-change in your design. 

A great example could be cutting the plant and riser size in half by optimising the facade in particular areas. Sefaira allows the user to do this with a location-specific model and hence justify plant space and focus design decisions where they are most needed.

End Output

The output will consist of a spreadsheet showing peak coil loads for each zone. If particular systems require deeper understanding or export of results, Sefaira can provide those here. Along the way you can see a breakdown of what total loads are being supplied centrally and what total loads are derived from zones here.

Setup of Comparison Matrix

  1. Build a model following our guidelines,
  2. Upload that model using the upload button in the plugin,
  3. Choose Create Sefaira Systems Project once the browser opens,
  4. Enter relevant project information,
  5. Choose Baseline and Internal Conditions for the project from drop-down menus on the left of the Systems project page,
  6. Select HVAC system type from the drop-down menu in the Concept comparison matrix

At the top of the systems project page there is a matrix which contains the results of each model setup under different conditions. In this example, we have looked at some different systems on the same massing previously and now we upload a zoned massing to see the sizing of the system.



We can see that for the 'Zoned FCUs' the peak cooling is 187.5kW but what does that mean in terms of coils in each zone. To find out, we can click the green 'Excel' button beside the word 'Downloads'. This will open a csv file showing the peak loads per zone from which we can size our system;




Explanation of Optimised Selection


Using this zone sizing output, the user can find the zones which require the highest peaks and optimise the design further. For example, here we can see L001_P11,12&18 have significantly higher peaks than the other zones. This may be deliberate and expected due to higher internal loads or may be due to poor facade design in those zones.

If the design seems optimised, this information can be directly converted into a sizing cut sheet for each zone.



Example Model

The attached models can be opened and uploaded to follow the procedure described above. For any further questions, contact your dedicated customer success representative or email


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