Worked Example 1 - Comparing HVAC Systems


Quite often, a building will assume the most common HVAC system out of familiarity and ease of design and installation but this can leave much more efficient options on the table. Sefaira can help you to rapidly compare the output from different systems on your building and see the steps required to make a step-change in your design.

End Output

The output will consist of a table of peak values for heating/cooling/energy and cost of your building with different systems. 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 loads are being supplied centrally and what loads are derived from zones here.

Setup of Comparison Matrix

  1. Build a model
  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 will keep all internal conditions and envelope the same, only changing the HVAC system. Here we have cloned 2 more concepts from the initial model that we uploaded.

For the first, you select 'Heating & Ventilation' and see that there is no cooling and the heating peak load is 276kW. Clicking on 'Clone' (beside the floor area) copies across the setup of the previous concept and allows another HVAC system to be selected. in this case we compare the same building with no cooling to one with fan coils and central outdoor air. Repeating the procedure we can compare these two concepts to one with VAV and central plant.



Note: the red/green % indicates the increase/decrease in any value versus the selected concept. Here we can see the changes when we select the second concept;


Explanation of Optimised Selection

Using this concept comparison matrix, the user can find the HVAC system which is optimised for their building. If cooling is required and energy cost is the driving metric then, in this case, FCU is the best option.

Peak Graphs 

This peak information can be further broken down using the graphs on the right;

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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