What Gets Inspected During an HVAC Evaluation
A thorough HVAC inspection covers four main areas: the heating equipment, the cooling equipment, the distribution system (ductwork), and the controls. Each component has specific checkpoints that reveal its condition and remaining service life.
According to the American Society of Home Inspectors (ASHI), HVAC inspection is a required component of a standard home inspection. However, the depth of evaluation can vary significantly between inspectors.
Heating Equipment
For gas and oil furnaces, inspectors examine the burner assembly, heat exchanger, blower motor, and venting system. The heat exchanger check is particularly important. Cracks in the heat exchanger can allow carbon monoxide to enter the living space. This is a safety issue, not just a maintenance concern.
Electric furnaces and heat pumps get evaluated differently. Inspectors look at heating elements, defrost cycles, and supplemental heat operation. These systems have fewer combustion-related safety concerns but still require careful evaluation of electrical components.
Cooling Equipment
Air conditioning inspection involves both the outdoor condenser unit and the indoor evaporator coil. The condenser gets checked for refrigerant line insulation, contactor condition, capacitor function, and fin damage. Fins that look like someone ran a lawn mower over them restrict airflow and reduce efficiency.
The evaporator coil inspection focuses on the drain pan, condensate line, and coil condition. Mold growth in the drain pan is common in humid climates. It's not a major repair, but it indicates the system hasn't been maintained properly.
Ductwork and Distribution
Duct inspection includes checking for disconnections, crushed sections, and insulation condition. In homes with accessible attic ductwork, inspectors can usually see most of the distribution system. Basement and crawl space ducts get similar attention.
Supply registers and return grilles get checked for airflow. Blocked or closed registers create pressure imbalances that stress the system. I always asked homeowners if certain rooms seemed harder to heat or cool. Their answer often pointed me toward duct problems.
Controls and Thermostats
The thermostat test is straightforward. Set it to heat, verify the furnace fires. Set it to cool, verify the AC engages. But the real check is whether the system cycles properly and shuts off when it should.
Programmable and smart thermostats get inspected for basic function. Whether they're programmed correctly is the homeowner's responsibility, but whether they work is part of the inspection scope.
How Inspectors Determine System Age
Finding the age of HVAC equipment requires reading manufacturer data plates. Every furnace and AC unit has a plate that includes the model number, serial number, and manufacturing date. The format varies by manufacturer.
Some manufacturers encode the date in the serial number. Carrier and Bryant use the first four digits to indicate week and year. Trane uses a letter code. Lennox spells out the month. There are online decoders that make this easier, and most experienced inspectors can read common brands without looking them up.
Why Age Matters (And When It Doesn't)
The U.S. Department of Energy estimates furnace lifespan at 15-20 years and AC lifespan at 15-20 years. Heat pumps typically last 10-15 years due to year-round operation. But these are averages, not guarantees.
I've inspected 25-year-old furnaces that showed minimal wear and 8-year-old units that were falling apart. Maintenance makes the difference. Annual professional servicing, regular filter changes, and prompt repairs extend equipment life significantly.
When evaluating older equipment, I focus on current performance rather than manufacturing date. A well-maintained 18-year-old furnace with clean burners and a solid heat exchanger is a better find than a neglected 10-year-old unit with corrosion and combustion problems.
Reading the Data Plate
The data plate is usually located inside the furnace cabinet or on the side of the AC condenser. Information includes manufacturer, model number, serial number, BTU input and output, and electrical specifications.
Common data plate locations:
- Furnaces: Inside the blower compartment door
- AC condensers: Left or right side panel
- Heat pumps: Same as AC condensers
- Boilers: Front or side panel
If the data plate is missing or illegible, the inspector notes this in the report. Without date confirmation, the system age becomes an estimate based on style, components, and technology.
Common HVAC Issues Found During Inspections
After inspecting several thousand homes, certain HVAC problems appeared repeatedly. Some are minor maintenance items. Others are significant defects that affect home value and safety.
Furnace Issues
Cracked heat exchangers are the most serious furnace finding. The heat exchanger separates combustion gases from household air. Cracks allow carbon monoxide to enter the living space. Replacement typically costs $1,500-3,000 for the part alone, but many technicians recommend full furnace replacement for older units with cracked exchangers.
Other common furnace issues include:
- Dirty or clogged burners affecting combustion efficiency
- Inducer motor problems causing improper venting
- Blower motor bearings wearing out
- Flame sensor fouling leading to ignition failures
- Improper venting or backdrafting concerns
Rust on the exterior cabinet looks bad but usually isn't serious. Rust inside the cabinet, especially around the heat exchanger, is a different story.
Air Conditioning Issues
Refrigerant leaks are the most expensive AC problem. Adding refrigerant treats the symptom, not the cause. Leak repair or coil replacement costs $500-2,500 depending on location and severity.
Condenser coil damage is common and usually caused by debris or hail. Bent fins restrict airflow but can be straightened with a fin comb. Crushed or corroded coils need replacement.
Capacitor failure is the most common service call for AC units. The capacitor helps start the compressor and fan motors. A failing capacitor causes hard starting, intermittent operation, and eventual motor damage. Replacement costs $150-300 and takes about 30 minutes.
Frozen evaporator coils indicate restricted airflow or low refrigerant. Common causes include dirty filters, blocked returns, or refrigerant leaks. The ice itself isn't the problem. What caused it is.
Ductwork Problems
Disconnected ducts waste energy and money. Heated or cooled air gets dumped into the attic or crawl space instead of living areas. Reconnection is usually a simple repair, but the problem often indicates sloppy installation practices throughout the system.
Crushed flex duct restricts airflow. This happens when ducts run across attic framing or when someone steps on them. Restricted airflow makes the system work harder to move air, increasing energy costs and reducing equipment life.
Poor duct insulation in unconditioned spaces causes condensation in summer and heat loss in winter. Uninsulated ducts in a hot attic can raise supply air temperature by 20+ degrees before it reaches the room.
Safety Concerns
Carbon monoxide risks from cracked heat exchangers, improper venting, or backdrafting are the most serious HVAC safety issues. Inspectors test for combustion safety using various methods, though opinions differ on whether carbon monoxide testing should be standard.
Gas leaks at furnace connections or valves require immediate attention. The smell of mercaptan (the additive that makes natural gas detectable) near heating equipment indicates a leak that needs repair before operation.
Electrical hazards include improper wiring, missing covers on electrical panels, and double-tapped breakers serving HVAC equipment. These issues require evaluation by a licensed electrician.
Interpreting HVAC Inspection Findings
Inspection reports describe conditions and defects but don't usually assign dollar values to repairs. Understanding which findings matter most helps prioritize concerns during negotiations.
Critical Safety Issues
Some findings should stop the transaction until resolved:
- Cracked heat exchangers or combustion chamber damage
- Active gas leaks
- Carbon monoxide detection in living spaces
- Improper venting with backdraft potential
- Electrical hazards that create fire risk
These aren't negotiation points. They're deal-breakers that need repair before occupancy. Don't let anyone tell you that a cracked heat exchanger can wait.
Major Repair Items
Major repairs affect home value and warrant negotiation:
- Equipment near end of expected life (15+ years for furnaces and AC)
- Refrigerant leaks requiring coil replacement
- Compressor problems indicating impending failure
- Ductwork needing significant repair or replacement
- Undersized equipment for the home's square footage
Request repair quotes from licensed HVAC contractors. Quotes provide negotiating leverage and help set realistic expectations for upcoming expenses.
Maintenance Items
Some findings are normal maintenance that any homeowner handles:
- Dirty filters (replace every 1-3 months)
- Dirty condenser coils (annual cleaning)
- Minor condensate drain clogs
- Thermostat battery replacement
- Register and grille cleaning
These shouldn't be negotiating points. Every home needs ongoing maintenance, and buyers inherit that responsibility at closing.
Questions to Ask After an HVAC Inspection
Good inspection reports prompt smart questions. Here's what to ask based on common findings.
Questions About Older Equipment
When the system is 15+ years old:
- Does the seller have maintenance records?
- When was the last professional service?
- Has any major component been replaced?
- What's the average monthly utility cost?
Maintenance records don't just indicate system health. They demonstrate care and provide context for equipment condition. A seller with complete service records is signaling something about how they maintained the entire property.
Questions About Specific Defects
When defects appear in the report:
- How much will repair cost? (Get multiple quotes)
- Is repair possible, or is replacement necessary?
- How urgent is the issue?
- Will the seller repair before closing?
- Will the seller provide a credit in lieu of repair?
Sellers often prefer credits over repairs. They avoid managing contractors during the selling process. Buyers benefit from choosing their own contractors and overseeing the work.
Beyond the Standard Inspection: When to Get Specialized Evaluation
Home inspectors are generalists. They evaluate visible and accessible components using normal operating controls. Some situations warrant specialized HVAC evaluation by licensed contractors.
When Specialized Inspection Makes Sense
Consider additional evaluation when:
- The system is 18+ years old and you want a detailed remaining life assessment
- The home inspection identified potential heat exchanger issues
- The system uses older refrigerants that will become unavailable (R-22)
- Utility bills seem unusually high for the home's size
- The home has a complex zoning system or multiple units
Licensed HVAC contractors can perform combustion analysis, refrigerant pressure testing, and detailed component inspection beyond home inspection scope.
What Specialized Evaluation Includes
A full HVAC evaluation by a contractor typically includes:
- Combustion analysis measuring efficiency and safety
- Static pressure testing for airflow problems
- Refrigerant charge verification
- Electrical component testing (capacitors, contactors, relays)
- Detailed heat exchanger inspection with camera
- Written estimate for any needed repairs
Cost ranges from $100-300 depending on system complexity and local rates. For older systems, this investment provides valuable information about remaining useful life and upcoming repair needs.
HVAC Efficiency Ratings Explained
Efficiency ratings affect operating costs for years after purchase. Understanding these numbers helps evaluate whether older equipment makes financial sense.
Furnace Efficiency (AFUE)
Annual Fuel Utilization Efficiency (AFUE) measures how much fuel becomes usable heat. An 80% AFUE furnace converts 80% of fuel to heat; 20% goes up the exhaust. A 95% AFUE unit converts 95% to heat.
Older furnaces (pre-1990) typically range from 60-80% AFUE. Modern mid-efficiency units run 80-83% AFUE. High-efficiency condensing furnaces achieve 90-98% AFUE.
Current federal standards require minimum 80% AFUE for non-weatherized furnaces. The difference between 80% and 95% AFUE is significant over the life of the equipment. In cold climates with high heating costs, the upgrade often pays for itself within 5-7 years.
Air Conditioning Efficiency (SEER and SEER2)
Seasonal Energy Efficiency Ratio measures cooling output divided by energy input. Higher numbers indicate better efficiency. The current federal minimum is 14 SEER for northern states and 15 SEER for southern states.
Older AC units (15+ years) often rate 8-10 SEER. Modern units range from 14-26 SEER. High-efficiency units with variable speed compressors can exceed 20 SEER.
As of 2023, new efficiency standards using SEER2 testing protocols apply to new equipment. SEER2 numbers are roughly 5% lower than SEER for equivalent equipment, which confuses comparisons between old and new units.
Heat Pump Efficiency (HSPF)
Heating Seasonal Performance Factor measures heat pump heating efficiency. Current federal minimum is 8.8 HSPF. High-efficiency heat pumps achieve 10-13 HSPF.
Heat pumps also have SEER ratings for cooling mode. A heat pump with high SEER but low HSPF performs well in summer but struggles in winter. Balanced ratings matter for year-round performance.
Special Considerations for Different System Types
Not all HVAC systems work the same way. Inspection approaches vary based on equipment type.
Boiler and Radiator Systems
Boiler systems heat water or produce steam to distribute heat through radiators, baseboard units, or radiant floor tubing. Inspection focuses on the boiler itself, the distribution piping, and the radiators or convectors.
Common boiler issues include:
- Corrosion on the heat exchanger or shell
- Leaking relief valves
- Expansion tank problems
- Circulator pump failure
- Zone valve issues in multi-zone systems
Boilers can last 20-30 years with proper maintenance. Cast iron boilers often last even longer. Age alone isn't a reliable indicator of remaining life.
Heat Pump Systems
Heat pumps provide both heating and cooling from a single outdoor unit. In heating mode, they extract heat from outdoor air and transfer it inside. This makes them highly efficient in moderate climates but less effective when temperatures drop below freezing.
Heat pump inspection includes all the same checkpoints as AC inspection, plus evaluation of the reversing valve, defrost cycle, and supplemental heat operation. The supplemental heat (usually electric strip heaters) activates when outdoor temperatures drop and the heat pump can't keep up.
Common heat pump issues beyond normal AC problems:
- Reversing valve stuck in one mode
- Defrost cycle not activating properly
- Supplemental heat not engaging when needed
- Icing on outdoor coil during heating season
Ductless Mini-Split Systems
Mini-splits use an outdoor compressor connected to one or more indoor air handlers mounted on walls or ceilings. No ductwork means no duct losses, which improves efficiency.
Inspection focuses on the outdoor unit condition, refrigerant line insulation, and indoor unit mounting and drainage. The wall-mounted indoor units need level installation for proper drainage. A tilted unit can leak condensate onto floors and walls.
Mini-split systems are relatively new in North American residential construction. Many are high-quality Japanese or Korean units that perform well for 15-20 years. Some budget options have shorter lifespans and fewer available parts.
Negotiating HVAC Issues in a Home Purchase
HVAC findings often become negotiating points. Understanding typical costs helps set realistic expectations.
Typical Replacement Costs
Full system replacement costs vary by region, equipment quality, and installation complexity. General ranges for 2024:
- Furnace replacement: $3,000-7,000
- AC replacement: $4,000-8,000
- Furnace and AC together: $6,000-15,000
- Heat pump system: $5,000-12,000
- Boiler replacement: $5,000-15,000
- Ductwork replacement: $3,000-10,000
High-efficiency equipment, difficult installations, and premium brands push toward the higher end. Basic equipment with easy access in moderate climates costs less.
Negotiation Strategies
Three common approaches to HVAC defects:
Seller repairs before closing. The buyer gets fixed equipment but doesn't choose the contractor or oversee the work. Sellers typically hire the cheapest option.
Seller provides closing credit. The buyer receives money to handle repairs independently. This allows contractor choice and work oversight. Credits usually equal repair quotes.
Price reduction. Similar to a credit but affects the loan amount rather than closing costs. May be preferred for larger amounts.
For aging but functional systems, consider requesting a home warranty with HVAC coverage. One-year warranties cost $400-700 and provide some protection against unexpected failure in the first year of ownership.
Maintaining Your HVAC System After Purchase
Once you own the home, proper maintenance extends equipment life and reduces operating costs. Here's what actually matters.
What You Can Do Yourself
Regular homeowner tasks:
- Change filters every 1-3 months (1-inch filters monthly, 4-inch filters quarterly)
- Keep outdoor condenser clear of debris, leaves, and vegetation
- Clean supply and return registers
- Check thermostat batteries annually
- Clear condensate drain line with vinegar annually
- Test heating and cooling before the seasons change
Filter maintenance alone prevents most common HVAC service calls. A clogged filter restricts airflow, freezes AC coils, overheats furnaces, and shortens equipment life.
Annual Professional Maintenance
Schedule professional service twice yearly: heating inspection in fall and cooling inspection in spring. A maintenance visit typically costs $100-200 per system.
Professional maintenance includes:
- Combustion analysis and adjustment (furnaces)
- Heat exchanger inspection
- Electrical connection tightening
- Capacitor testing
- Refrigerant charge verification
- Condenser coil cleaning
- Blower motor lubrication
- Safety device testing
Is annual maintenance worth it? The Department of Energy reports that regular maintenance improves efficiency by up to 15% and can extend equipment life by several years. Most HVAC technicians agree that regular maintenance catches small problems before they become expensive repairs.