Exploring Whole House Filtration and Particulate Matter, with Aprilaire (Video)

Posted by: Rate It Green Team

In this interview with green builder Matt Hoots, Joseph Hillenmeyer with Aprilaire takes a deeper dive into whole-house air filtration and explores what we need to know about healthy air.  Awareness of filtration has grown in the last year particularly, but this is not a new topic for people who were already sensitive to pollens, dust mites, have other allergies, or who are more knowledgeable about health.

At a high level, Joseph explains that air purity is about the particulates in the air we breathe. Particulate matter, also known as PM or particle pollution, is a term which describes the mix of solid particles or liquid droplets of various sizes found in the air.  Great attention has been paid in recent years to PM2.5, or fine inhalable particles, which are generally 2.5 micrometers or smaller and pose the greatest health risk.  For comparison, the average human hair is approximately 70 micrometers in diameter - 30x the largest particle considered fine by this definition.  Particles of this size are able to travel deep into the human respiratory tract and lungs and can cause short term health effects including irritation, coughing, sneezing, runny nose, and shortness of breath, as well as longer term effects such as the worsening of certain medical conditions including asthma and heart disease, chronic bronchitis and heart disease.  People with breathing and heart challenges, children and the elderly may have increased sensitivity to PM2.5.  Outdoor PM sources include vehicle exhaust, other forms of combustion, power plants and even fires.  Indoor sources include cooking, fireplaces, peace heaters, smoking, and appliance combustion.  

As Joseph explains, "If it doesn’t go through a filter,  it’s going through your lungs...Let your HVAC system catch these things, not your lungs.” So what kind of filter is needed?  Joseph and Matt agree that the typical 1-inch blue filter we can buy at the local big box store and see though protects the HVAC system and are energy efficient as they allow quite a bit of airflow but are not designed for optimal human health protection.  

Indoor air quality can be surprisingly poor.  When we cook or run a fire, particulates are hanging in the air and not being exchanged with fresh air.  Interestingly, we have some visual awareness of particulate density.  When there’s less dust, and less particles in the air you can even see sometimes, such as when a ray of light hits some fine dust in the air, the air is generally more pure.  Filtration can get these particles out of the air before they enter your lungs.   

High filter efficiency starts at MERV, or Minimum Efficiency Reporting Value of 11, where the filters can catch mold spores and other airborne particles in the air such as hair spray, pets, and some bacteria. Filters that have a MERV rating of 13 and higher can trap even smaller particles, including viruses, and have been generating more interest and demand as filtration awareness increased.  MERV measures the performance of a filter when facing particles of .3 to 10 micrometers.  Higher MERV ratings mean that the filter is capturing a greater amount of particles with each pass, with a MERV filter capturing more than 95% of particles.    

It’s hard to say exactly what each MERV level catches, as particles vary even within types - not all bacteria are the same size, for example.  It is generally agreed that MERV 13 filters can catch PM2.5 microparticles.  MERV 13 is becoming a standard for the HVAC and home building industries, as this thicker MERV filter with more surface area will protect health while not sacrificing energy efficiency or performance of the equipment. 

Air exchange is another key term to understand.  An air exchange rate or "air changes per hour” refer to the number of times that existing air is replaced with fresh air in a given space. The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) has set guidelines for air changes per hour which vary by room - 5-6 for bedrooms, 7-8 for kitchens and 8-9 for laundry.  The recommended changes per hour are used by building professionals to calculate the required air floe in a room to ensure adequate air exchange per hour (room dimensions and depth multiplied and then divided by 60).  Air exchange is becoming even more important as homes are built increasingly energy efficient and “tight” to minimize energy losses.  Without sufficient air exchange, allergens and irritants can be trapped indoors and can affect occupant health.  

According to Joseph, portable air purifiers have a place when there is not a forced hot air system or where the indoor air quality isn’t great  and the space may be large or not controlled by the occupant, such as in an office without sufficient air exchange.  In these cases, the additional air changes provided can be helpful.  Consumers should look for high efficiency particulate, or HEPA filters, which capture 99.97% of airborne germs and also nonliving pollutants such as particular matter.  HEPA filters are not practical for whole-house filtration as they’d need more powerful fans than is practical) Consumers should look to confirm that PM 2.5 is captured by a filter, or that 1-3 micron sized particles are captured.  Another question is if the purifier releases ozone, which can be hazardous for human health and the environment. 

Whole house continuous filtration makes the most sense where the system can leverage and existing ductwork from a forced air heating or air-conditioning system.  Filters are installed in the return-air ductwork and trap particles as the air passes through.  If adding a filter to an existing system, it’s important to consult an HVAC (heating ventilation, and air conditioning) professional to make sure the filter is the best fit for health and that it also won’t have negative impact on the system. CFM or cubic feet per minute is a measure of how many cubic feet per minute of air a filter can effectively clean.  Typically, 100 CFM is needed for each square foot of space.  

Proper filter sizing is important, as a filter that is too small will restrict airflow and can even clog.  Increased resistance will then cause a drop in static pressure, which means that air will be circulating less effectively and the system overall will be less efficient.  This condition can result in added fan stress and increased energy bills, or can even burn out the fan and/or void the warranty.  

Proper installation also matters. If a filter is of poor quality or is not installed properly, and if there’s a way for air to go around the filter, it will, as air chooses the path of least resistance.  If air passes through some indented edge that wasn’t made well or that the user bent, then there’s no filtration, no forcing the air through the filter.  Insufficient filtration also occurs when the filter is left for too long.  All of the benchmarks and measurements only have meaning if air is actually forced through a filter… 

What questions do you have about filteration and indoor air quality?  Ask them here!

Also, click to read our other Aprilaire videos:

An Introduction to Aprilaire and Whole House Air Quality Systems (Video)

Reviewing the Top Benefits of Healthy #Air at #Home, with Aprilaire (Video)