The Asthma and Allergy Foundation of America estimates that more than 100 million people in the U.S. experience allergies each year, and there are many allergy triggers that your HVAC systems can exacerbate. These include dust, dust mites, pet dander, pollen, mold spores, and volatile organic compounds. Let’s explore how your HVAC equipment can have an effect and what you can do about it.
Forced Air
Many HVAC solutions are forced-air systems. They have a blower that draws in inside air and forces it through the system. Forced air doesn’t inherently worsen air quality or trigger allergies. It can make matters worse if there’s already a problem. In a household with good dusting habits, you likely won’t notice any adverse effects. If there are bad habits, on the other hand, forced air can make a big difference. It disturbs the dust, makes more of it airborne, and distributes it throughout the home.
HVAC Filters
Heating and air conditioning systems with forced air will usually have some kind of mechanical filtration. That filtration traps particulate matter to keep the HVAC equipment clean and to minimize the air quality impact. Central systems will typically have a filter at the supply vent. There may be multiple supply vents with filters in larger homes. With some furnaces, the filter is inside the unit itself. Ductless mini splits have a filter inside each indoor air handler.
The industry uses the minimum efficiency reporting value (MERV) to measure filter effectiveness. MERV is a scale that ranges from 1 to 16. The higher the rating, the better the filtration. Most modern residential HVAC systems support up to MERV 13. A MERV-13 filter can trap smaller particles and more particles overall than a lower-rated filter. It’s important not to use a higher MERV rating than your system supports. That will increase air pressure too high, which will impact airflow, decrease efficiency, and increase operating costs. Hospitals have larger HVAC systems that can accommodate MERV 16 filters.
Most households with central systems use discardable filters. You should check those filters once a month and replace them with fresh filters as needed. Mini-splits tend to use washable filters, and they’re an option for central systems. You should check washable filters every two weeks and clean them as needed. Homeowners should also replace them once a year.
Most air conditioning experts don’t generally recommend HVAC filters marketed specifically for allergies. Often, you’re paying for the marketing. MERV 9 provides adequate protection for most allergy sufferers. You’ll want MERV 13 or higher if you have bad allergies or are concerned about wildfires. As mentioned, most modern HVAC systems support up to MERV 13. If you have older equipment, you may find that it only supports up to MERV 8.
Ductwork
Central systems use ductwork to distribute conditioned air throughout a home. Ducts can be problematic on two fronts: air leakage and dust accumulation. Leakage can occur over time due to worn seals and other issues. It can cause you to lose as much as 40% of your conditioned air, which drives up your operating costs. Leakage also potentially introduces pollution. Even with good filter habits, dust will accumulate in your ducts over time. That dust can result in persistent odors and trigger and exacerbate your allergies.
The average household needs duct cleaning every three to five years. The expert recommendation is to schedule a duct inspection every other year. A technician can assess whether you need duct cleaning. Your technician can also identify duct problems that require sealing or other repairs. If your ducts are old or in bad condition, your technician may advise replacing the ducts altogether.
Evaporator Coils
Air conditioners and heat pumps have evaporator coils. These coils cause condensation as the air passes over them. That creates an ideal environment for microbial growth. One of the reasons you need a spring HVAC tune-up every year is to clean that coil. Left uncleaned, that microbial growth can wreak havoc on your respiratory system.
Mechanical Ventilation
The presence of some allergens is often unavoidable. A more pressing issue than their presence is their concentration. At higher concentration levels, there will be greater exposure. The typical HVAC system doesn’t take in outdoor air. For residents with allergies, a whole-house ventilation system operates as needed to ensure an ample supply of fresh air. There are even advanced fans that you can run in winter, such as heat and energy recovery ventilators.
Whole-House Air Purification
While central systems provide some air purification, they’re not air purifiers. They only move as much air as needed to cool or heat the home. In addition, the filter is on the supply side, so there are limits because of static air pressure. If you want whole-home air purification, you can add an in-duct air purifier.
Most in-duct air purifiers provide four or more air changes per hour. They typically have mechanical filtration. That’s possible through either a high-MERV filter or a high-efficiency particulate air (HEPA) filter. HEPA filters are even more effective than a MERV-16 filter. They remove over 99% of all particles.
These systems often have activated carbon as well. Activated carbon is effective for odor control. It also removes gases and chemicals that can trigger allergies and are otherwise bad for your health. You can also add an in-duct ultraviolet (UV) lamp that neutralizes over 99% of bacteria, viruses, and other pathogens.
Humidity Control
All households should strive to maintain a relative humidity (RH) between 30% and 60%. An RH outside that range can irritate and even inflame your respiratory system. That can make you more prone to allergies and worsen symptoms. An RH above 60% also makes a home more prone to mold spores and dust mites.
Air conditioners and heat pumps in cooling mode provide some dehumidification. It’s often enough to achieve comfort, but it won’t offset a problematically high RH. For that, you’ll need a whole-house dehumidifier. It will lower RH by extracting moisture from the air.
Furnaces can cause low RH. That’s because they heat air very quickly. That air can then hold more moisture, which it absorbs from the people and objects in your home. There are bypass humidifiers that can offset this byproduct of running your furnace. If your problems with low RH are more widespread, you can opt for a powered whole-house humidifier instead. Both bypass and powered humidifiers add moisture to the air to increase RH and ease allergy symptoms.
Zoning
Zoning is an HVAC design approach that separates a home into discrete areas. That can help by ensuring that triggers in certain zones, such as kitchens and pet areas, don’t get into the bedrooms.
HVAC System Installation and Service in Raleigh
Dawson's Electric & Air is an cooling and heating company that serves homeowners throughout Raleigh and Fuquay-Varina, NC. Our technicians install many cooling and heating technologies. These include central air conditioners, heat pumps, ductless mini-splits, hybrid heating, and furnaces. If you have questions or want to schedule an appointment, call Dawson's Electric & Air today.
