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Ventilation strategies

We are building an experimental facility on the BRANZ site to investigate different types of ventilation systems. How does their performance depend on building airtightness?

The systems included in this research are:

  • supply-only systems
  • balanced systems
  • systems with heat recovery.

We are building our experimental house so that it is initially extremely airtight - one air exchange per hour at a pressure difference between indoors and outdoors of 50 Pascal. This is equivalent to an opening in the house of just 85 mm diameter. We can then add variable vents to increase the air leakage in a controlled manner.

We will be using a tracer gas detection system to measure the movement of air and contaminants such as moisture.

The outcome of this project will be ventilation systems that operate with higher efficiency under a wider range of conditions.

Update April 2014

Out test house is now operational, and we are in the process of measuring the effectiveness of different ventilation configurations. At this point in time, the three ventilation configurations and their combination we're investigating are:

  • a supply-only ventilation system with standard 3 supply ports
  • three passive stacks
  • wind-driven infiltration through adventitious openings.

We plan to add a mechanical ventilation system later this year, which operates a fan that will extract air from the house.

As we are particularly interested in the effectiveness of removing moisture, we are controlling the humidity in the house using three humidifiers. We are simulating the humidity profile of two occupants, which includes cooking, showering and breathing. At the moment, the occupant profile assumes that the occupants are a professional couple who go to work during the day. However, other profiles can be investigated too.

With this set-up, we have been able to achieve moisture loads that are observable in many New Zealand homes, with early morning condensation on windows and some mould growth (see picture). Achieving these conditions is important in order to measure the moisture removal effectiveness of ventilation configurations based on moisture levels observed in New Zealand homes.

Mould growth.jpg