Low energy air filters are already saving enlightened companies millions of pounds in facilities running costs. Will Mann looks at the reasons for their rising popularity.

First there was the low-energy light bulb. Now, the low-energy air filter is becoming the ‘must-have’ for facilities managers looking to make quick energy savings and cut carbon emissions.  Due to improved technology, meaning potential cost savings of 30% a year, plus a changing regulatory framework, many companies are already making the switch to low-energy air filters, and in the process, saving themselves millions of pounds in facilities running costs.

This translates into a sizeable cost saving – given that energy represents 70% of an air filter’s life cycle cost, and that air filters account for 30% of the total operating cost of a heating, ventilating and air conditioning (HVAC) unit.

The key difference between conventional and low-energy air filters is the lower resistance they place on the fan motor of the air-handling unit (AHU), as Bill Wilkinson, Camfil Farr Managing Director, explains.

“A typical AHU handling 10m/3 per second of air would have 10 sets of air filters. The energy needed to drive the air through the filters continuously would be 50,000 KwH annually,” he explains.

“But as low-energy air filters are manufactured to maximise surface area , they place less resistance on the fan motor, meaning less energy is required; typically around 35,000 KwH per filter set each year, a 30% reduction.”

So what does this mean in energy costs? “The annual energy consumption of an air filter is usually around eight to 10 times the installation cost,” says Wilkinson. “Let’s say the tariff on energy is 10p per KwH. The AHU using conventional air filters would have annual energy costs of £5,000 or £500 per filter. By contrast, the annual cost for the AHU using low-energy would be just £3,500 or £350 per filter.”

Put in a wider context, such savings become even more significant.

“When you consider that there are around 1.2 million air filter sets installed in London alone, that £1,500 annual saving per filter translates into a potential saving of £180m each year across the capital simply by installing low energy air filters,” points out Wilkinson.

And that’s not including other, ‘incidental’ savings. Besides the reduction in energy costs, there are savings in labour of around 50% – because only half of as many filters need to be changed – and similar savings in waste disposal costs of old filters.

While the installation costs of a low-energy air filter are higher – as with low-energy light bulbs – the payback time is in months, or even weeks.

In any case, the upfront cost of switching is unlikely to cause facilities managers any financial headaches; because air filters are designed to be changed regularly, unlike other components within the AHU, upgrading to low-energy filters should not put extra pressure on capital budgets.

In addition to improved energy performance, Camfil Farr low-energy air filters also deliver better indoor air quality, because they trap smaller dust particles.

Already, many commercial buildings are feeling the benefits of installing low-energy air filters. Pharmaceutical giant Pfizer will save over £2m in running costs over the next five years at its 340-acre R&D campus in Sandwich, Kent, after upgrading to low energy air filters.

Pfizer initially appointed Camfil Farr to undertake an audit on several trial installations, which proved highly successful, with improved filter efficiency and reliability, meaning fewer maintenance interventions. This persuaded the pharmaceutical firm that it should replace the filter banks on AHUs in nine other key buildings.

Camfil Farr subsequently conducted a thorough assessment of the air handling plant in these buildings, which enabled it to accurately predict savings on filters, energy, labour and waste disposal.

The work carried out included filter framework modification and renewal, installation of new gauges, deep-cleaning of the AHUs, and fitting high efficiency/ low-energy F7 grade air filters that were manufactured at Camfil Farr’s Haslingden facility in Lancashire. (F7 is the minimum air filter efficiency standard required by European standard EN13779.)

According to David Mellon, capital projects manager at Pfizer’s Sandwich site, the project has cut air flow resistance – and therefore energy consumption – by 17%.

“Other benefits we can now see with this work,” he continues, “but that were not necessarily apparent until now, include reduced change frequency of the filters, and thus less waste disposal, reduced C02 emissions, and of course, reduced cost.”

The project has formed an important part of Pfizer’s site energy reduction initiatives.

Mellon adds: “Understanding the base criteria for running expensive HVAC plant is key to maintaining lean and agile facilities in the face of economic uncertainty and volatility in energy prices.”

So how quickly can we expect low-energy air filters to supplant their conventional counterparts?

From 1 September 2009 the conventional light bulb will not be manufactured; only the low-energy version will be available. It may not be long before the same is true of the low-energy air filter.

The changing regulatory framework will only encourage wider take-up of low-energy air filters.

In the UK, the Energy Performance of Buildings Directive makes inspections of air conditioning systems, and the production of a detailed report on their performance, mandatory for compliance.

Additionally, EN13779 (the European standard for ventilation) advises that the minimum filter particulate efficiency level required is F7, which is considered to deliver ‘moderate’ indoor air quality, when compared to outside air. F9, the maximum, is considered ‘high’ quality.

EN13053 (the European standard for AHU manufacturers) reinforces this advice by saying that air filters fitted to any unit should be minimum F7 grade.

Compliance with this legislation may mean substantial retrofitting for older commercial buildings in the UK. According to Camfil Farr, early feedback from inspections of air-conditioning systems reveal many are not up to the required standard . This suggests that they fall well short of those required to deliver the acceptable levels of air quality with optimum energy efficiency. On a site survey of a typical 20-year-old office building,  nearly all air filters were only F6 grade – considered ‘low’ quality air by EN 13779.

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