Furnaces and HVAC Systems in Southeast Michigan Homes: What Inspectors Check Before the Weather Turns

In Southeast Michigan, a furnace isn't a luxury item — it's the difference between a comfortable January and a five-alarm plumbing emergency when pipes freeze. 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 when they open that furnace closet door.

Age Is the First Clue

Most residential furnaces are built to last 15 to 20 years, though plenty of Metro Detroit homes still have units running well past that. Inspectors pull the manufacture date from the data plate (not always the same as the install date) to get a sense of where the equipment sits in its lifespan. An older furnace isn't automatically a defect, but it changes the conversation — buyers should budget for eventual replacement rather than assume decades of trouble-free service.

Common Issues Inspectors Flag

• Rust and corrosion around the burner compartment or heat exchanger, often a sign of moisture intrusion or a venting problem.
• Cracked or separated heat exchangers, which can allow combustion byproducts to mix with household air. This is one of the more serious findings and usually warrants further evaluation by an HVAC technician.
• Dirty or missing filters, which restrict airflow and force the system to work harder than it should.
• Improper venting, especially in older homes where furnaces have been swapped out but the venting wasn't updated to match — a common issue when a high-efficiency furnace is paired with a chimney designed for an older, less efficient unit.
• Short-cycling, where the furnace turns on and off more frequently than normal, often pointing to thermostat, airflow, or component issues.
• No carbon monoxide detectors nearby, which isn't a mechanical defect but is a safety gap inspectors routinely note.

Why Combustion Air Matters

Older homes in Detroit, Dearborn, and other established neighborhoods were often built before modern combustion air requirements were common practice. Furnaces need a reliable air supply to burn fuel safely and completely. In tightly sealed basements or mechanical rooms — especially after energy-efficiency upgrades like added insulation or new windows — that air supply can become restricted. Inspectors look at the room the furnace sits in, not just the unit itself.

Air Conditioning Gets a Look Too

During warmer months, inspectors check the condenser unit for physical damage, proper clearance from siding and landscaping, refrigerant line insulation, and whether the unit is running and cooling appropriately for the outdoor temperature. A mismatched or oversized system, common in homes that have had additions or partial renovations, can also show up as uneven cooling between rooms.

What Homeowners Can Do Between Inspections

• Change filters on a regular schedule — more often if you have pets.
• Have the system professionally serviced annually, ideally before the heating season starts.
• Keep vents and returns unblocked by furniture or storage.
• Install and test carbon monoxide detectors on every level of the home.

A furnace inspection isn't about predicting the exact day a system will fail — it's about giving buyers and owners a realistic picture of what they're working with. In a region where the heating season stretches from October through April, that information is worth having before you're relying on the system to actually perform.

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