Part of responsible
homeownership includes, of course, regular home maintenance. And there
are some tasks that, if deferred, can lead to a home system that’s inefficient
and overworked, which can result in problems and expenses. One such task
is changing the filter of the home’s HVAC system. It’s simple and
inexpensive, and taking care of it at least every three months can mean the
difference between optimum comfort and avoidable repairs.
What Can Go Wrong
Most homes have some sort of furnace or heat pump, and many of those homes
(especially newer ones) have combined heating, ventilation and air-conditioning
or HVAC systems. Each type uses some type of air filter or screen to
prevent larger airborne particles (up to 40 microns) from entering the system
and clogging sensitive machinery. A system that has a dirty filter can
suffer from pressure drop, which can lead to reduced air flow, or “blow-out,”
resulting in no air infiltration at all. Any of these conditions can
cause the system to work harder to keep the home warm or cool (depending on the
season and the setting). And any mechanical component that has to work
harder to run efficiently puts undue stress on the whole system, which can lead
to premature failure, resulting in repair or replacement.
Also, a dirty filter that’s exposed to condensation can become damp, which can
lead to mold growth that can be spread throughout the home by the HVAC
system. This can lead to serious health consequences, not to mention a
compromised unit that will likely require servicing and may require
replacement, depending on the severity of the moisture problem.
Types of Filters
Most HVAC and furnace filters are disposable, made of biodegradable paper or similar
media, and shaped in cells, screens or fins designed to trap as much airborne
debris as possible. Filters can typically be purchased in economical
multi-packs, and there are many types that will fit different models of
furnace/HVAC units. It’s important to use the appropriate filter for your
unit; using the wrong filter that doesn’t fit the unit properly can create the
same types of problems as having a dirty filter. Your HVAC installer can
show you where the filter goes and how to remove the old one and install a new
one. Your unit may also have an affixed label with directions for easy
Your HVAC or furnace technician should service your unit once a year.
Because a furnace/HVAC unit contains moving parts, it’s important that belts
are not cracked and dry, ventilation ductwork is not gapped, cracked or rusted,
and components, such as coils and fans, are clog-free and adequately lubricated
for unimpeded operation. This sort of evaluation is best left to the professional,
unless you’ve had the appropriate training.
The filter of the unit, especially if it’s an HVAC unit that will tend to get
nearly year-round use, should be changed by the homeowner at least every three
months, but possibly more often.
Check your filter’s condition and change it once a month if:
- You run your unit six months a year to year-round.
- You have pets. Pet dander can become airborne and
circulate through the home’s ventilation system just as typical household dust
- You have a large family. More activity means more
household dust, dirt and debris.
- You smoke indoors.
- You or someone in your household suffers from allergies or a
- You live in a particularly windy area or experience high winds
for extended periods, especially if there are no nearby shrubs or trees to
provide a natural windbreak.
- You live in an area prone to or having recently experienced any
wildfires. Airborne ash outdoors will eventually find its way indoors.
- You have a fireplace that you occasionally use.
- You live on a working farm or ranch. Dust and dirt that
gets kicked up by outdoor work activity and/or large animals can be pulled into
the home’s ventilation system, especially through open windows.
- You have a large garden. Depending on its size and how
often you work it, tilling soil, planting, pulling weeds, using herbicides and
pesticides, and even watering mean that dirt, chemicals and condensation can be
pulled into your home’s ventilation system.
- There is construction taking place around or near the
home. You may be installing a new roof or a pool, or perhaps a neighbor
is building a home or addition. Even if the activity is only temporary,
dust and debris from worksites adjacent to or near the home can be sucked into
the home’s ventilation system, and this increased activity can tax your HVAC
system.Change the filter
- The filter is damaged. A damaged filter won’t work as
- The filter is damp. A filter affected by moisture intrusion,
system condensation, or even high indoor humidity can quickly become moldy and
spread airborne mold spores throughout the home via the ventilation
- There is evidence of microbial growth or mold on the
filter. Mold spores already infiltrating the home via the
HVAC system are not only bad for the unit itself, but they can
pose a health hazard for the family, ranging from an irritated respiratory
system to a serious allergic reaction. Tips on Changing the
- Turn off the unit before replacing the filter.
- Use the right filter for your unit and make sure it’s not
damaged out of the package.
- Follow the directions for your unit to make sure you’re
installing the filter properly. For example, many filters use different
colors for the front and back (or upstream and downstream flow) so that they’re
not installed backwards.
- Make sure there aren’t any gaps around the filter frame.
If this is the case, you may have the wrong size filter, or the filter itself
may be defective or damaged.
- Use a rag to clean up any residual dust before and after you
replace the filter.
- Securely replace any levers, gaskets and/or seals.
- Turn the unit on and observe it while it’s operating to make
sure the filter stays in place.
- Note the date of filter replacement in a convenient location for
the next time you inspect it. A filter that becomes dirty enough to
change within a short period of time may indicate a problem with the unit or
ventilation system, so monitoring how often the filter requires changing is important
information for your technician to have.Call a technician for
- Your unit fails to turn back on.
- The fan is slow or makes excessive noise, or the fins are bent.
- The coils are excessively dusty or clogged.
- You notice moisture intrusion from an unknown source anywhere in
the system.Homeowners who take
care of the easy task of changing their HVAC filter can help prevent system
downtime and avoidable expenses, as well as keep their families living and
breathing comfortably. Your InterNACHI inspector can provide more useful
tips and reminders during your Annual Home Maintenance Inspection.
Air Quality IssuesIndoor air quality is
generally worse than most people believe, but there are things you can do
Some Quick Facts:
- Indoor air quality can be worse than that of outdoor air.
- Problems can arise from moisture, insects, pets, appliances,
radon, materials used in household products and furnishings, smoke, and other
- Effects range from minor annoyances to major health risks.
- Remedies include ventilation, cleaning, moisture control,
inspections, and following manufacturers' directions when using appliances and
products.Many homes are built
or remodeled more tightly, without regard to the factors that assure fresh and
healthy indoor air circulation. Many homes today also contain furnishings,
appliances and products that can affect indoor air quality.
Signs of indoor air quality problems include:
- unusual and noticeable odors;
- stale or stuffy air and a noticeable lack of air movement;
- dirty or faulty central heating or air-conditioning equipment;
- damaged flue pipes and chimneys;
- unvented combustion air sources for fossil-fuel appliances;
- excessive humidity;
- the presence of molds and mildew;
- adverse health reactions after remodeling,
weatherizing, bringing in new furniture, using household and hobby
- feeling noticeably healthier outside.Common Sources of Air
Poor indoor air quality can arise from many sources. At least some of the
following contaminants can be found in almost any home:
- moisture and biological pollutants, such as molds, mildew, dust
mites, animal dander, and cockroaches;
- high humidity levels, inadequate ventilation, and poorly
maintained humidifiers and air conditioners;
- combustion products, including carbon monoxide from unvented
fossil-fuel space heaters, unvented gas stoves and ovens, and back-drafting
from furnaces and water heaters;
- formaldehyde from durable-press draperies and other textiles,
particleboard products, such as cabinets and furniture framing, and adhesives
used in composite wood furniture and upholstery;
- radon, which is a radioactive gas from the soil and rock
beneath and around the home's foundation, groundwater wells, and some building
- household products, such as paints, solvents, air fresheners,
hobby supplies, dry-cleaned clothing, aerosol sprays, adhesives, and fabric
additives used in carpeting and furniture, which can release volatile organic
- asbestos, which is found in most homes more than 20 years
old. Sources include deteriorating, damaged and disturbed pipe insulation,
fire retardant, acoustical ceiling tiles, and floor tiles;
- lead from lead-based paint dust, which is created when
removing paint by sanding, scraping or burning;
- particulates from dust and pollen, fireplaces, wood stoves,
kerosene heaters, and unvented gas space heaters; and
- tobacco smoke, which produces particulates, combustion products
Tips for Homeowners
• Ask about formaldehyde content before
buying furniture, cabinets and draperies.
• Promptly clean and dry water-damaged
carpet, or remove it altogether.
• Vacuum regularly, especially if you have
pets, and consider using area rugs instead of wall-to-wall carpeting. Rugs are
easier to remove and clean, and the floor underneath can also be easily
• Eliminate unwanted moisture intrusion by
checking for sources (such as holes and cracks in the basement and other areas,
and leaks from appliances), and by using a dehumidifier.
• Open windows and use fans to maintain
fresh air with natural and mechanical air circulation.
• Always open the flue damper before
using the fireplace. This will also prevent carbon-monoxide poisoning.
• If your air conditioner has a water tray,
empty and clean it often during the cooling season.
• If you smoke, smoke outdoors and away
from any windows and doors.
• Use the range vent above your stove
whenever you cook.
• Use the bathroom vent whenever you use
• Don’t leave vehicles or lawn care
equipment running in your garage. Make sure the door leading from the
home to the garage has a door sweep to help keep out vapors.
Vent Maintenance & SafetyHouse
fires caused by dryers are far more common than are generally believed.
According to the National Fire Protection Agency, fires caused by dryers in
2005 were responsible for approximately 13,775 house fires, 418 injuries, 15
deaths, and $196 million in property damage. Most of these incidents occur in
residences and are the result of improper lint cleanup and maintenance.
Fortunately, these fires are very easy to prevent.
Clothes dryers evaporate the water from wet clothing by blowing hot air past
them while they tumble inside a spinning drum. Heat is provided by an electrical
heating element or gas burner. Some heavy garment loads can contain more than a
gallon of water that will become airborne water vapor and leave the dryer and
home through an exhaust duct, more commonly known as the dryer vent.
A vent that exhausts damp air to the home's exterior has a number of
• It should be connected. The connection is
usually behind the dryer but may it be under it. Look carefully to make sure
it’s actually connected.
• It should not be restricted. Dryer vents
are often made from flexible plastic or metal duct, which may be easily kinked
or crushed where they exit the dryer and enter the wall or floor. This is often
a problem since dryers tend to be tucked away into small areas with little room
to work. Vent hardware is available that is designed to turn 90 degrees in a
limited space without restricting the flow of exhaust air. Air flow
restrictions are a potential fire hazard.
• One of the reasons that restrictions pose
a fire hazard is that, along with water vapor evaporated out of wet clothes,
the exhaust stream carries lint – highly flammable particles of clothing made
of cotton, wool and polyester. Lint can accumulate in an exhaust duct, reducing
the dryer’s ability to expel heated water vapor, which then accumulates as heat
energy within the machine. As the dryer overheats, a subsequent mechanical
failure can trigger a spark, which can cause the lint trapped in the dryer vent
to burst into flames. This condition can cause the whole house to catch fire.
Fires generally originate within the dryer but spread by escaping through
the ventilation duct, incinerating trapped lint, and following its path into
the home’s walls.
Problems & Tips
If your dryer vent terminates in the crawlspace or attic, it can deposit
moisture there, which can encourage the growth of mold, wood decay, and other
structural problems. The vent may also terminate just under the attic
ventilators. This is also a defective installation. Make sure your dryer vent
terminates at the exterior and away from any doors and windows so that damp,
exhausted air won’t re-enter the home. Also, the end of the dryer vent should
have a free-moving damper installed to keep out birds and other pests that like
to build nests in this warm environment. If you find a screen, this is a
defective installation because a screen can block lint and other debris,
causing it to accumulate and leading to a house fire. If it’s safety
accessible, make sure your dryer vent is unobstructed and that the damper works