Performance of a Demand Controlled Mechanical Extract Ventilation System

Session 15 Paper 3, CIBSE Technical Symposium, Liverpool John Moores University, Liverpool
11-12 April 2013

The main aim of ventilation is to guarantee a good indoor air quality, related to the energy consumed for heating and fan(s). Active or passive heat recovery systems seem to focus on the reduction of heating consumption at the expense of fan electricity consumption and maintenance. In this study, a demand controlled mechanical extract ventilation (DCV) system of Renson (DCV1), based on natural supply in the habitable rooms and mechanical extraction in the wet rooms (or even the bedrooms (DCV2)) was analysed for one year by means of multi-zone Contam simulations on a reference detached house and measurements on-site and compared with a standard MEV and mechanical extract ventilation systems with heat recovery (MVHR). To this end, IAQ, total energy consumption, CO2-emissions and total cost of the systems are determined. The results show that DCV systems with increased supply air flow rates or direct mechanical extract from bedrooms can significantly improve IAQ, while reducing total energy consumption compared to MEV. Applying DCV reduces primary heating energy consumption and yearly fan electricity consumption at most 65 to 50% compared to MEV. Total operational energy costs and CO2-emissions of DCV are similar when compared to MVHR. Total costs of DCV systems over 15 years are smaller when compared to MVHR due to lower investment and maintenance costs.