David Treharne, Senior Engineer at Domus Ventilation, explains the different extract fans available and looks at the potential sales opportunities.

Intermittent extract fans are a cost-effective, easy to install, simple to operate method of bathroom and kitchen ventilation that everyone is familiar with.  They also represent an added sales opportunity if you know which type of fan works best where.

There are essentially two types of intermittent extract fans – Axial and Centrifugal - each designed to perform best under well-defined situations. 

Axial Fans

Axial fans are designed to work with short duct runs, typically no more than 1.5m, which connect directly to an external outlet or grille.  Most kitchens and bathrooms with an external wall are suitable for Axial fans.  They incorporate impellers that force air to move parallel to the shaft around which the impellers rotate.

These are the simplest fan to install so can be fitted by anyone.  Ask any customer buying kitchen or bathroom products if they need a fan.  Even if there’s one in place, it’s a simple and low-cost job to replace what may well be an old, ugly, dirty one that may blight a bathroom/kitchen makeover.

Centrifugal Fans

For longer duct runs, Centrifugal fans are the preferred option.  These force air to move at right angles to the intake of the fan using centrifugal force.  They produce more pressure to overcome resistance encountered in longer duct runs – normally up to a maximum run of 6m.  Typically, they are quieter than Axial fans, but are more expensive.

Inline Fans

In addition to standard Centrifugal and Axial fans, there are also duct-mounted Inline fans which come in both formats, as well as mixed flow models (most frequently used in longer duct runs up to 6m). 

Unlike standard fans, Inline fans are not installed within the room itself, but slightly removed, such as in the ceiling void or attic, connected to the room via ducting mounted with a decorative grille at the end.  There is also the option to incorporate a ceiling light within the grille.  Due to their discreet location they are ideal for installation in showers.  More often than not they are sold in installer-friendly kits which make for a very easy sale. 

Clearly, Inline fans involve extra installation work and are often best-suited to new builds and major refurbishment projects.

Sorting the Wheat from the Chaff

There are a multitude of fans in the market place, so how to do you decide which brands to stock / recommend?  I would suggest focussing on the following key factors: energy-efficiency, range of available accessories/control options, noise and aesthetics.

Starting with energy-efficiency, ensure a fan meets Building Regulations Part L which requires Specific Fan Power (SFP) be no higher than 0.5 Watts per litre per second (W/l/s).  Of course that’s a minimum requirement and there are fans in the market that operate at lower energy consumption rates, such as Domus Ventilation’s Sapphire fans which have an SFP down to just 0.19W/(l/s).  In addition, check the fan’s energy consumption in standby mode as some use an extra 10-20% of the overall power used when in standby.  Domus Ventilations’ Sapphire range of 100mm Axial fans have been designed to use up to 70% less power when in standby mode than other low-energy fans.

The range of compatible fan accessories is important as it provides your customers with greater flexibility and choice, and you with added potential sales.  Virtually all manufacturers offer an automatic shutter to prevent backdraught but less provide a good range of control options.  There are the straightforward timer and pull cord options through to more advanced humidity control options that are capable of identifying and reacting to a significant change in humidity, plus PIR based controls that activate the fan on the detection of movement.  An override facility should be considered, maybe in the form of an overrun timer, most often set to deactivate the fan after a set time after the light has been switched off.

That brings us to noise and appearance.  A fan that operates down to 32dB(A) is a quiet fan, but noise can still be generated if the ducting used with it is poorly manufactured or incorrectly fitted.  Advise customers to buy quality ducting to avoid this (another upsell opportunity!); by this I mean ducting with exacting tolerances, i.e. a good fit, that doesn’t bow, look concave or have uneven wall thicknesses.  For the best quality ducting, opt for a system which has been third party tested for end-to-end system performance.

The fan will be visible so it should look good.  Stocking a mixture of models that are discrete / unobtrusive and others that are adaptable to compliment a variety of decors (e.g. with interchangeable facias) is sensible for customer choice.  

The job of fitting extract fans falls between a variety of different trades, including ventilation installers, electricians and builders.  As a result, it can be overlooked.  If you have a customer buying bathroom and kitchen products, remind them about the fan and offer advice on the type; you’ll have a happy customer....maybe even a fan....