HVAC Inspection Checklist: Heating, Cooling, Distribution, and Combustion Safety
HVAC is the most expensive system a buyer is likely to replace in the first five years, and the report needs to give them an age, a condition, and an honest statement of what a visual inspection can establish. This checklist covers operation, distribution, condensate, and the combustion-safety items that matter more than everything else combined.
Who orders this
Every home inspection and every 4-point. Ordered standalone before closing when the system is near end of life, and seasonally by homeowners on maintenance agreements.
System Identification
Age drives nearly every HVAC recommendation. Get it from the data plate, not from the thermostat or the seller.
- System type — split, package, heat pump, mini-split, boiler, furnace, or hydronic
- Fuel or energy source
- Manufacture date from the outdoor unit data plate
- Manufacture date from the air handler or furnace data plate
- Mismatched ages indicating a partial replacement
- Rated capacity in tons or BTU
- Refrigerant type — R-410A, R-32, R-454B, or legacy R-22
- Number of zones and thermostats
- Supplemental or backup heat present
- Whether capacity is plausible for the conditioned square footage
Cooling Operation
Run the system and measure. Do not operate cooling when outdoor temperature is low enough to damage the compressor — note the limitation instead.
- System started at the thermostat and reached operation
- Supply and return air temperatures measured
- Temperature split recorded (commonly 14–22°F on a properly charged system)
- Outdoor ambient temperature noted alongside the split
- Compressor and condenser fan operation
- Condenser coil cleanliness and fin damage
- Unit level, on a sound pad, with adequate clearance
- Refrigerant line insulation present and intact on the suction line
- Oil residue at line set connections suggesting a leak
- Electrical disconnect present within sight of the unit
- Evaporator coil accessible and its condition if visible
- Ice on the line set or coil
Heating Operation and Combustion Safety
The highest-consequence section in the report. Do not disassemble — report evidence and refer for evaluation.
- System started in heating mode and produced heat at the registers
- Supply temperature rise within the range on the data plate
- Burner flame appearance — steady and blue rather than lifting or yellow
- Visible heat exchanger condition where accessible without disassembly
- Evidence of flame rollout, scorching, or soot at the burner compartment
- Vent connector slope, support, and secure connection
- Vent material correct for appliance category
- Backdrafting evidence at the draft hood
- Combustion air openings adequate for a confined space
- Combustible clearances at the appliance and the vent
- Carbon monoxide alarm present in the home
- Gas shutoff present and accessible; sediment trap installed
- Flexible gas connector not passing through walls or floors
- Heat pump auxiliary and emergency heat operation
- Boiler pressure, relief valve, and expansion tank condition
Distribution and Condensate
A well-maintained unit attached to bad ductwork still under-performs, and condensate is the most common cause of water damage from HVAC.
- Air filter location, size, and condition
- Return air adequacy and any obviously undersized returns
- Supply registers present in each conditioned room
- Visible duct damage, disconnections, or crushed flex runs
- Duct insulation in unconditioned space
- Duct sealing at joints — mastic or foil tape rather than cloth duct tape
- Panned joist or building-cavity returns
- Primary condensate drain clear and correctly sloped
- Secondary drain pan installed where the unit sits above finished space
- Float switch or safety cutoff present and functional
- Condensate pump operation where installed
- Condensate termination location
- Thermostat operation and programmable settings
- Registers or returns blocked by furniture or closed by occupants
Most common findings — and why they matter
These come up often enough that it is worth knowing the consequence, not just the observation.
Clogged condensate drain with no float switch
Water backs into the pan, overflows, and destroys the ceiling below. A float switch costs almost nothing and prevents the entire claim.
Cracked or suspected-cracked heat exchanger
A carbon monoxide pathway into the living space. It is the one HVAC finding that justifies recommending the system be shut down until evaluated.
R-22 system still in service
Production and import were phased out, so repairs depend on reclaimed refrigerant at high cost. A leak effectively means replacement.
Undersized or missing return air
Starves the blower, drops the temperature split, and shortens equipment life. Frequently mistaken for a low refrigerant charge.
Disconnected flex duct in the attic or crawlspace
Conditioned air dumped into unconditioned space. Common, invisible from inside the house, and expensive on every utility bill until found.
Frequently asked questions
What is a normal temperature split?
Roughly 14–22°F between return and supply on a properly charged and correctly sized cooling system, though the acceptable range shifts with indoor humidity and outdoor temperature. Always record the ambient conditions alongside the split.
Should I operate the AC in cold weather?
No. Most manufacturers advise against running cooling below roughly 60°F outdoor temperature because oil migration can damage the compressor. Note that the test was not performed and why.
How long does an HVAC system last?
Air conditioners and heat pumps typically 12–18 years, gas furnaces 15–25, and boilers longer. Coastal salt exposure, maintenance history, and correct sizing move these ranges substantially.
Can a home inspector confirm a cracked heat exchanger?
Generally no. Confirming it requires disassembly or a combustion analysis outside a standard visual inspection. Report the evidence you observed — flame disturbance, rollout scorching, soot — and refer to an HVAC contractor.
Turn this checklist into a finished report
Walk the property, photograph what you find, and narrate your observations. FieldScribe analyzes the photos, transcribes the voice notes, and drafts the report in professional language — you review, edit, and export the PDF. First report is $9.99 with no subscription.
Related checklists
This checklist is provided free for professional and personal use. It is a general reference, not a standard of practice — inspection requirements vary by state, jurisdiction, and client agreement, and licensing rules for specialty inspections differ. Verify current requirements with your state board and the relevant standard of practice before relying on it in the field.