Home HVAC systems: Basics, maintenance and pest removal

Reviewed by George Baral

Updated September 11, 2023

We often take for granted the luxury we have been afforded by a heated or cooled home at the touch of a button.

HVAC (heating, ventilation, and air conditioning) systems work around the clock, and because they are usually out of sight, they are out of mind. Unless of course, they quit working and we realize how much we depend on them.

HVAC image

The value of HVAC maintenance

HVAC, which stands for heating, ventilation and air conditioning, is technology that ensures our thermal comfort and indoor air quality. HVAC technology has come a long way in the last 20 years with energy efficiency improvements upwards of 40%!

An HVAC system is an important part of any home, even if it isn’t as decorative as a sofa or as noticeable as a refrigerator. In its character, however, it is more reminiscent of your car: it needs regular maintenance to run smoothly.

By doing preventive maintenance, you won’t have the expense of major repairs or parts replacement. In addition, a well-maintained HVAC system provides good air quality in your home, rather than serving as a breeding ground for mould and bacteria.

If you maintain your HVAC system well, it should last for 10 years or so. An HVAC system that is running well translates to less money spent on electricity, heating, and cooling. Dirty or unmaintained units use 20 percent more energy to run than well-maintained systems.

If you keep your system in good repair, doing regular maintenance in spring and fall, it is also less likely to fail during the peak months of winter or summer when you need it most.

Maintenance tasks

To ensure that your HVAC system runs as well as possible, create a checklist of maintenance tasks that you should do periodically:

Monthly or seasonally

  • Check refrigerant lines.
  • In summer, turn off the water to your furnace humidifier.
  • In the fall, replace the humidifier filter and turn the water back on.


  • Replace the battery in your carbon monoxide detector.
  • Check your air-conditioning outdoor unit to make sure it is on level ground.
  • Ensure that your a/c and heating units are free of leaves, grass and pollen.
  • Use a water/bleach mixture to clear the a/c condensate drain.

Troubleshooting HVAC problems

Before you call a repairman to fix your HVAC system, why not see if you can identify the problem yourself? The fix may be so easy that you’ll be cursing yourself for spending money on repairs unnecessarily. Run through this checklist of items and you may be able to save yourself some money, either by fixing it or by identifying the problem so the repairman’s time isn’t spent doing so.

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HVAC basics

Check the thermostat, power, and fuses

  • Is a battery light indicator flashing? Replace your AA batteries and you’re off to the races.

  • Is the temperature setting turned up high or low enough?

  • Is it set at the correct setting? If you want heat and the switch is set to cool, you won’t get the desired result.

  • Your system may have been turned off without you realizing it. Check the outdoor and indoor components to ensure that they are receiving power.

  • Check fuses or circuit breakers. If the power is on but your unit isn’t receiving any, check to see if the fuse or circuit that controls your system hasn’t blown or tripped.

Poor indoor air quality and your HVAC

Check your filter. If your air filter hasn’t been changed for a while, it isn’t properly filtering particles from your indoor air. This compromises the air quality and allows more dust and allergens to collect. Replace your air filter quarterly.

No air flow

  • Check your filter. A dirty filter may be blocking air from getting through. Replace your air filter quarterly.

  • Check your coil. A dirty evaporator coil may cause ice to form on the coil that restricts airflow. Turn your thermostat off for a few hours and see if the system thaws. If airflow is normal again, that was likely the problem.

The HVAC system won’t shut off

  • Check your thermostat. If the thermostat isn’t signaling to your equipment that it should shut down, the system will continue running. Reset your thermostat to see if it solves the problem. If not, you will need a contractor to replace the thermostat.

  • Installation issues? If the contractor didn’t perform a manual J load calculation when installing the system, it’s possible that it is too small for your home. If any of the components are too small, the system will continue running in a constant effort to bring your home to the right temperature.

Hot air from the A/C or cold air from the furnace

If your unit isn’t treating the air, it could indicate a problem with the coils, the refrigerant or the burner. These ARE NOT do-it-yourself problems. Use the thermostat to turn off the system and call a contractor

Many parts are under warranty, so before you replace them, check to see if you’ll be required to pay or not. If you treat your HVAC system well, it should reward you with longevity.

Prevention: Keep your HVAC insect and pest free

Your home is your castle. Outsiders aren’t allowed unless invited and welcomed—at least, that’s true in most cases.

Unfortunately, pests don’t seem to understand that rule. If only there were pest borders surrounding our homes, manned by agents who had the power to turn away these unwanted guests. Instead, the pests—whether mice, cockroaches or raccoons—show up uninvited and walk right in, despite the fact that they actually belong outdoors.

Your HVAC system is one area that is particularly attractive to outdoor pests. If you discover evidence of these critters in your HVAC system components, you’ll need to take steps to get rid of them and employ prevention measures to ensure they never return.

Invasion! When pests enter your HVAC

Close view of wasps nest built on concerte

Pests find their way into your HVAC system for a variety of reasons. Your system may have components that aren’t in good condition, creating openings for them to enter, for example, or you may live in an area that is subject to certain types of infestations, such as insects if you live near wetlands or raccoons if outdoor trash cans are easily accessible.

Once inside your system, pests can damage the HVAC system itself by nesting; they can use the system as a gateway to your home and additional damage, or they can pose a health hazard. The damage they do can be costly to repair.

Your ductwork is very tempting to rodents and snakes, because it provides them a resting place that’s cool during the summer and warm during the winter. Cockroaches like cool, dark places and can squeeze into small spaces easily.

The heat pump or outdoor components of your system are also places these pests enter when the unit is off. However, once the unit turns on, they quickly die at the hands of motors or wires. Your system’s electrical wiring is a tasty snack that appeals to rats and mice.

Consequences of pests in your HVAC

Man reviews outdoor HVAC system

As noted above, pests that invade your HVAC system are health hazards and can also damage the workings of your system, which can be costly to repair.

While money can solve equipment problems, issues with the air quality in your home can be more dangerous, because there is the potential for long-lasting effects. Your home may have odor problems as a result of pest droppings, debris and carcasses in the system that spread throughout the house.

When you attempt to eradicate these critters, pesticides can hurt the air quality in your home. In addition, they may cause irritation to your nose, eyes, and throat; occasionally, a serious case arises where the pesticide causes damage to the nervous system, liver or kidneys. The chemicals in pesticides may also be carcinogenic, so prolonged exposure isn’t always safe.

A number of pests are considered allergens, so ongoing exposure to them could give rise to allergy symptoms. The impact of their dander or remains on air quality may also aggravate asthma or other respiratory conditions. In addition, if pests block a flue, they can prevent poisonous gases such as carbon monoxide from escaping your home.

Pests can also be threats to neighbors or children. If hornets or wasps decide to nest in your HVAC unit, beware of stings. If rodents settle in, they may bite during their outdoor forays.

Once you realize that there are pests making themselves at home in your HVAC system, call a professional to root them out as quickly as possible.

How to keep pests out of your HVAC system

HVAC system enclosed in a custom wood frame, protected from weather and rodents

You can take steps to keep your home’s HVAC system pest-free. As the saying goes, “An ounce of prevention is worth a pound of cure,” so pest-proof your HVAC components as follows:

  1. Seal your ducts

    Ducts are easy entry points for insects; if the seals are loose or cracked, they can easily wander in. You can use foil tape to eradicate small cracks and sealant to close large holes, or you can turn the job over to a professional.

  2. Install vent and flue covers and screens

    You’ll want to cover all exterior flues, exhaust vents, and intakes so that pests can’t enter your home or decide that your pipes make great nesting spots. The vent covers do double duty by preventing rainwater from getting into the vents; make sure they’re approved vent covers and securely attached so small animals can’t shake them loose. You can also place wire mesh screens over the vents to keep insects out more effectively.

  3. Clear the area

    Deter pests from coming near the outdoor components of your HVAC system by keeping the area clear and clean. Regularly remove vegetation growing around it and clear away any excrement, which can attract vermin. Wash the unit and its surroundings with mild soap and water periodically but be sure to get rid of any standing water nearby.

  4. Change your filters regularly

    In addition, consider spraying the condenser and surrounding area with pest repellant, which is chemical-free and contains scents that animals avoid.

  5. Schedule regular maintenance

    Have a professional check your system regularly to ensure that it’s operating as it should and isn’t harboring any unwanted visitors. Although it’s not unusual for pests to visit an HVAC system, they needn’t be invited to stay. Now depending on where you live in Canada, there are HVAC trends such as the type of system you operate and fuel needs. Below are some interesting HVAC facts including how a heating system works and rebate programs to help you save money while you save energy with an HVAC upgrade.

Final HVAC tips and information you should know

For a quick overview of Home Heating and energy efficient HVAC systems in Canada, check out the infographic below.


Want to learn more? Visit our Home Improvement resource centre for tips and inspiration for your next big home improvement project. Or, get an online quote in under 5 minutes and find out how affordable personalized home insurance can be.

About the expert: George Baral

George Baral has an MBA and a masters' degree in chemistry. He spent almost 35 years inspecting and evaluating heating and air conditioning systems before retiring. He obtained a California general contractor's license to start a company focusing on energy-efficient construction, became certified as a LEED AP and earned a NATE (North American Technical Excellence) certification, which provides advanced training for HVAC technicians.


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