UK Building Regulations
for Ventilation and 
Energy Conservation
Read VEETECH's
Response - 
Whatever Happened 
to "Keep it Simple - Stupid"?

  Ventilation Energy and Environmental Technology
                                     from VEETECH Ltd.              Updated 11th November  2009

Building Airtightness - Is Tight Right for British Homes?
Mechanical Ventilation Case Studies point to an 
Energy and Indoor Air Quality Disaster for Homes 

Tutorial  4    Solving the Flow Equations 

[See Disclaimer and Important Notes]

CLICK HERE for PHPAIDA The Interactive Ventilation Calculator Based on Opening Area combined with Wind, Stack and Mechanical Ventilation

Assuming a total of ‘j’ openings, the flow rate through each opening is solved by determining the internal pressure of the space or (in the case of a multi-zone building) each internal zone. This is determined by applying the Law of Conservation of Mass (i.e. the mass of flow into the building equals the mass of flow out or the sum of the flow equals zero). Thus the mass balance equation (and volume flow approximation) for j flow paths is given by:

These generally have to be solved by ‘iteration’ using a model such as PHPAIDA. The user must supply the pressure (due to stack and wind) for each flow path and the flow coefficient and flow exponent for each path. This leaves the internal pressure as the only unknown.

Direct solution is possible for very simple networks. Examples are given in Tutorial 5.

This completes Tutorial 4

Go To:

• Disclaimer and Important Notes;
  

• Tutorial 1 - Calculating Flow Rate through Openings - The Equations ;
  

• Tutorial 2 - Determining the natural driving forces (wind and temperature) ;
  

• Tutorial 3 - Developing a Flow Network and Introducing Mechanical Ventilation;
  

• Tutorial 4 - Solving the Flow Equations;
  

• Tutorial 5 - Simple Examples
  

• Tutorial 6 - The Online Algorithm PHPAIDA

[Return to Tutorials]