HVAC red flags to watch for when shopping for a home

Key takeaways

• Buyers should check the HVAC system’s age and condition, since older or poorly maintained units can lead to major replacement costs soon after moving in.
• A careful walkthrough — looking for dirt, damage, pests, odd noises, unusual smells and inconsistent temperatures — can reveal hidden problems that signal neglect or expensive repairs ahead.
• Requesting maintenance records and considering a professional inspection helps buyers understand the system’s true condition and avoid unexpected costs, even if inspections add time and expense to the closing process.

The heating, ventilation and air conditioning, or HVAC, of a home is one of the most critical components for ensuring your new home is comfortable, and it pays to make sure it is in tip-top shape.
There are different costs associated with replacing furnaces, air conditioning units and heat pumps, according to the home services marketplace Angi.

Source: Angi

The costs do not include optional items such as installing ductwork, insulation or a new thermostat. It also doesn't include using environmentally friendly power like geothermal or solar units.

Here's what to look for when buying a home to avoid those exorbitant costs.

HVAC units are designed to last for 15 to 20 years. Look for a label on the unit disclosing the manufacturing or installation date, said Eli Zimmer, director of operations for Luxaire HVAC Services in Baldwin, New York.

"If it’s nearing the end of its lifespan, you could be looking at having to put thousands of dollars toward a new system in the near future," he said.

Dirty filters or dusty vents are bad omens, said Bert Miskell, owner of BPM Heating, Cooling & Plumbing in Frederick, Maryland. "If those items haven't been well maintained, it's very unlikely the system itself has been," he said.

When touring a home, take a good look at the unit itself, said Joe Slom, general manager of Wolcott, a Portland, Maine-based home services company.

"Check for signs of neglect, like rust, dents, frayed wiring or excessive dirt and debris around the furnace or outdoor condenser unit. These may indicate that the system hasn’t been well-maintained."

Rodent activity is another sign of a poorly maintained system, according to W.C. Butler Heating & Air Conditioning in Vinton, Virginia. Look for droppings, nests and signs of chewing or scratching. Also, keep an eye out for small holes chewed through walls, floors and HVAC materials, it said.

Don't get tricked into thinking a unit is new, said Jeremy Henley of TheQuickFix, a tech company in Carlsbad, California, that turns home inspection reports into detailed repair quotes.

"Rehabbers will often install a new, state-of-the-art thermostat, which gives you the feeling that the HVAC system is new, but it does not mean they even serviced the unit, and it could be time for a much more expensive upgrade," he said.

"About five minutes with a can of gray spray paint can make that old and tired AC unit ... 'look' new again," he added. "Don't let the $8 repair fool you that it's a new system."

When the unit kicks on, pay attention to two things — smell and sound, said Miskell. Clangs indicate worn or loose components, while musty odors suggest the presence of mold.

Look for buzzing noises, which can be caused by blocked airflow or electrical issues, according to Estes Services, an Atlanta, Georgia-based HVAC company. A squealing noise could be a broken belt or a bad bearing in a fan motor, it said. A screaming noise can indicate high pressure in the unit’s compressor, which is a safety hazard, it said.

A moldy, musty or even a burnt-dust smell can all indicate issues with an HVAC system, said Zimmer.

Pro tip: "You may also notice that the seller is really trying to mask those smells with other smells, so a strong scent throughout the house could be indicative of some kind of problem," he said.

Fluctuating temperatures could mean airflow problems or even an undersized system, said Miskell. Also check if warm air is leaking into the home through attic doors, recessed lights or even ceiling vents, said Benjamin Uscilla, owner of Evergreen Heating & Cooling in Hamden, Connecticut.

"Air leaks make even the best HVAC system work overtime, so stopping air movement is super important," he said. "Even some of the best HVAC units cannot fix a leaky or poorly insulated home."

There are several simple actions that a prospective buyer can do to check for leaks. A visual inspection around outer walls and windows can locate cracks where air leaks in, according to Allstate. Feel for leaks around electrical outlets, dryer vents, attic hatches and outdoor faucets.

Allstate also suggests using a smoke test to detect leaks. Shut off all appliances that can cause an air disturbance and close all windows and doors. Then light a stick of incense and hold it near an area of possible leakage. If the smoke bends or bows, it indicates a leak.

Ask the homeowner for the age of the unit and any maintenance records, said Miskell. "A decade-old system isn't necessarily a deal breaker, but without maintenance records, it's a total gamble whether you'll get another decade or another month out of it before needing a repair of some kind," he said.

There are potential problems with obtaining an inspection of an HVAC system, according to Fleetwell Air Conditioning, Heating and Plumbing based in Tarzana, California.

What could go wrong: An inspection will cost money and raise the price of closing on the home, it said. It may also delay the closing on a house by several days. A thorough system inspection could have a long turnaround time, meaning a buyer waits while it is completed.

Knowing how well an HVAC system functions pays off in the long run. Keeping your eyes open during a showing can keep your pocketbook closed after you buy.

These signs could mean poor maintenance

• Are there dusty coils?
• Are there dusty vents?
• Are the filters dirty?
• Is there no evidence of maintenance records?
• Is there a buildup of ice on the outdoor components?
• Is water leaking from the indoor unit?
• Is there evidence of damage?
• Is the outdoor unit free of debris?
• Are there signs of pest damage?
• Are the vents clean and unobstructed?
• Is the ductwork visible and intact?
• Is it a smart thermostat?
• Does it respond quickly when adjusted?
• How many zones are there, and do the systems and thermostats work in each zone?
• Are there any warranties or service contracts?
• Has the system ever broken down?

Keep an eye out for deceptive signs that a system is new

• Is the thermostat new? It doesn't mean the rest of the unit is.
• Is the outside of the unit painted? That could mean it's a lot older than it looks.

When in doubt, get an inspection

If you're interested in making an offer on the home but spot a potential problem, you might want to get a formal inspection of the system.

The season in which you get the inspection could affect its outcome. A home in a cold winter climate may not reveal how the air conditioning system flows, and likewise for a heating system during the summer. Ask your inspector how they will overcome this issue.

The average cost of a heating and cooling system inspection is $300, according to home services marketplace Angi. An inspector will typically check both inside and outside the unit, according to ARS/Rescue Rooter, a national chain of HVAC service companies. Service includes:

• Checking coolant level and pressure
• Inspecting the electrical system, including wiring, contacts, capacitors and relays
• Inspecting the condenser, outdoor disconnect, fan motor and blades
• Conducting safety and efficiency checks