The Danger of Floor Furnaces. These old heating systems are still hiding under floors across LA — and most homeowners don’t realize how unsafe they’ve become. In-floor furnaces, as opposed to modern central heating systems, were once a popular way to heat homes. But these old units are now outdated and dangerous to use.
What Are Floor Furnaces?
A gas floor furnace is a self‑contained heater set into the floor, usually in a crawlspace, that burns natural gas to deliver warm air through a large floor grille. They were typically located in a hallway or living room. They did not rely on a fan system and ducts to spread heat through the home. Rather, they rely on natural convection as warm air rises from the grate and cooler air falls back toward the heater. Hence, the area of the home where the furnace was located was always significantly warmer than the individual rooms. These furnaces were made by a wide range of manufacturers, from local to national brands.
Floor furnaces started to be seen in the 1920s and 1930s. In the 1940s, they became the primary way homes were heated throughout Los Angeles. They began to fade in popularity in the 1950s and 1960s. The decline was due to fan-driven central heating could use ductwork to heat individual bedrooms. And more importantly, air conditioning could be added to a central heating system.
Where Are Floor Furnaces Seen?
Nearly every home in the San Fernando Valley built in the 1940s post-WWII housing boom was built with an in-floor furnace. However, nearly all of these furnaces have long since been replaced with central heating because of the desire to add central air conditioning.
However, in western parts of middle and south Los Angeles county, such as Venice, El Segundo, Torrance, Compton, Long Beach, etc, where air conditioning is not always considered a necessity, many active floor furnaces remain.
So What is the Danger?
The primary danger is these furnaces are just old. The average floor furnace is 60-80 years old. Most units we come across have signifiant rust. Because of this rust, the heating chambers are often cracked or rusted through. This allowed carbon monoxide to enter the home. Open flames can also escape the fire box and catch surrounding materials on fire. Another issue is the exhaust pipes of these furnaces were often single wall transite material. These older exhaust pipes can develop hairline cracks and let dangerous carbon monoxide gases into the home.
Outside of the dangers of their age, floor furnaces have always had some built-in dangers. Because they use a metal grate, these grates can become hot. Rugs, furniture, blankets, and kids’ toys being placed on the grates can catch fire. Touching the grate can burn a child or pet.
And by today’s standards, they lack such modern safety features as automatic shut-offs, flame roll-out protection, or sealed combustion chambers. In addition, they are extremely energy inefficient.
Lastly, all the manufacturers of in-floor heating have long since either gone out of business or stopped making parts for these units decades ago. Repairing them is nearly impossible.
What Homebuyers Need to Know
If you’re buying a home with a floor furnace, our basic advice is DO NOT use the floor furnace any longer, and budget for a new heating system.
Even if the seller says they’ve “used it every winter,” the unit’s condition likely does not meet today’s expectations for fire safety, energy efficiency, or carbon-monoxide protection. You should discuss this with your real estate agent. Do not assume the seller will pay for an upgrade. The sales price may or may not have factored this in when the home was put on the market. As inspectors, we can not talk about the financial implications of a floor furnace. We just recommend they be replaced.
Book your home inspection now by calling 818-298-3405 or book online here.