The value of energy-efficient filters

Published:  15 November, 2005

filters
On average, energy accounts for an astounding 81% of the total life cycle of a filter system.

The energy consumption associated with an air filter can be 10 times its initial costs. COLIN HITCHdiscusses the implications.

In addition to removing contaminants from air that passes through the system to the building occupants and equipment, filters play a significant role in the energy consumed in operating the system. The energy us is based on the resistance of the filter to the air passing through it, so the lower the filter’s resistance, the lower the energy consumption.

Commodity

Unfortunately, many businesses look at the media used in their filters as a commodity that provides little differentiating performance value. Recent advances in filtration media technology show that this is not the case. However, because of the perceived commodity status, price has become the determining factor for building owners and managers when determining what type of filter and media to use.

It is important to understand that the cost of energy used by filters far outweighs the initial cost of the filter itself. Energy costs can be 10 times the initial filter cost for a standard pleated filters and four to five times the initial filter cost for higher-efficiency final filters. Therefore, with filters controlling most of the energy consumption of an HVAC system, companies should look to the filter itself as a method of conserving energy.

Conservation tool

Fortunately, there is a way to use filters as an energy-conservation tool. That is to consider the total life-cycle cost of the filter and the long-term impact on energy costs that a particular filter will have. More energy-efficient filters do not necessarily cost more, so energy savings can often be achieved without any investment at all. Life-cycle costs, energy costs and filter pressure drop should all come into play during the filter selection process.

The three major components of life-cycle cost for HVAC filters are initial investment and maintenance, energy consumption and disposal. On average, energy cost accounts for an astounding 81% of the total life cycle of a filter system. The initial investment and maintenance accounts for 18% and disposal accounts for 1%.

How can life-cycle costs of filters be applied to energy efficiency? Development of new materials has given the filter industry a chance to produce media with lower pressure-drop while maintaining high particle-capture efficiencies. Switching to a lower pressure-drop filter is one of the easiest changes for building owners and facility managers to make in an effort to reduce energy costs. That is because, with a lower pressure drop, the HVAC system motor needs to overcome less resistance to deliver the required airflow, therefore reducing its energy consumption.

Key criterion

Most building owners and facility managers would agree that filtration efficiency comes first. Beyond the efficiency rating, buyers and specifiers often use filter price as the next decision-making criteria. However, after examining life-cycle cost data and energy-saving data, it is evident that the key criterion should be energy consumption. When considering the energy costs of various filter technologies they should ask the following questions.

• What pressure-drop reduction offsets the difference in filter price?

• At what pressure-drop reduction would a filter upgrade pay for itself?

• At a given performance level, how much money could be saved by using a filter with a lower pressure drop?

• How much of my filter costs does that cost-saving offset?

The lowest-cost air-filtration system depends on many factors, including investment and maintenance costs, as well as ‘hidden’ costs such as energy, disposal and shrinkage due to damage.

Contrary to industry beliefs, high filtration efficiency no longer means high pressure drop. There are commercially available 95% efficiency synthetic-media filters with the same pressure drop as 65% efficiency glass media filters. They provide the ability to increase filtration efficiency by 30% without increasing energy cost at all.

Colin Hitch is a director with Jasun Filtration Plc, Riverside House, Parrett Way, Bridgewater, Somerset TA6 5LB.



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