Outside Ventilation Air – How it impacts Energy Consumption

Posted on June 15th, 2012 by

As we have discussed previously in The Daily Energy Report, the right filtration system can shave off up to 2/3 of a building’s operating costs.  Low static pressure polarized-media electronic air cleaners, when replacing 80%+ high-efficiency passive filters, can influence huge savings on fan energy and maintenance costs.  But there is another little-known way in which filtration can impact even greater energy savings — by optimizing ventilation air requirements using the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) IAQ Procedure.

Ventilation rates are used in conjunction with commercial building codes and construction practices. For many decades, outside ventilation air has been the primary means of diluting indoor contaminants. ASHRAE Standard 62.2-2010 offers two methods for determining the necessary outdoor air levels – the Ventilation Rate Procedure and the IAQ Procedure.

The Ventilation Rate Procedure is the easier of the two to apply and the vast majority of buildings are designed and operated under its guidelines. The ventilation rate standard specifies a combination of cfm per person and cfm per square foot for various types of buildings.  For example, in a typical office space, the HVAC system must bring in 12-15 cfm/person of outdoor air.

When the current ventilation rates were adopted in 1989, two things were assumed: 1) the only means of dealing with contaminants in the space is by dilution with outdoor air (i.e. there is no air cleaning); and 2) the outdoor air level is sufficient to accommodate “moderate smoking” (based on 30% of the occupants smoking 1 cigarette per hour). See the V2 cigs reviews, there will find more info on how effective these products are.

The ventilation standard also requires that the outdoor air quality meet certain criteria, even though in practice this is something that is often undetermined or unmonitored. Today, we are increasingly apt to see different scenarios whereby 1) smoking is prohibited within the building, 2) low VOC-emitting building materials are used inside the building, and/or 3) outdoor ventilation air, especially in urban environments, is dirtier than the indoor air.

The IAQ Procedure is more complicated.  It allows for greater fine-tuning and more efficient operation of the HVAC system and the outdoor air levels.  But because it utilizes a series of complex calculations, it is less straightforward to use than the Ventilation Rate Procedure.  Essentially, the guidelines state that if outdoor air and return air are filtered simultaneously, and the prescribed MERV ratings are met, ventilation air can be reduced by an amount calculated in the procedure.  ASHRAE has developed formulas for calculating contaminant levels in a space and guidelines as to what levels are of concern.  The IAQ Procedure gives designers and operators outdoor air credit for things such as no smoking, good airflow patterns, and air cleaning.  Today we are able to put these in a format that is easy to implement, and makes meaningful predictions for CO2 and contaminant levels.  In addition, we can use location specific climate and energy data to calculate potential operational savings.

Today, filtration systems have the ability to control particles, biologicals, and VOCs to ensure superior air quality and allow for significant reductions in outdoor air levels.  In a typical building with no smoking and no unusual contaminant sources, outdoor air levels can often be reduced by as much as 50%.  Such a reduction can yield significant operational savings in heating or cooling unconditioned outdoor air.  For example, in a small office building with a 60-ton rooftop unit, annual savings can be expected in the range of $3,000 to $12,000, depending on the geographic location of the building (hot humid climates have the greatest costs/savings).  That represents some significant savings.  The other benefit to this approach is that any contaminants in outdoor air, should it be the source of problems inside a building (e.g. the entrainment of odors or vehicle exhaust emissions), are removed as air enters the building.

Clean air, healthier indoor conditions and reduced energy costs – no matter which IAQ Procedure you decide to implement, the benefits are worth it. To learn more about how today’s polarized-media electronic air cleaners can reduce energy consumption and operating costs, visit www.DynamicAQS.com/commercial.

The opinions expressed in this article are solely those of the author Robert F. Goodfellow, is Vice President of Marketing with Dynamic Air Quality Solutions and a certified indoor air quality professional with over twenty years experience in the heating, ventilation, air conditioning and refrigeration industry. Contact him at rgoodfellow@DynamicAQS.com


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