Forced Air Furnaces vs. Boilers: Common Defects Found During Home Inspections

At Mook Home Inspections, we often encounter two primary types of heating systems in homes: forced air furnaces and boilers. While both are effective at heating your home, they operate differently and tend to develop their own unique sets of issues. As part of a thorough home inspection, it’s our job to evaluate these systems for safety, performance, and longevity concerns. Here’s a breakdown of how these systems work and the most common defects we find.

🔥 Forced Air Furnaces: How They Work

Forced air furnaces heat air and distribute it throughout the home using ductwork and registers. They can run on natural gas, propane, oil, or electricity. The system typically includes a blower motor, burner or heating element, heat exchanger, and air filter.

🛠 Common Defects Found with Forced Air Furnaces:

1. Dirty or Clogged Air Filters

   
   

   • A neglected air filter restricts airflow, reduces efficiency, and can overheat the furnace.

     
     

2. Cracked Heat Exchanger

   
   

   • A serious defect that can allow carbon monoxide to leak into the living space. This is a major safety hazard and often requires furnace replacement.

   
   

3. Inadequate Return Air

   
   

   • Poor return air design can cause uneven heating and strain the blower motor.

   
   

4. Rust or Corrosion

   
   

   • Internal corrosion can signal long-term neglect or improper venting. Rust on the burner assembly is a red flag.

   
   

5. Improper Venting or Backdrafting

   
   

   • A common safety issue where combustion gases fail to vent properly, risking exposure to carbon monoxide.

   
   

6. No Recent Service

   
   

   • Lack of routine maintenance is one of the biggest contributors to furnace failure.

💧 Boilers: How They Work

Boilers heat water and circulate it through pipes to radiators or baseboards to warm the home. They can use natural gas, oil, or electricity. Unlike forced air systems, boilers do not use ductwork and often provide a more even, radiant heat.

🛠 Common Defects Found with Boilers:

1. Leaking Components

   
   

   • Leaks around the circulator pump, valves, or pipes are common, especially in older systems. Even small leaks can lead to pressure loss and inefficiency.

   
   

2. Corroded Expansion Tanks

   
   

   • The expansion tank helps manage pressure. If it’s waterlogged or rusted, it can cause pressure fluctuations and system strain.

   
   

3. No Bleed Valves or Air in the Lines

   
   

   • Air trapped in the heating pipes can prevent radiators from heating evenly.

   
   

4. Improper or Missing Pressure Relief Valve Discharge Piping

   
   

   • This is a critical safety component. Missing or incorrect piping can result in dangerous pressure build-up.

   
   

5. Obsolete or Outdated Systems

   
   

   • Very old boilers may lack modern safety controls or efficiency features and could be near the end of their service life.

   
   

6. Improperly Sloped Pipes

   
   

   • For gravity or steam systems, incorrect pipe slope can prevent proper water return and result in noisy, inefficient operation.

🏡 Why It Matters

Whether your home has a forced air furnace or a boiler, regular maintenance and professional inspections are essential. Defects in heating systems can lead to reduced efficiency, discomfort, and even health and safety hazards. During a Mook Home Inspection, we assess the condition of your heating system and identify any visible issues to help you make informed decisions.

🧰 What You Can Do

• Schedule annual maintenance with a licensed HVAC technician.

• Change air filters in forced air systems every 1–3 months.

• Check for signs of leaks, corrosion, or strange noises.

• Install carbon monoxide detectors near sleeping areas, especially if your system runs on gas or oil.

If you’re buying, selling, or maintaining a home, let Mook Home Inspections ensure your heating system is in safe, working condition. Contact us today to schedule your professional inspection!