Inspecting a Home’s HVAC System

Close up of a metal fan in motion.

Home inspection courses will fully cover the various elements of HVAC systems.

Your home inspection courses taught you how to inspect an HVAC system, but you have likely learned in your work thus far that there are many variations among the systems in your area.

HVAC — or as the masses know it, heating, ventilation, and air conditioning — are fairly modern inventions in the history of housing.

For most of human history, fire was the only source of heat. Not only was this dangerous, but it was also time-consuming to keep the home fires burning and didn’t work well in large spaces.

Although heating stoves were used with some success for many years, Air Conditioning, Heating & Refrigeration News reports that the first furnace was invented in 1835 in Worcester, Massachusetts. Mass marketing of these systems did not begin until two years later., a website that teaches consumers how to conserve energy in the home, says that furnaces, boilers, and heat pumps are the three most common methods of heating homes in the U.S. today.

The Addition of Air Conditioning

Many of us take air conditioning for granted today, but it did not come into common usage until after World War II. Up until that time, southerners would sit on their porches during a hot spell with a fan in one hand and a glass of iced tea in the other. Neither was that effective at cooling.

A Florida physician invented a rudimentary form of air conditioning in the mid-1800s — a machine that created ice. Other inventors worked on the issue using similar principles, but the nascent air conditioners were too large and too expensive for the typical residence. Window units became available in the 1930s but didn’t become common for another 20 years, due to their high cost.

Today, according to, 87 percent of U.S. homes have air conditioning.

HVAC for Your Health

Together, a home’s heating and air conditioning systems perform a vital function for its occupants. While it’s true that our ancestors lived without them, remember that life expectancy back then was about 40 years. Thus, it’s essential that these systems do the job they are intended to do — keeping homeowners safe and comfortable.

Most ordinary homes have just one heating and cooling unit. But it’s common today in larger homes to have two A/C units or even more. Square footage is the primary consideration when determining the right size A/C unit for a home (though it’s not the only one), and the average single unit isn’t enough to cool many of today’s McMansions.

Two A/C units outside.

Some homes need two or more A/C units.

Ditto for heating units, although it’s rare to have more than one. Rather, technicians usually complete the determination ahead of time and order the proper corresponding size.

However, homeowners can run into trouble when they decide to expand their living space, whether by finishing an attic or a basement or adding on a room. This extra space the units suddenly need to handle can put a strain on equipment, causing premature wear and tear as well as leaving residents chilly.

Locating the System Components

Regardless of how many units there are, as the home inspector, you should be sure to identify them all and determine which areas of the house each serves. Should there be a heating or cooling issue in any particular part of the home, it would be important to know which unit to trace the problem back to.

Units are often located in attics, basements, or crawl spaces. This puts them conveniently out of sight, but it can present a potential problem. Both furnaces and A/C units blow out conditioned air, but they get the air from their surroundings. If these spaces are damp, moldy, dusty, filled with rodent droppings or tainted in any other way, the system blows this contaminated air throughout the house whenever it cycles on.

If the vent system is leaky, this compounds the problem by spreading more unhealthy air and wasting money.

While you are checking the vent system’s airtightness, also make note if you find any asbestos tape used to seal connection points. Asbestos is usually not harmful if it is not disturbed; however, it should still be noted in the event that vents are moved or replaced at any point.

Another issue with the location of a gas-powered furnace in a finished basement is the potential for backdraft. Finished basements are much more airtight than their unfinished counterparts. And in an effort to use every square foot of their home, sometimes homeowners wall up the furnace in a tiny, enclosed space. But gas furnaces need fresh air, and if they don’t get it, dangerous gases could build up in the home.

Man repairing a heater unit.

Check to make sure all wires are securely connected.

A/C Needs Fresh Air Too

When checking the location of the air conditioner, besides noting size, make and model, check its general condition. These units are often outside, and thus may be covered with leaves or other debris. Overgrown brush or weeds can also affect an A/C’s proper operation. The unit should stand free and clear and be relatively clean and free of rust.

Many homes have one filter in the venting system that filters the air when either the heat or A/C is running. These filters should be changed or cleaned periodically. If they are not and dust builds up in them, it can affect both systems’ functionality and even cause a breakdown. A filter thick with dust is a sign the current homeowner has neglected upkeep of the home.

Occasionally, you will find a finished basement or attic that isn’t even hooked up to the HVAC system. The homeowner probably skipped this step as a cost-saving measure. And depending on the climate of the area the home is located in, these spaces can be comfortable for six months of the year or longer.

But what about the months when they’re not comfortable? Those are the times these living spaces aren’t usable. Prospective homeowners deserve to know if this is the case, as they likely expect to be able to use all their rooms throughout the year.

Similarly, try to find out if attic or basement rooms are insulated and if so, what type of insulation has been used. Even with proper HVAC connectivity, a lack of insulation can make some rooms unusable during certain seasons.

Other Checkpoints for HVAC Systems

After you’ve located the units and equipment but before you dive into each separate system, check the thermostat. This should be the only control for both systems. If you notice the thermostat has an “emergency” setting on it, this will alert you to the fact the home has a heat pump.

Use the thermostat to make sure both systems turn off and on properly. After you check this out, turn off the power to both units and manually inspect them, looking for loose wires, worn parts, or any other signs of trouble.

Also, make sure the drain for condensation is working properly and is open and clear. A clog in this line could lead to the unit rusting. Further, mold could grow in an area that’s backed up and perpetually wet.

Note any unusual smells in the area. Even a faint smell of gas could signal a dangerous leak. Also, make note of excessively musty odors. Certainly, basements and crawl spaces are naturally damper than areas above ground, but they should not stay wet or smell moldy.

Another bad odor you might smell around HVAC equipment is that of decomposing rodents. These pests commonly invade homes in inhospitable weather, sometimes taking up residence in a heating unit. The smell might be generated by a single mouse, but it also could be a sign of an infestation.

Also, note what type of fuel the system uses. Natural gas? Propane? Oil? Electricity? If the home has a tank to hold fuel versus a simple connection to the public utility, the tank as well as the lines to and from the home must be checked to be sure they are functioning and not degrading in any way.

Why HVAC Inspection Is Important

Certifying the health of a home’s HVAC is critical for many reasons, the first being the occupants’ safety. But given that, homeowners are next most often concerned about their pocketbooks.

According to, the average cost of a new furnace is $4,228. For those living in more expensive areas, it could be as much as $9,000. The average cost of a new air conditioning unit is $5,365. So if either of these systems are damaged or on their way out, the new homeowners could be hit with astronomical expenses they were not planning on.

When you complete your inspection of a home’s HVAC system, if you find anything questionable, recommend to the potential homeowner that they get an inspection by a local, trusted HVAC company. These experts can certify the safety and functionality of these critical home systems.

When you take ICA’s online home inspection course, we prepare you to inspect HVAC systems and all the functions of a home. Get certified with our home inspection course, and get training in identifying mold, radon and more for free. Enroll now.

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