Furnaces and Cooling Systems in Southeast Michigan Homes: What Inspectors Check Before the Seasons Change

Southeast Michigan homeowners ask a lot of their HVAC systems. Furnaces run hard from October through April, and central air has to keep up with increasingly humid summers. During a home inspection, the heating and cooling system gets close attention because it's expensive to replace and easy to neglect. Here's what inspectors are actually looking for.

Age and Life Expectancy

Most furnaces in the region last somewhere between 15 and 25 years, depending on maintenance and installation quality. Central air condensers typically have a shorter lifespan, often 12 to 18 years. Inspectors record the manufacture date from the data plate and compare it to typical service life, since a furnace nearing the end of its expected run is a meaningful factor for buyers budgeting for near-term replacement.

Signs of Wear Inspectors Look For

• Rust or staining around the burner compartment or heat exchanger
• Cracked or brittle wiring insulation
• Excessive dust or debris buildup inside the cabinet
• Unusual smells at startup, which can indicate cracked heat exchangers or dirty burners
• Corrosion on the outdoor condenser coil or bent fins restricting airflow

Ductwork and Distribution

A furnace can be in great shape and still leave rooms too cold or too warm if the ductwork isn't distributing air properly. Many older Detroit-area homes have additions, finished basements, or converted attic spaces where ducts were extended without much planning. Inspectors check for disconnected sections, crushed flex duct, and returns that are undersized for the system. Older homes with gravity furnace conversions sometimes still have oversized trunk lines from the original coal or oil setup, which can affect efficiency.

Combustion Safety

For gas furnaces, proper venting matters as much as the equipment itself. Inspectors check that flue pipes have the correct slope and connections, and that there's no visible corrosion or gaps that could allow combustion gases to escape into living space. Homes with newer high-efficiency furnaces alongside older water heaters sometimes have shared venting issues that need a closer look, since mismatched appliances can affect draft.

Thermostats and Controls

Basic function testing is part of every inspection: does the system respond to thermostat calls for heat and cooling, does the blower engage properly, and is there a noticeable temperature differential between supply and return air. Smart thermostats are common now, but inspectors still verify that the underlying system responds correctly regardless of the control interface.

Cooling System Specifics

Central air systems get evaluated differently depending on the season. In cooler months, a full function test may not be possible without risking damage to the compressor, so inspectors note current conditions and recommend follow-up testing when temperatures allow. When testing is possible, they check refrigerant lines for proper insulation, confirm the condenser is level and clear of debris, and look for ice buildup on the evaporator coil, which often points to airflow or refrigerant problems.

Why This Matters for Buyers and Owners

HVAC replacement is one of the bigger expenses a homeowner will face, and it's not always obvious from a quick walkthrough that a system is struggling. A thorough inspection gives buyers a realistic picture of what to expect and gives current owners a useful checkpoint for maintenance planning before the next Michigan winter arrives.

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