Heating and Ventilation

Guide to indoor air quality for multi-family units

Understand why indoor air quality has become a crucial element of living environment building operations.

By Tim Milam, PE September 7, 2021
Courtesy: Jordan & Skala Engineers

Indoor air quality has become a crucial element of living environment building operations, especially in multifamily buildings. Multifamily and mixed-use buildings must meet the demands of all the different tenants inhabiting the space.  Because the building codes are requiring a much tighter envelope, the design and delivery of proper ventilation inside the occupied space and the quality of that air becomes immensely important.

So what is indoor air quality (IAQ)?  The United States Environmental Protection Agency defines indoor air quality as “the air quality within and around buildings and structures, especially as it relates to the health and comfort of building occupants.”  Essentially, IAQ is the measure of the cleanliness and purity of the air inside a space when compared to fresh outdoor air.

Why indoor air quality matters?

Multifamily buildings provide a great way to house many people in a smaller footprint, but there are some downsides.  Being next to a noisy neighbor is one thing, but having them ruining your indoor air quality is another.  Ventilation in multifamily buildings can be delivered in a couple of different ways. The individual units must be compartmentalized to prevent the sharing of air because shared air also means shared pollutants. This is challenging in multifamily dwellings due to the separation distances for incoming and exhaust air, based on the configuration of dwelling units.

Some of the most common air pollutants found in multifamily and mixed-use buildings are:

  • Smoke
  • Mold
  • Cleaning products
  • Gases released by new furniture or flooring
  • Vehicle exhaust air pollutants
  • Radon
  • Pets
  • Pests
  • Cooking

Some of these pollutants are just irritants but many of these pollutants can lead to short- or long-term health complications.  According to the EPA, poor IAQ often leads to “headaches, allergies, respiratory problems such as asthma, and other serious health problems.”   Most people spend around 90% of their time indoors so the quality of the air they breathe can greatly impact their life, especially since indoor air can be two to five times higher in pollutant concentration than outdoor air.  Specifically with multifamily buildings, one of the hindrances in maintaining IAQ is that pollutants in one unit can travel through ductwork or shared spaces and make their way to another unit.  In other words, the harsh chemicals and odors being used in the apartment or shop downstairs may very well be lowering the IAQ of the apartment upstairs.  The EPA recognizes the importance of improved IAQ and even offers the Indoor airPLUS certification for homes that meet their higher standards.

So pollutants like mold and smoke can travel through the ductwork of HVAC systems but what about viruses like COVID-19?  Droplets and aerosolized particles appear to be the two main pathways for the spread of COVID-19.  While there is still a great deal of debate and research on this topic, what is clear is that aerosolized particles (microscopic infectious particles that an infected person breathes out) can linger in the air sometimes for hours and can be moved around via HVAC systems.  COVID-19 mitigation strategies can be used to limit the impact of HVAC systems on the spread of the disease.  Other diseases such as measles, chickenpox, and influenza have been shown to move around in the same way.

Because pollutants in the air negatively affect people’s health and productivity, governments and municipalities are also starting to enforce codes that ensure everyone has access to better air by outlining much stricter guidelines and requirements for compliance. Many larger cities such as Dallas, Texas even offer an IAQ checklist to help ensure the IAQ of a building can be assessed properly.   Dallas also requires IAQ testing as part of compliance to be a Green Building. Standards that must be followed are typically different for residential and commercial buildings: ASHRAE 62.1 (commercial) and ASHRAE 62.2 (residential spaces) for example.  These standards focus on the same thing, ensuring that occupied spaces will have sufficient IAQ for all occupants by proper filtration and dilution of recirculated air with fresh outdoor air.  Testing, monitoring, and improving IAQ not only ensures that standards are met but also improves occupant health and productivity.

Courtesy: Jordan & Skala Engineers

Courtesy: Jordan & Skala Engineers

What leads to poor indoor air quality?

The IAQ of a building may never be perfect but careful testing, monitoring, and improving can keep IAQ within an acceptable range.  Some causes of reduced IAQ are common such as high carbon dioxide concentrations due to inadequate air ventilation.  Other causes come from how the space is used, such as smoke wafting up from a restaurant kitchen.  Even something as beneficial as hand sanitizers gives off ethanol that negatively affects IAQ.  The first step to improve IAQ is to determine the source of the pollutants.

Manufactured products like new furniture and flooring are often produced using processes that cause them to release volatile organic compounds (VOCs) for quite a while after they are manufactured.  VOCs are chemicals that vaporize easily at room temperature and often lead to noticeable scents such as the “new car” smell.  Some VOCs can be harmful which is why it is good to keep their concentrations in the air low.  If these VOCs are released inside your space, they can negatively affect the building’s overall IAQ.  Two options for managing these issues are purchasing low emission or “green” furniture which are manufactured using materials that give off fewer VOCs or, if possible, baking off many of the VOCs.  To off-gas the VOCs, place the furniture in the space where it will be used and then cycle the temperature in the space.  By heating the space to 80F-85F for 12 hours and then cooling the space down as low as it can reasonably go for the next 12 hours while the space is well ventilated, the furniture will release the VOCs faster.  This cycle can be repeated as many times as desired before the space becomes occupied.

When purchasing low emission materials, the product supplier is often the best source of information on what products are readily available.  The EPA also has an airPLUS program where low emission products that are compliant with their requirements receive an additional label.  While many products may have a “green” or “eco-friendly” label, looking for these specific labels is a good way to know that the material is a low emission version.  Some of the most common certifications to look for are:

  • GREENGUARD
  • Green Seal Certified
  • Green Wise
  • Eco-Certified Composite
  • APA PS1 or PS2
  • HPVA HP-1

Sometimes it’s not what is happening inside a building that leads to poor IAQ, but the quality of the outdoor air being brought in has an effect as well.  If the outdoor air intakes for the building are poorly located, they may be inadvertently sucking in exhaust air from gas flues, bathrooms, dryer vents, or other undesirable locations.  This means the pristine outdoor air that should be improving the IAQ of the space is actually one of the main culprits in lowering it.  Check to make sure that outdoor air intakes and exhaust air outlets are all properly placed and not causing any building air to short circuit.

Building pressure can also cause problems with IAQ.  If the balance between the outdoor airflow rate and the exhaust airflow rate is upset, the building may become slightly pressurized either positively or negatively.  When a building is slightly positively pressured relative to the outdoor air around it, well-conditioned air gently spills out of the building.  When a building is slightly negative to the environment around it, air is pulled into the building sometimes through sanitary drains, exhaust flues, and other systems designed for air to move the opposite way.  Standing water and long-lasting leaks can also cause problems due to the growth of microorganisms.  These microorganisms are considered biological contamination and should be dealt with immediately.  Make sure filters inside air handlers are dry and any water damaged surfaces are cleaned and replaced.

Courtesy: Jordan & Skala Engineers

Courtesy: Jordan & Skala Engineers

How to improve IAQ?

So now we know why IAQ matters and some of the elements that lead to poor IAQ, but how do we fix it?  IAQ can be improved in three general ways: control the source of pollutants, filter out the pollutants, or increase ventilation.

Controlling the source of pollutants is often the best place to start as it can be considerably easier and less expensive, especially when done early on in the building’s life cycle.  IAQ testing can be done to determine what pollutants exist in the air.  If, for example, some of the cleaning agents being used in a space are ruining the IAQ, switching to “green” cleaning products may be all that is required.  If mold is causing the low IAQ, isolating the source and replacing materials may solve the problem.

When pollutants need to be filtered out/removed from the air to improve the IAQ of a space, it’s important that the right method is selected. Some of the most common technologies on the market are:

  • FILTRATION (MERV or HEPA filters)
  • DILUTION (introduction of outside air)
  • REMOVAL/EXHAUST (unit or single-room ventilation)

MERV ratings for a filter describe how efficient a filter can capture particulates in the air.  The higher the MERV rating, the better the filter can capture smaller particulates.  A MERV 8 filter, common in dwelling unit air handlers, is at least 84.9% efficient at stopping particles that range from 3.0 to 10.0 microns whereas a MERV 12 is at least 90% efficient.  The downside of these higher MERV ratings is the increased pressure drop they add to a system, causing the fans to have to work harder.  It is important that the air handler be designed to handle the increased static pressure that higher efficiency filters add to a system.

Every application is different and sometimes filtration just isn’t the answer.  When increased ventilation is the solution, IAQ can be improved by increasing the number of times an hour the air inside a space is changed over.  Replacing “stale” air in a space with fresh outdoor air lowers the concentrations of contaminants in the air, reducing smells and increasing the quality of the air. ASHRAE 62.1 and 62.2 have minimum ventilation rates that are required based on occupancy and how the space will be used.  Although increasing outdoor airflow rates is one of the simplest ways to improve IAQ, it can become expensive quickly.  In their publication on IAQ for Multifamily Building Upgrades, the EPA estimates that 43% of all energy use in the US is used for heating and cooling buildings.  Outdoor air should be properly conditioned before being delivered into a space.

Courtesy: Jordan & Skala Engineers

Courtesy: Jordan & Skala Engineers

One strategy for balanced ventilation for larger shared spaces or common amenity areas is demand control ventilation (DCV).  Demand control ventilation provides a compromise between the cost of increased ventilation and the importance of higher IAQ.  DCV uses the scheduling of the building’s occupancy or sensors in the space to vary the amount of ventilation air introduced to the space.  DCV is implemented by measuring the amount of carbon dioxide introduced into a space, to determine how much outdoor air should be introduced.  As the CO2 in the space increases, the system can introduce more outdoor air to lower the concentration of pollutants.  When the IAQ is sufficient in the space, the amount of outdoor air being brought in can be reduced to save on operating costs.

Because of how complicated IAQ can be, sometimes the best answer is to bring in the professionals that know IAQ inside and out.  The Sustainability team at Jordan & Skala Engineers can provide a holistic approach to energy efficiency and indoor air quality, and work with your mechanical engineers to implement an effective system.  IAQ testing, based on LEED & WELL standards, provides a clear baseline to improve upon.  Measuring outside air delivery ensures that the mechanical systems are functioning as designed and are meeting current standards for ventilation air.  Onsite verification and inspection of units can ensure that duct and unit leakages aren’t wasting money and sacrificing IAQ.  From commissioning to recommending new strategies for outdoor air management, the experts at Jordan & Skala Engineers are ready to help improve your IAQ.

 

This article originially appeared on Jordan & Skala’s websiteJordan & Skala Engineers is a content partner of CFE Media.


Tim Milam, PE
Author Bio: Tim Milam, president, Jordan & Skala Engineers