What is Hybrid Ventilation?


Hybrid ventilation is the term most commonly used to describe schemes where the ventilation is neither entirely natural, nor entirely mechanical. The designer has taken a pragmatic approach and has opted, not for the purest or simplest strategy, but for the best solution to meet the ventilation needs of the space, whilst minimising the cost, maintenance and energy consumption implications.

For example, the Breathing Buildings NVHR system uses efficient centrifugal fans to achieve hybrid mixing ventilation in a small form-factor product. The design works with opening windows to assist and augment a predominantly natural ventilation strategy – thereby enabling a low-energy solution which works all year round, and can be used reliably in single-sided rooms.

Very few modern buildings are purely naturally ventilated. From the humble kitchen or toilet extract fan, to the grandest of air handling units, all buildings have some form of mechanical ventilation. In the same way, all well-designed buildings will have some form of natural ventilation; low-level supply with high-level extract, mechanical ventilation with open-able windows, or separate zones with natural and mechanical ventilation working independently.

hybrid ventilation nvhr winter

In terms of occupant comfort, a hybrid ventilation strategy, sometimes called mixed-mode ventilation, is a very attractive concept. A scheme designed to use natural ventilation for the majority of occupied hours can be assisted or augmented by mechanical systems under peak heating or cooling conditions. In principle, this hybrid solution is able to accommodate greater extremes of internal heat gains and external temperature fluctuations than can be handled by a purely natural ventilation strategy. The result is that energy consumption is minimised under normal day-to-day conditions, whilst ensuring sufficient ventilation capacity under a wide range internal/external scenarios.

As sustainable building practitioners, we all want to design low or zero-energy buildings. But, as discussed in a previous Breathing Buildings blog post, whilst saving energy is an essential and admirable aim, the main focus is simply about designing better buildings!

An excellent resource for information on hybrid ventilation is the website of the IEA Hybvent study, and the accompanying free-to-download booklet “Principles of Hybrid Ventilation”, edited by Per Heiselberg.

To discuss how we can assist you in designing the best ventilation strategy for your building, contact the Breathing Buildings design team by emailing info@breathingbuildings.com, or give us a call on 01223 450 060