Pollen can affect your HVAC, too

Usually by late February In the southern US, the trees are getting ready to “bust out” with all manner of leaves and pollen.  The smart southerner has already been taking over-the-counter antihistamines for weeks for allergy prevention (believe me, after the first year, it’s marked on the calendar!).  But is your HVAC also ready for this drop in air quality?  Let us explain.

Single grains of pollen are microscopic and invisible to the naked eye.  They generally range from 5 microns to 100 microns in size (1 micron (µ) = 0.001 mm).  However, collectively thousands of pollen grains are visible as a fine powder. This powder is generally yellow in color for airborne allergenic pollen. (Pollen allergy: A beginner’s guide with photos)  Pollen is the male reproductive cells of plants, which need to find their way to an appropriate female plant in order to pollinate and make fruit.  Not all trees and plants produce pollen that is carried through the air; some pollen is designed to be carried by insects.  It’s the wind-polinated types that we need to be concerned about, because in general, these plants produce way more pollen–clouds of it–in order that some of it will reach its intended target.  Pines, redwoods, oaks, alder, birch, ash, grass, and ragweed are some other examples of wind-pollinated plants.

People often think that allergy season only starts when they see blooming flowers, but that is not true. Tree pollen often starts early in the spring before we see leaves on the trees or flowers blooming in the ground. Another myth is that just because you don’t have a particular tree, grass, or weed in your yard, that you can’t be allergic to that pollen. Pollen travels by air and some pollens travel for miles! So just because you don’t have that ash tree in your yard doesn’t mean you can’t be exposed it to. The same goes for different types of grass, weeds and molds as well. (What is Pollen? Can I see it?)

People who react to different types of pollen are doing so not because it actually causes disease in their body (like bacteria or viruses do), but because their immune system cannot distinguish between harmless particles like pollen and harmful particles like viruses. The itchy, sneezy, inflammation reaction to pollen is termed hay fever or pollinosis.  If you want to learn more about why your body reacts to pollen and what to do about it, this article is a good place to start. 

We started talking about HVAC systems and their reactions to pollen. How could that be–HVAC systems aren’t alive!  Well, they do pump air around your home and stuff that’s flying through the air–like pollen–will get sucked into them, and cause major problems.  Check out this video of a homeowner’s “nightmare” when cottonwood trees blossom in June and send white fluff all around her Chicago area apartment.  The fluff, which actually doesn’t even have cottonwood pollen in it, can clog up the outdoor condenser part of your air conditioner and even cause the units to die!  Arboretum specialists do not recommend planting cottonwood trees in residential areas because of this “snowy” issue. 

You should be aware of the components of your HVAC in order to know how pollen will affect them.   You can check out our article for more details on specific types of air conditioners, but here’s an overview:

Air conditioners use a refrigerant to absorb or give off heat.  In hot seasons, the refrigerant absorbs heat indoors through an evaporator coil and is pumped to the outdoors to release the heat through a compressor/condenser coil.  Therefore, you need two components to absorb and release the heat: the evaporator coil indoors (housed in an air handler with a fan), and the compressor/condenser coil outdoors (which also has a fan).  Each set of coils need to be clean in order to exchange heat. When the air is laden with pollen, you can already guess what’s going to happen: the air that carries the heat to/from the coils also lays down pollen on the coils!  When the coils get dirty, heat exchange is affected, so much so that you can have mechanical damage to the system.  Inside, if the HVAC filter gets too clogged or, if the pollen gets by the filter onto the coils, you can get frozen coils. (Top 5 Causes of Frozen AC Coils and How to Fix Them)  Outside, pollen on the condenser coils prevents heat from being released, so the refrigerant doesn’t drop in temperature enough before it re-enters your home. This also decreases the AC’s cooling ability, and if this situation continues for too long, it can overheat the compressor in the outdoor unit. That’s really bad news. If your compressor fails, you may need to replace the whole outside unit.   (Dirty Coils: What They Mean)

Since the highest pollen counts are outdoors and there are typically no filters in a condensing unit, you should have your AC serviced yearly, including washing the condenser.  If you are a DIY’er, check out this video and this non-toxic coil cleaner.  If you have extreme pollen or cottonwood trees in your area, you can consider purchasing and installing filter material over/around your condenser like these products , but you’ll want to monitor these filters daily because if they get too clogged, they can also cause damage to the compressor. 

Indoors, your major protection against pollen will include window screens and the HVAC filter.  Window screens?  That’s right–on those balmy “shoulder season” days where you don’t need heating or cooling, and open the window, a LOT of pollen may also be coming in.  You can prevent pollen and dust from coming into your home by installing some window screens like these, which have a tighter weave than normal screens.  

Also, the type of filter matters to protect your indoor air handling unit.  MERV 8 filters provide basic protection by capturing larger pollen and dust mites with 70-85% efficiency, making them suitable for basic filtration needs with replacement needed every 90 days. For enhanced filtration, MERV 11 filters capture fine dust and pet dander with 85-95% efficiency, making them ideal for homes with pets, requiring replacement every 60 days. And if you want maximum protection, MERV 13 filters capture microscopic allergens with over 95% efficiency, making them perfect for severe allergy sufferers, though they need replacement more frequently, every 30-45 days. (How Air Filters Help Get Rid of Seasonal Allergies)  If in doubt about airflow, contact us with the model number of your air handler (the indoor unit) and the size(s) of your return filter(s).  We can do a calculation to make sure that you have enough filter area to bump up filtration to MERV 12 or 13 without overtaxing your system.  We have a great selection of high-quality filters that have activated carbon to filter out VOCs, as well.

Here are some other symptoms of pollen in your HVAC system: (How Spring Pollen Is Causing AC Clogging: What Every Homeowner Should Know)

• When pollen is causing AC clogging, it creates a sticky layer on your outdoor system’s components. This is especially true after rain, when pollen becomes wet and forms a paste-like substance. 

• Check the area around your indoor AC vents. If you see a yellowish dust or film, that’s a clear sign that pollen is causing AC clogging. You might also notice this same dust on your outdoor AC unit.

• Is your AC running but not cooling your home like it should? When pollen is causing AC clogging, your system struggles to maintain the temperature you set. You might notice some rooms feel warmer than others, or your AC runs constantly without reaching the desired temperature.

• Remember that you also have a very important AC filter in…your car.  Your car’s cabin air filter (which is different from the engine air filter) should be replaced at least once a year, or more often if you have allergies or heavy pollen or air pollution in your area.  

We hate to mention this, but…pollen does increase in intensity and duration, year over year! (For more on why this is, and particular allergy “seasons” you can check out our article here).  Your HVAC may not act like it’s affected by these clouds of allergens, but buildup over time reduces its efficiency and longevity, so if you haven’t done it in a few years, show some love and call the HVAC tech for a “spa day” for your AC.

Photo by freestocks on Unsplash