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The Heating Ventilation and Air Conditioning (HVAC) system of a building plays a huge part in the building’s overall energy consumption and the health and welfare of its occupants. According to the US Department of Energy, HVAC accounts for 40 to 60% of the energy used in US commercial and residential buildings. As prices soar and environmental pressures increase, it is wise to look to HVAC systems as a way of cutting down on energy consumption. 35847
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Kent Peterson, President-Elect of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) says: “There are ample opportunities for building managers to save 30% of the energy consumed in most buildings today. ASHRAE, the [US] Department of Energy and the Environmental Protection Agency [EPA] are all working to help educate building owners and operators on methods to reduce building energy consumption.”Peterson adds: “The first step is for a building manager to assess the performance of their building. In the US, the EPA Energy Star program provides one method to determine building performance with their online Portfolio Manager benchmarking tool.”ASHRAE supplies technical information to engineers and other professionals. It also writes standards and guidelines in its field of expertise to guide industry in the delivery of goods and services to the public. Their Energy Standard for Buildings Except Low-Rise Residential Buildings, sets the minimum energy efficiency required by most building codes. To take the standard even further, ASHRAE, in conjunction with the American Institute of Architects (AIA) and other organizations, has developed Advanced Energy Design Guide for Small Office Buildings, which provides a “sensible approach” and all the tools needed to create energy-efficient office buildings of up to 20,000 square feet.The EPA, in conjunction with stakeholders, developed the energy rating as a screening tool; it does not by itself explain why a building performs a certain way, or how to change the building’s performance. It does, however, help organizations assess performance and identify those buildings that offer the best opportunities for improvement and recognition.No rules, no standards, just maths?
A HVAC system refers to the equipment, distribution network, and terminals that provide either collectively or inpidually the heating, ventilating, or air-conditioning processes to a building. In assessing the energy efficiency of a building, it is necessary to evaluate the efficiency of a HVAC system, and identify areas for improvement. Filtration equipment manufacturer SPX Air Filtration says there are no hard and fast rules for evaluating the efficiency of a system; it’s a matter of simple mathematics. Paul Sennett, senior vice president, business development and marketing, elaborates: “There is a direct correlation between pressure drop (resistance to air flow through a filter) and the energy that is consumed. In simple terms the fan moving the air has to work harder to get it through the filter if its resistance (pressure drop) is higher. The simplest way to improve energy efficiency in a HVAC system is to reduce the pressure drop over the filters.”Sennett says that it is easy to change a filter to a lower pressure drop, the difficulty is selecting a filter with lower pressure drop, but the same efficiency (ability to capture particles). This is the job of the filter manufacturer; to design media and filters, which maintain the efficiency whilst improving the pressure drop. “No standards are in place for this because it is simple maths,” he continues. “The broader question is that of 'life cycle cost' [LCC]. It would be easy to select a filter which reduces the energy consumption, but if the cost of the filter is very high, the filter does not last as long and the disposal costs are also high, then the entire cost of the filter throughout its life, becomes unsustainable.”Assessing the calculation of LCC is the job of trade bodies such as Eurovent (in Europe) as well as companies. Sennett says energy is typically 80% of the cost of running an air conditioning system and filter costs represent less than 20%, so it is clear that improvements in energy consumption – even if the filter cost is higher – will almost certainly be economically sensible given this ratio. Calculating LCC for the full pictureAlthough the maths involved in assessing the efficiency of a filter in a HVAC system is fairly simple, the calculation of LCC can take some time, as it should include a full picture of the building’s costs. SPX Air Filtration has developed a piece of software to help customers calculate the system’s energy consumption given different scenarios of filter choice. The software takes specific information from the customer, some assumptions from standard Western European commercial buildings and then models the options and selects the optimum solution for LCC.In the US, Dave Matela, CAFS, Kimberly-Clark Filtration Products, says: “To look at HVAC filters as energy conservation tools, it’s first important to understand that the cost of energy used by filters far outweighs the price of the filter itself. In fact, energy costs can be ten times the initial filter price for a standard pleated filter and four to five times the initial filter price for a higher efficiency final filter.” Kimberly-Clark provides an interactive online energy calculator for professionals interested in seeing how the energy consumption of their HVAC filters compares with other filters. Matela says switching to a filter with a lower airflow resistance is one of the easiest changes to make to reduce HVAC system energy costs. But he adds: “Alternatively, a building owner may look to improve indoor air quality by selecting a filter which provides higher filtration efficiency at the same airflow resistance as the original filter.