LETTER: In a new build, should I consider a decentralised vs a centralised ventilation system? Can it save on costs or are there any other benefits?
Q: I would like to install a mechanical ventilation with heat recovery (MVHR) system in the house I’m building and have been looking around at centralised systems, but today I got a quote for a decentralised system. I imagine for a new build (approx. 270 sqm), a centralised system is the better option but I haven’t been able to find much comparisons online specific to installing in a house. Would you have any insights or opinions on it?
Paula says: The choice between MVHR and decentralised ventilation will depend on factors such as your house design, energy efficiency goals, and the level of control and complexity desired. Both systems aim to provide adequate ventilation while managing energy consumption and indoor air quality.
The key element of MVHR is its ability to recover heat from the exhausted air, helping contribute to a comfortable indoor temperature while reducing energy costs. Careful design and installation is essential to ensure system operates efficiently. It is the system most typically used in houses that are being built airtight as there are no breakout points in the envelope of the home and provides balanced ventilation.
Decentralised ventilation is localised per room, as opposed to whole house balanced ventilation. Installation is easier than MVHR and may be more suitable for renovations/ extensions and retrofitting into existing buildings. There are 3 types of decentralised systems:
Demand Controlled Ventilation (DCV) adjusts the rate of fresh air ventilation depending on the number of occupants or level of pollutants in the room. The ventilation rate therefore fluctuates. There is no heat recovery element. DCV systems can struggle to meet performance in larger properties. There are breakout points in every room, but It is a simple means of ventilating a home.
Decentralised Mechanical Extract Ventilation (DMEV) are continuous running humidity sensing fans placed in each wetroom. These work in conjunction with indow trickle vents. This combination doesn’t provide filtered air, or any heat recovery element, but will provide adequate ventilation.
Single Room Heat Recovery units are primarily a retrofit / remedial ventilation product to help alleviate issues in individual rooms but are also used for small extensions or renovations. It wouldn’t be cost effective to install these units in every room in a new build home and the heat recovery element wouldn’t be as good as a centralised MVHR system.
