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Green potential of fans must not be overlooked

With increasing attention on the major components that drive heating and cooling systems, the role of various types of fans can be overlooked.

But ongoing technological developments make this an area where considerable cuts in energy usage can be achieved.

The latest Building Regulations and the Code For Sustainable Homes raise the bar on efficiency, says Vent-Axia residential product manager Ian Mitchell. He explains how mechanical ventilation with heat recovery (MVHR) provides an ideal carbon-cutting solution.

The Building Regulations introduced last year represent a key stage towards making all new homes zero carbon from 2016. Part L’s new Target Emission Rate (TER) demands a 25 per cent carbon emissions improvement over the 2006 regulations, in line with achieving Code for Sustainable Homes Level 3 - the requirement for private developments. Publicly funded housebuilders must attain Code Level 4 and achieve a 44 per cent reduction over 2006 levels.

Crucial role

Ventilation can play an important part in reaching these targets. To achieve Code Level 3, a home needs a 25 per cent better energy rating. To meet this, air permeability needs reducing to the minimum consistent with health requirements. As a result, changes to Part F publish guidelines for airtight properties with infiltration rates tighter than 5 m3h/m2 at 50pa, Mr Mitchell states.

The changes favour continuous ventilation, since it performs better in SAP, is easier to specify and easier to standardise, as trickle vents are not required. For continuous mechanical extract, System 3 approaches, the guidance removes the requirement for background ventilation in dwellings designed with infiltration rates above 5 m3h/m2.

These factors, combined with the Dwelling Emission Rate (DER) benefits of SAP Appendix Q, are set to boost the adoption of whole-house mechanical extract ventilation systems (MEV and dMEV) and MVHR systems at the expense of traditional, intermittent fans.

MVHR can be installed as whole-house solutions, combining supply and extract ventilation. Typically, warm, moist air is extracted through ducting and passed through the heat exchanger before being exhausted. Fresh incoming air is preheated via the heat exchanger.

MVHR technology ventilates the home in a very efficient way, saving energy, satisfying all relevant legislative requirements and making a big impact on cutting fuel bills, Mr Mitchell concludes.

The electric avenue

Electric motors are responsible for 40 per cent of the UK’s electricity consumption and fans account for 22 per cent of industrial motor energy consumption, says Robert Dann of Fläkt Woods. That means customers can make big savings if they know enough to recommend a product that is going to use less electricity.

By using EC fans, not only is energy consumption reduced significantly (compared to an AC fan) but also, with the addition of a variable speed control, operating noise can also be greatly reduced.

The motors are quiet and, by only operating according to demand, noise becomes much less intrusive, says Mr Dann.

For heat recovery units, small air handlers, central extract systems and others, upgrading from AC to EC fans can bring in new business and help save customers money.

A new breed of controls has been created that makes constant adjustments as the fans react to changing conditions throughout the system. This on-demand control means savings in running costs and reduced down time.

Inside the intelligent fan, a processor responds to input signals received from a range of sensors, which can include air quality sensors, motion detectors, thermostats and increases the extract or supply rate of the fan to match the demand.

All of these sensors come pre-wired and terminated with a plug, which is simply connected to the appropriate socket on the fan processor. This new generation of fans is offering many opportunities for contractors, who make the most of the potential when they know what to sell and why to sell it, says Mr Dann.

Blasts from the past

Johnson & Starley commercial director Sean O’Sullivan remembers when extract fans for kitchens and bathrooms, with some dwellings trickle vents for background ventilation, were the norm.

The extraction standards were 60 litres/second for kitchens and 15 for bathrooms. The fans were not always capable of meeting these when installed with a grille and subject to back pressure on a windy day with variable conditions, he recalls.

During the past five years there has been a plethora of regulatory updates, standards, guidance documents and compliance guides, which will become even more stringent.

We currently have Part F of the Building Regulations but this is affected by the energy requirements of Part L. Then there are the supporting documents including the Domestic Building Services Compliance Guide and the Domestic Ventilation Compliance Guide.

Installers now have to complete a commissioning procedure and log the balancing figures, which will lead to better installations, says Mr O’Sullivan. There has also been growth in ventilation options from the single extract fan to sophisticated MVHR.

As houses become more air tight they also become much quieter, requiring ventilation systems to deliver air at much reduced air noise levels.

Regulations and guidance documents were previously issued without much consultation, but now, through the trade associations, these are consulted upon and the industry has provided new initiatives and innovations.

The issue is to educate householders about the importance of ventilation in their homes, as in the future it will become the dominant system within the home.

Don’t omit emitters

The government’s Green Deal and the Renewable Heat Incentive have both been key factors to the growing popularity of heat pumps, says Smith’s Environmental Products sales and marketing director Jim Bennett. However, more attention should be paid to the efficiency of heat emitters connected to them.

Suitable for both existing and new build domestic or small commercial properties, fan convectors use simple and proven technology to put heat where required, when required, ensuring good air temperature distribution.

Their low water content, utilising a heat exchanger holding just 5 per cent of the water required for an equivalent output radiator, enables them to run at lower water temperatures used by heat pumps, which means that any heat pump attached to a fan convector is able to run at its maximum efficiency, he states.

The published COP of a heat pump is around 4.0, given at 35 deg C water temperature; however, every one degree rise in water temperature reduces its efficiency by 2.5 per cent. As fan convectors are able to operate at these low temperatures the heat pump will always be running at close to optimum efficiency. In stark contrast, this is not the case with natural convectors, such as radiators.

To be truly efficient, emitters on the end of heating systems need to be as ‘green’ as the heat pump at its source. With the flaws of radiators increasingly recognised, fan convectors are growing in popularity, especially when efficient emitters are required to run from low temperature, renewable systems.

As heat pumps continue to evolve and grow in popularity, fan convectors are the only economically viable, energy-efficient heat emitter available to complete these ‘green’ systems, says Mr Bennett.