Is It Ok To Have a Furnace in the Crawl Space?

If you are willing to get your furnace out of your way, then the crawl space might seem like the perfect option. Is it possible to put a heating unit in this part of your house?

You can install a furnace in the crawl space, in case you’re able to adhere to certain regulations. The unit should be easily accessible, have at least 6 inches of space in front of the combustion air opening, and you might have to fire-protect the floor above the unit. 

Where Should a Furnace Be Located in a House?

Homeowners usually choose to install their furnaces in a closet, the attic, basement, garage, or utility room.

Gas furnaces, for example, require air circulation, an exhaust vent, and a gas supply. That’s why the exact location of the unit would be based not only on your personal preferences. 

Does a Furnace Need to Be in the Middle of the House?

You can place the furnace practically anywhere you want as long as it is installed correctly.

However, some experts really do recommend placing the unit as close to the center of your home as possible. This will help the system heat your whole house more evenly and effectively – the heat wouldn’t have to travel for too long to reach all the rooms.

Can a Furnace Be Installed in a Crawl Space?

A crawl space can become a great place for your furnace as it is an out-of-the-way location that is able to provide natural ventilation.

However, it is extremely important to refer to the IRCs (International Residential Codes) before installing a furnace in the crawl space as there are quite a few things that you would have to bear in mind.

  • The furnace should be easily accessible. The opening in the foundation shouldn’t be less than 18 inches by 24 inches; the trap door opening shouldn’t be smaller than 22 inches by 30 inches; there should be enough space for the technicians to perform regular maintenance.
  • There should be at least 6 inches of clear space right in front of the combustion air opening of the unit.
  • The floor above the furnace must be fire-protected. However, if this space is not used for storage and there are no electric or fuel-powered appliances, then you are allowed to not fireproof the floor.

Oil Furnace in Crawl Space

Oil and gas furnaces can be installed in the crawl space, but only if all the local codes and regulations will be adhered to.

Bear in mind that an oil-filled unit would require a vent for directing the fumes out of the house and it also needs a source of fresh air.

Read: How To Choose Furnace Filter?

Furnace Pulling Air from Crawl Space

A lot of crawl spaces have a dirt or gravel floor. This, basically, means that the furnace will be pulling in dirty air.

If that is your case, you would have to insulate the space. You can also install a special vapor barrier – it will help prevent dust and moisture. 

Is It Ok To Have a Furnace in the Crawl Space?

You can certainly place a furnace in your crawl space. As long as it’s installed correctly, you are not going to face any major problems.

However, there are still a few important things that you should bear in mind:

  • Your crawl space is, most likely, dark and damp. This may lead to the formation of mold, and your HVAC unit will easily pick up these mold spores and circulate them around the house.
  • It might be a lot more challenging to fix a unit that is located in the crawl space due to limited accessibility.
  • The heating unit can get damaged during a flood. A crawl space that is located below the Base Flood Elevation should have openings that will allow the water to flow out.

Read: Why Furnace Not Responding To Thermostat?

What Kind of Furnace Do I Need for Crawl Space?

Horizontal-flow furnaces are usually the best fit for a crawl space as they can be positioned on the side and they circulate the air in one end and then exhaust it out of the other.

How to Install a Furnace in a Crawl Space?

If you are opting for a gas or oil-filled furnace, you should consider how you are going to allow air to enter the crawl space. After that, the exhaust gases coming out of the unit would have to be pushed outside the house through a chimney.

The chances are high that your crawl space is already sealed up tight (this will help prevent moisture build-up). So, you would have to find a way to maintain a draft at all times, but, at the same time, you shouldn’t depressurize the space.

Want you can do is install a couple of vents (in the ceiling to the 1st floor). In such a way, the air that is required for combustion will be pulled down whenever there is such a need.

Such an option is much better than installing a vent through which outside air can enter the crawl space, as such air is unconditioned.

Tip: you can also use a combustion air supply unit which is, basically, a fan that is going to blow in the air, once the burner turns on. 

Read: Why Furnace Stops Working At Night?

Horizontal Furnace Installation in Crawl Space

Horizontal furnaces are usually installed in really small spaces that can’t really accommodate a more traditional vertical unit. Such furnaces are less energy-efficient but can work in a house with limited space.

In a horizontal unit, the cool air is drawn in from one side and the warm air is expelled from the other side.  

Crawl Space Furnace Dimensions

You can hang the furnace in your crawl space from floor joists or install it on blocks or a pad. Bear in mind that the pad or blocks should provide enough height (to eliminate the potential of water damage).

If you have a horizontal furnace with a width from around 17 to 23 inches, you should remember that the clearance to combustibles should be 1 inch at the top and 30 inches in the front (for service). The size of the vent should be 2-3 inches.

Should I Air Condition My Crawl Space?

You should definitely opt for a conditioned (closed, sealed, etc.) crawl space. 

In such a case, the space should be lined and sealed with a barrier. After that, you would have to add proper insulation and, finally, a heating and cooling system that is going to be pushing the fresh air from your home down to the crawl space.

A conditioned crawl space will:

  • Improve the air quality in your house
  • Reduce the heating and cooling costs
  • Keep the crawl space dry (no more mold-related problems)

Read: Does Furnace Reduce Humidity?

Do I Need a Dehumidifier in My Conditioned Crawl Space?

A dehumidifier is a great way to prevent mold growth in your crawl space.

However, if you have an encapsulated space, a dehumidifier might be completely unnecessary. Properly encapsulated crawl spaces help keep this part of your house nice and dry.

Such spaces are usually kept dry with the help of the ‘supply air’ method – the contractor can cut a hole in the supply plenum to allow conditioned air to blow into the crawl space. 

Can You Put Air Handler in Crawl Space?

You can put the air handler in your crawl space.

However, you would have to make sure that the unit is level, that the condensation is flowing towards the pipes, and that the supports are firm.

Of course, you would have to make sure that there is enough space in front of the air handler so that the HVAC specialist can perform annual check-ups.

Read: Is Furnace Exhaust Dangerous?

What Is Crawl Space Encapsulation?

When experts talk about the encapsulation of a crawl space, they usually mean the addition of a moisture barrier to the floor of the space, as well as the addition of insulated walls, sealed foundation vents, and a dehumidifier

While insulation prevents heat from escaping your house through the crawl space, encapsulation’s main aim is to deal with humid air and ground moisture.

Make sure to get all these issues out of the way before getting the crawl space encapsulated:

  • Mold growth
  • Insufficient drainage around the foundation of your house
  • Back-drafting from any combustion appliances

An encapsulated crawl space will help you protect this part of the house from mold, improve air quality, and avoid future structural damage that the accumulation of moisture can lead to.