ASHRAE Ventilation vs PAS Systems
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September 09, 2009 | Category: Product Information
PURE AIR SYSTEMS
A Discussion on ANSI/ASHRAE Standard 62.2-2007
Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings
OLD STANDARD: The concept of utilizing mechanical ventilation as an effective method for reducing indoor air pollution in homes and small commercial buildings (two – story) has been considered an effective method to ventilate homes and minimize sources of indoor pollution. This concept applies to spaces intended for human occupancy within single-family houses and multifamily structures of three stories or fewer, including manufactured and modular houses.
PREMISE: The use of moderate to high volume self contained air filtration systems to allow for high rates of air filtration to reduce indoor air pollutants in occupied areas while also introducing small amounts outside, filtered fresh air for ventilation in-lieu of large amounts of mechanical ventilation as discussed in the ASHRAE 62.2-2007 standard.
IN THE BEGINNING
The use of natural ventilation in occupied areas has been around since people lived in caves. It is somewhat interesting to note that the method of ventilation for reduction of indoor air pollutants has not changed much since then.
The use of either natural ventilation ( such as opening up windows, doors or use of gravity vents) or mechanical ventilation such as fans, ducted vents with fans and mechanical HVAC equipment with the ability to introduce outside air have been primary methods of ventilation for years. This method was used for natural conditioning of the air temperature, reduction of stale air (removal of CO2) or reduction and/or removal of airborne pollutants.
There are a number of challenges with using outside air for ventilation. First, if you introduce outside air that is significantly above (hot) or below (cold) the inside ambient temperature you will increase or reduce the temperature and humidity levels in the occupied area and the energy requirements (and equipment costs) to maintain a comfortable temperature and humidity range become excessive. Second, outside air is not really fresh air. In today’s world no matter where you live the amount of contaminants and pollutants in the outside air preclude you from introducing any air from the outside unless it is properly filtered.
A MORE EFFECTIVE ENERGY EFFICIENT METHOD
Since its inception in 1985, Pure Air Systems HEPA based air filtration units were designed to be used to both filter the air and offer the option of introducing small amounts of outside, filtered fresh air for ventilation and reduction of CO2 and other airborne pollutants. The PAS systems can be used in conjunction with any type of forced air ducted heating/cooling system in the partial by-pass configuration or as stand alone units.
Page 2. Ventilation In Low-Rise Buildings:
The Pure Air Systems filtration units are all fan powered and range in air filtration volume from 350 CFM to 2000 CFM. These units incorporate an ECM energy efficient motor, forward curved blower, prefilter, carbon and certified 99.99% at 0.3 micron HEPA filter. The system is attached to the return air side of the HVAC system and a portion of the return air is brought in through the HEPA system (see image below) and continuously filtered.
A small amount of outside air (usually 50 to 100 CFM) is introduced directly ahead of the PAS unit. This small amount of air is naturally mixed with the ambient air from the return. Since the amount of outside air is much smaller (by percentage) than the amount of ambient air, even with extremely hot or cold outside air, the resultant mixed air temperature that is achieved through the natural mixing process delivered back to the HVAC system has a temperature differential of no more than 5 to 8 degrees F. from ambient. This means the amount of energy required to heat or cool this air back to the required temperature is minimal.
With the new tighter, energy efficient building techniques used today the need for some type of ventilation in occupied areas is necessary. However, with the need to reduce energy costs and meet some of the new LEED building certifications it is more important then ever that alternate methods of introducing outside air for ventilation be considered. The ventilation method utilized by Pure Air Systems is not only more energy efficient but provides a much greater reduction of airborne pollutants and better indoor air quality.
Pure Air Systems
6115 Guion Road
Indianapolis, IN 46254
Post Tags: ASHRAE indoor air quality ventilation
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About the Author: Don Musilli
My name is Don Musilli. I started Pure Air Systems in 1985 and then sold it in 2006. I continue to consult for PAS and write their blog and control their Twitter account. I also, on occasion, make changes to the website. The company is now almost 26 years old and has been a major player in offering commercial grade, high performance HEPA and Carbon based filtration systems for the commercial, institutional, industrial and residential markets.
I currently reside in Englewood, Florida where I write blogs and do social media marketing for a number of clients.
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