How Much Space Should I Leave Open Around My Furnace?

November 5, 2019
client examining the product

Natural gas furnaces need sufficient space and airflow to heat right.

Your furnace can overheat if it doesn’t have enough room. It also makes it challenging for our technicians to perform furnace repair.

Routine furnace maintenance is crucial to keep your system operating smoothly. A routinely serviced furnace may work more efficiently, which could reduce your energy bills.

Related: How Does Furnace Maintenance Impact the Energy Efficiency of Your Home?

Maintenance often helps us spot issues before they become expensive. This could help lessen future repair bills and possibly lengthen the life of your furnace.

So how much room should your furnace really have?

How Much Space Does My Furnace Need?

If you’re finishing your basement or sealing off your furnace room, you should consult manufacturer specifications and Franklin & South Indy ordinances for clearance requirements.

As a general rule of thumb, your furnace should be 30 inches away from furnace room walls on all sides. This lets our service professionals to easily replace it.

You also need to check the area has ample airflow and ventilation, especially if you have an outdated furnace with a metal flue.

Related: Furnace Service or Furnace Replacement: What to Consider

This type of furnace draws combustion air from the surrounding location. If there’s not enough air, unsafe gas fumes and poisonous carbon monoxide could back draft into your home.

If your furnace is positioned in a small room with a gas water heater, you may need to add supplemental openings. This could involve a fully louvered door or vents in the walls.

Not sure if your furnace or water heater has adequate ventilation? We can assist you!


You don’t need to think about airflow and ventilation as much if you have a modern, high-efficiency furnace with PVC piping. Your unit uses one pipe as an exhaust vent and the other to pull in air

Keep Combustible Materials Away from Your Furnace

Although furnace rooms are often also used for laundry and storage space, you should keep yours free of clutter that could be fire hazards.

This includes:

  • Clotheslines
  • Cleaning or laundry products
  • Gasoline, paint or paint thinner
  • Rags and papers
  • Wood scraps and sawdust
  • Used filters

If you have a cat, put your litter box elsewhere. Cat urine contains ammonia, which could corrode your furnace’s heat exchanger. Plus, the furnace could spread unpleasant odors around your home.

You should also routinely sweep around your furnace to stop dust from building up.

Related: Is it Time for Furnace Service or Replacement?

Request Expert Furnace Service

Whether you have to have furnace replacement or annual maintenance in Franklin & South Indy, Winters Heating and Cooling can expertly take care of your needs. Our highly trained technicians can work on any furnace model or brand.

Call us at 317-406-5382 or use our online scheduler to get an appointment right away.