Jon Hill, technical manager of Polypipe Ventilation, examines pod ventilation systems.
When designing a new house, ventilation should be at the heart of an integrated design approach to achieve energy efficiency. Also with more stringent building regulations and the Code for Sustainable Homes, legislation is driving specifiers to search for increasingly energy-efficient solutions.

For these reasons - the desire to achieve energy efficiency and the complexity of designing and fitting a good ventilation system - an increasing number of energy-efficient ducting systems are being used in bathroom pods.

It is important that a duct system is specified that maximises the energy-efficiency of the building. Highly engineered and consistent duct profiles are vital in achieving the required levels of efficiency as they ensure that air and moisture leakage are practically eliminated.

For those unfamiliar with the term, a pod is a prefabricated module completely fitted out with all the equipment and services needed for a bathroom, including the ventilation system. The pod is then delivered to site ready to 'plug in' to the building. Such a system allows for standardisation and prefabrication to improve quality, efficiency, health and safety (with less on-site work) and easy maintenance and replacement.

Pods are particularly suited to larger residential developments that have repeatability on the design, such as student accommodation and, more recently MoD accommodation.

If you do decide to venture down the pod route you should be aware of three key issues that need to be addressed, in addition to the standard ventilation requirements of Building Regulations.

The first of these is the likely need for a more powerful centrifugal fan in the pod, as the duct run is likely to be longer than in a traditional on-site installation.

The second is the need to have fire protection for the ducting. This involves the installation of a specialised intumescent product - such as our own FireBrake - around the ducting. This material reacts to fire and rapidly expands, stopping the spread of the fire through the ducting by providing a 100 per cent closed fire stop plug. It's an important safety measure.


The third and last consideration is ironically brought about by the quality of the pod ventilation design and build. The pods are built in a factory to very tight tolerances, but the property itself is extremely unlikely to match those exacting tolerances. This often leads to a misalignment of the pod to the building - it is almost unavoidable - so you need to be able to build a degree of flexibility into the pod ventilation system.

This can be done using a flexible hose or a specialist piece of rigid ducting that contains a flexible section. The hose is the cheapest option but is far too easy to damage, which would slow the air flow down and ruin the efficiency of your carefully prefabricated pod ventilation system. Instead, use a highly engineered rigid ducting with a flexible section, such as the Domus Universal Duct which is a purpose made blow-moulded synthetic flexible section which can be simply adjusted by hand between 0-45° in either a vertical or horizontal plane.

The latter provides a more professional finish than flexible hose and also offers improved airflow characteristics, helping to meet the good practice guide in Approved Document F of the building regulations.