This section is explained in the Health Canada's Reducing Radon Levels in Existing Homes: A Canadian Guide for Professional Contractors, Section 4.2 Feasibility Test.

 

Reference from the National Standard of Canada: Radon Mitigation options for existing low-rise residential buildings: P29-149-012-2017-eng.pdf  

5.1.1 Feasibility test prior to installation:

A “pressure field extension test” (i.e. communication test) shall be used to determine the number of suction points and the fan size needed for an effective system.  A scheme of the communication testing results shall be documented and provided in the Homeowner radon mitigation system package. (see 7.2)

Step 1: Design Suction Pressure - This is where you take the natural pressure across the slab and multiply it by a temperature adjustment factor to get your target design pressure.

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Step 2: Design Airflow - This is where we determine the target airflow that would be required to achieve the design pressure from Step 1 at the furthest/weakest test hole.

 

Design Airflow =  Vacuum flow X  (Design Pressure / Observed Pressure)

Step 3: Target Cavity Pressure - This is where we determine what the design cavity pressure would be if you achieved your design airflow.  Cavity pressure is 1 of 3 pressures that your radon fan will have to overcome.

Target Cavity Pressure = Observed Pressure Change X (Design Airflow/Observed Airflow)^2

Step 4: Piping Resistance - This is where you calculate the pressure drop for the piping components.  This example is for 4” 100mm pipe.

Step 5: Determine Velocity Pressure (VP) – This is where you calculate the dynamic head based on your design airflow.

Step 6: Determine Dynamic Piping Resistance - This is where you calculate the total dynamic resistance of your piping components at your target air flow.

 

Dynamic Resistance = Velocity Pressure X Total Piping Resistance

Step 7: Total System Resistance – This is the sum of the dynamic piping resistance, the cavity pressure and the interior/exterior pressure difference that your fan will need to overcome to achieve the design airflow.