Space heaters either use electricity or gas fuel. The selection of gas space heaters falls into three main categories: vent-free, direct vent, and b-vent. Keep in mind that these heaters are more like a furnace than a fireplace. Whether you prefer vented or vent-free gas heaters, the primary function is efficiency over flame aesthetic, and in some cases, the feature of a visible flame is not available at all.
The heating capacity of a gas space heater is determined by its BTU output. BTU stands for British Thermal Units. So, the higher the BTU rating, the more heat your space heater will provide.
Vent Free Wall Heaters
Avenger 26" vent free blue flame heater
Vent-free wall heaters are the most compact space heaters. They attach to an interior wall of your home and burn gas fuel so efficiently that they don't need a venting system. They come in two categories: blue flame and infrared. Many models offer a separate floor stand in case you do not wish to mount it to the wall.
Without a venting system, the heater relies on oxygen from the room and vents directly into the room. Most manufacturers offer vent-free heaters in 6,000, 10,000, 20,000, and 30,000 BTU ranges.
The 6,000 BTU models are the strongest models that are allowed in a bathroom.
The 10,000 BTU units are sufficient for bedrooms.
The 20,000 and 30,000 BTU options are ideal for larger areas such as living rooms, basements, or enclosed porches.
Blue Flame Space Heater
Blue flame with black background
Blue flame heaters have been around for decades and are capable of heating larger areas. As the name implies, this type of heater uses a burner tube that emits a high-temperature blue flame. This high-temperature flame is 800 degrees hotter than the standard hearth appliance. It burns with almost no odor since the additives in the gas are completely consumed by the high heat.
Blue flame wall heaters operate by heating the air in the room, as opposed to infrared heaters that heat objects in the room, which then give off heat. One drawback to blue flame heaters is that the air in front of the heater can become uncomfortably warm. Some people don't mind the hot spots, but it does create a less even heat. These heaters also lose effectiveness in rooms with high ceilings. The hot air rises to the ceiling, so the heaters must continue to heat more room air to keep the temperature warm.
Infrared Space Heater
Infrared heaters generate heat by releasing infrared rays. They create a flame that emits heat in the low-intensity infrared spectrum. So what are infrared rays?
Abstract color wave with black background
The light that we see is a form of electromagnetic radiation made up of different wavelengths. The shortest wavelength we can see is violet light. After that, the shorter wavelengths become ultraviolet light. Even shorter wavelengths are known as x-rays. On the other end of the spectrum, the waves get progressively longer and slower. The longest wavelength shows up as a red light. Even slower waves are called "infrared". Infrared waves are essentially heat waves.
Infrared heaters rely on long infrared heat waves. These waves are completely safe and also very effective at transferring heat to the room. Unlike a blue flame heater, infrared rays do not heat the air. Instead, they heat the objects in the room and the objects, in turn, emit heat.
The result is a very even heat without pockets of hot air near the heater. Another bonus is that the heat is not affected by air movement, so these heaters work for high ceilings. They also radiate heat farther than blue flame heaters and are more effective in large rooms.
Vent-Free Heater Components and Controls
Here are some of the options available with vent-free gas heater models. These are available for both blue flame and infrared heaters.
Floor Stand - This allows the heater to sit on the floor instead of mounting to the wall. Floor stands are especially useful if you want the ability to move your heater to different locations. You can also use it to conceal a gas line that comes up through the floor.
HearthRite heaters with floor stands
Push-Button Ignitor - Vent-free heaters shut down the pilot light if they detect low oxygen levels. During warmer months when the heater is not in use, the pilot light can be manually shut down. The push-button ignitor provides a convenient way to re-light the pilot light with the push of a button.
Manual or Hydraulic Controls - The simplest models feature an on/off switch for operating the heater. If you want more automation, hydraulic thermostat controls are the way to go. These sense the temperature in the room and cycle the heater on and off to maintain your desired range.
Blower – Both blue flame and infrared heaters offer an accessory blower. The blower helps speeds heating the room. It also helps dissipate the extra hot air that collects around blue flame models. The heaters themselves do not need electrical power, but the blower needs a 120-volt power source.
Is a Vent-Free Gas Space Heater Safe?
This style of heater falls under the same rules as other vent-free heating appliances. If vent-free appliances are allowed in your area, make sure to follow all the guidelines for installation. It is only safe to use vent-free heaters in rooms that meet the required size for the heater you are buying.
Keep in mind that all vent-free appliances are banned in Canada and in some areas in the United States. (You can find more information about the restrictions of vent-free appliances by reading our Buyer's Guide for Ventless Fireplaces.)
Maintaining a Vent Free Gas Heater
Brush on a vacuum hose
Inspect the heater at the beginning of the burn season and vacuum away any dust. Also, check the pilot assembly to see if the air intake holes on the side of the pilot tube are clean. If you have a blower, look to see that it is clean, too.
The vent-free heaters use only room air for combustion. Even the cleanest home has floating dust particles that get drawn into the heater during operation. This makes it especially important to vacuum and remove dust. Most manufacturers also provide instructions for lubricating the blower if necessary.
What Is a Wall Furnace?
Direct vent wall furnace
A direct-vent wall furnace mounts to the wall of the home and function as a direct vent fireplace. The venting system consists of one pipe nestled within a larger pipe. The inner pipe carries exhaust gases outside and the outer pipe draws air in.
Unlike a direct vent fireplace, these heaters use a "straight-through" venting system that comes with the heater. This short, horizontal vent kit means that the heater must be installed on an outside wall of the home.
Empire horizontal direct vent kit for homes with vinyl siding
Direct vent wall furnaces have a completely sealed combustion chamber. A burner heats the air in the combustion chamber. The chamber then heats the surrounding metal cabinet, which radiates heat to the room. While operating, these heaters are almost silent and offer pleasant and comfortable heat.
These heaters are the most efficient type of vented space heater. As long as you have space for the heater to be far enough away from flammable objects, you can use these in almost any room. They also heat more square footage than the vent-free models. You can find direct vent heaters ranging from 10,000 BTUs to 55,000 BTUs. (That's enough to be the sole heat source for a single-story home!)
Types of Direct Vent Wall Furnaces
There are three primary styles of direct-vent furnaces: conventional, high efficiency, and high-efficiency counterflow. They come with varying options to meet your needs.
Conventional Wall Furnace
Empire direct vent furnace
This is the least expensive option and features a simple design that is low maintenance. These are easy to install and work well to add supplemental heat to an enclosed porch or home addition. Most models offer an accessory blower so the heat can be dispersed more effectively.
High-Efficiency Wall Furnace
This type of heater boasts higher efficiency than a conventional direct vent heater. The thermal efficiency of a conventional model is around 55 to 65 percent. These high-efficiency space heaters can exceed 80 percent efficiency!
They do this by adding components that make the heater function more like a central heating furnace. Rather than a large open combustion chamber, this type of wall furnace has a "tunnel" type of chamber that sits under negative pressure. The negative pressure comes from an induction fan. This fan draws oxygen into the chamber, increasing the temperature and enhancing efficiency.
The system also uses a powerful convection fan to distribute heat to the room. Many of these systems use a hot surface or spark ignitor instead of a standing pilot flame. This means quick ignition with no chance of a pilot flame outage.
The main drawback of these high-efficiency direct vent heaters is their added complexity and the need for a 120-volt power supply.
High-Efficiency Counterflow Wall Furnace
These heaters have tall, narrow enclosures that recess into a wall and take up very little space. The term "counterflow" refers to how the unit moves the air. Since hot air rises, the heat tends to form a hot zone near the ceiling. A counterflow furnace pulls air from the ceiling through a register called an airdrop. The air is heated as it is forced downward and then released into the room at floor level. The effect heats the room more evenly and efficiently.
Like all direct vent models, it comes with a horizontal vent kit. It must be installed against an outside wall. Counterflow furnaces come in both standing pilot and electronic ignition models. All of them need 120 volts due to the convection fan.
Control Options for a Direct Vent Wall Furnace
Direct vent wall furnaces have more sophisticated control options than vent-free space heaters. They can connect with a wall thermostat, much like a central heating furnace. This makes for a simple "set it and forget it" operation that many appreciate.
What Is a B-Vent Wall Furnace?
B-vent space heaters are also known as natural vent heaters. They have a combustion chamber that radiates heat to the room. Unlike direct vent furnaces, they are not completely sealed to the room and use a vertical vent pipe.
B-vent heaters draw air from the room itself for combustion and vent the fumes to the outdoors. This makes them less efficient than a direct vent furnace, but they do have some advantages. Because they use a vertical vent pipe, they do not need to be on an exterior wall like a direct vent furnace.
They are also available in high outputs and can serve as a primary heat source for smaller homes. There are several types of b-vent models:
Console or Cabinet-Style Wall Furnace
Empire console heater
These models look similar to conventional direct vent wall furnaces. The general setup is also similar, but they are available in a broader range of BTU outputs. (Ranging from 20,000 to over 70,000 BTUs.) The lower range is suitable for heating a couple of small rooms, while the higher output could heat an entire floor of your home. Many are sold with or offer an accessory blower to circulate heat more effectively.
One unique feature of this category is the option of a visual flame model. The optional log set makes the unit look more like a gas fireplace with a visible flame. This aesthetic feature is especially nice if the heater is in a prominent area of the home.
Conventional Wall Furnace
Sunstar thermostat control vent free infrared propane heater
Used for decades in many smaller homes, this upright furnace offers radiant heating. It can also use a blower to push heat into the home. They are meant to be framed into a wall cavity. These furnaces use a special ovalized vent adapter that allows the b-vent flue to be concealed within the wall. While these units are lower output, they are also relatively low cost.
Counterflow Wall Furnace
Direct vent wall furnace
These furnaces operate like the direct vent counterflow models. The only difference is that they trade the direct vent setup for a b-vent flue. While they do lose efficiency because of this, you can locate them virtually anywhere in the home. They also feature a narrow output flue adapter that allows the vent to be concealed within the wall.
Hundreds of thousands of homes use floor furnaces as their sole heating source. While they are not as modern as some alternatives, they are still a solid choice for replacing an existing floor furnace. They are reliable and much less costly than equipping a home with a central HVAC system. These systems mount into the floor of homes with a conventional foundation. They are usually placed in a central room or hallway for better effectiveness. A high output combustion chamber creates heat that rises naturally from the floor grating.
How Are B-Vent Furnaces Vented?
All b-vent furnaces use an appropriately sized b-vent piping system that carries flue gases to the outdoors. While this b-vent can be routed horizontally for short distances, it must make a vertical turn and terminate above the roofline.
The b-vent termination must follow the standard 3-2-10. This means it must extend 3 feet above the roof on the shortest side. The top of the chimney needs to be 2 feet higher than the highest part of the roof within a radius of 10 feet.
All b-vent models can use a wall thermostat for operation. Both wired and wireless versions are available.
How to Clean a Gas Space Heater
Direct vent and natural vent heaters have removable cabinet fronts and access points. Open these to vacuum and remove any dust. Check pilot and ignition assemblies for dust or corrosion and inspect the combustion chamber for any pinholes or rust. Lastly, remove any dust from the blower fan.
How Does a Space Heater Work?
Gas space heaters operate on either natural gas or propane fuels. Models that use electricity require a 120-volt power supply. Vent-free gas heaters do not need venting, but direct vent and b-vent models need proper venting.
Indoor natural gas flex line
Natural gas is supplied to the home via a local utility company. Depending on where the line needs to go, the cost of running a new line could be expensive. It is usually easier to run gas lines in homes with a conventional foundation than in homes built on a slab. Get quotes for the new gas lines when planning for installation so that you can make the best decision.
Propane is stored in tanks in liquid form. The vast majority of homes use natural gas, but propane space heaters are easily accessible if you do not have access to a natural gas line.
For models that use electricity, a simple 120-volt power supply is all that is required. It is usually inexpensive to install an additional outlet. There may even be an outlet that is already close by, making the addition of another outlet unnecessary.
Vented heaters can be converted from one fuel to the other. Companies like Empire make conversion kits readily available. Make sure the conversion is done properly with all of the right components switched. You can go here to read more about converting from one fuel gas to another.
For safety reasons, do not attempt to convert vent-free heaters. The manufacturer will produce and tag them to use only the fuel they were designed to use. Field conversion can be dangerous, releasing toxic byproducts into the air.
Direct vent space heaters come with their own venting kit that must be routed directly to the outdoors. For b-vent and natural vent models, read the owner's manual to determine the size of the vent pipe that is needed. Plan out the routing of the pipe to see if it is feasible to install the heater in the intended location. Obstacles or offset floors can complicate things, but it is possible to use offsets and small horizontal vent runs while routing the pipe. Keep in mind that b-vent piping typically requires a 1-inch clearance to combustibles, so a 4-inch diameter pipe will actually require a 6-inch space.
Are There Electric Heaters That Heat Whole Rooms?
Infrared electric heaters are more effective at heating large rooms than the typical floor convection models. With both indoor and outdoor options, these make a great choice for customers who prefer electric but need more heat than the standard electric heaters.
What Is an Infrared Electric Heater?
Dimplex wall-mounted infrared heater
Infrared electric heaters are often confused with infrared gas heaters. Both use the same concept to heat a room but differently. Electric versions use a coiled tungsten wire within a glass tube. The wire is heated until it generates infrared heat of medium intensity on the infrared spectrum (a gentle warm red glow less intense than high infrared heat).
As with gas infrared heaters, electric infrared models are unaffected by air movement. They are perfect for outdoor installations because even with a strong breeze, they continue to heat the objects beneath them. Think of how it feels to stand outside on a cool sunny day. While the air itself may be cool, the sun's rays still warm you.
These heaters are available in various voltages and wattages. In residential applications, single-phase power inputs like 120 volts and 240 volts are common. Commercial applications use three-phase power options like 208 volts, 277 volts, and 480 volts. Higher voltage allows for greater efficiency but is not always an option depending on the circuitry in the building.
There are two primary types of infrared electric heaters:
Wall-mounted Electric Heater
Bromic wall heater
This type of heater is ideal for outdoor installations since it allows the heater to be close to the area that needs heating. The heater mounts to the wall with a pair of swivel brackets. When purchasing a wall-mounted heater, study the area that the heater needs to cover when mounted. Realistic expectations of what the heater can do will help you know which model is best.
Ceiling-Mounted Electric Heater
This type of heater works for inside or outside applications and is more subtle than wall mounted heaters. Because they are mounted level with the ceiling, this type of heater can cover larger areas.
Electric Heater Control Options
Built-in electric heaters offer a wealth of control options, ranging from simple to sophisticated. The most basic option is a simple on/off control switch within a standard switch box. Another option is a modulating switch that controls the heater by cycling it on and off to stay within the set temperature range.
Central control boxes can handle the operation and cycling of multiple heaters at once. Finally, some systems allow you to connect the heaters to your home automation system. This allows total remote control from your smartphone or computer.
How to Install an Electric Space Heater
A woman turning off a breaker
Electric heaters offer greater flexibility in hard to reach locations. Hire a licensed electrician to evaluate the circuitry in your home. The primary breaker panel must have space for an additional circuit and be rated to handle the new load.
Many newer homes have a 200 amp main panel that still has space for more circuits. Older homes may require a new subpanel to support the heater, especially if you install more than one.
The electrician will give you a quote for the cost of running the new power supply to the heater. A handy homeowner can install the rest of the heater using the manual instructions.
How to Clean an Electric Space Heater
Electric heaters are relatively low maintenance but still require inspection. Exterior heaters may collect spider webs or dust within the heater housing. Clean the heater using a soft cloth or fiber brush. The stainless housing can be wiped down using a water-based cleaner and soft cotton cloth.
While the tungsten tubes used in these heaters are durable, they do have a service life and will require replacement. You can get them from the manufacturer or retailer where the heater was purchased. When installing the new tube, wear gloves to prevent skin oils from fouling the tube. A buildup of oil can create a hotspot that will result in premature failure.
How Will Your Space Heater Be Shipped?
Small models are compact enough to ship via small parcel. The larger wall furnaces and consoles require shipment via LTL carrier. Always inspect the shipment before signing for it!
Vent-free models up to 20,000 BTU are usually small enough to ship using a small parcel. Small electric models that are less than three feet long can also ship via small parcel. Everything else is typically large enough that it requires LTL carrier shipping to keep everything safe.
The shipping company is no longer liable for any damage after you have signed for the package. Look for any damaged or missing parts before you sign.
Direct vent wall heater
There is more available in the category of space heaters than simply those tiny, oscillating convection blowers. It is even possible to heat large rooms or entire floors in a home.
B-vent and direct vent gas models are the most common way to heat very large spaces. Vent-free gas models have a range of heating capability and work well for a single large room. Even electric heaters have options that allow for more effective heating both indoors and out.
If you have any questions about the different kinds of space heaters, we'd love to help! Simply contact one of our NFI certified specialists and we'll answer your questions.
Vent-free heaters have more difficulty operating at elevations above 4,500 feet. This is due to the decrease in oxygen, combined with the fact that the vent-free heaters have an oxygen deletion sensor that will cause the pilot to drop when oxygen levels are too low. This occurs much more frequently at higher altitudes.
Submitted by:Tyler M. - NFI Master Hearth Professional on January 3, 2022
I have an existing Empire vent free gas heater. The unit is about 20 years old and the pilot light is going out nearly daily. Is this something that can be easily fixed or because of the age of the unit should I just replace it?? Thank you.
That's something that generally can be fixed pretty easily. Your thermocouple is likely not recognizing the pilot flame. You will want to clean the thermocouple with a piece of emery cloth or high grit (1000) sandpaper. This should resolve the issue.
I bought a vent free 18,000 BTU wall heater from home depot and after 3 weeks, I had grey blinds and grey/black walls. Why would there be any sooting? It's a natural gas, vent-free heater in a 4 season room!
Sooting can occur when there is incomplete combustion. You can try checking the gas pressure to the unit or if there is enough fresh air for combustion.
Will the Empire RH 65LP operate at high altitude? My cabin is at 8700 ft.
Thanks for your patience. I've confirmed with the manufacturer that this furnace can indeed be used at your altitude. Because of the altitude, though, de-rating of the unit will be necessary. Empire does make a kit (part number P8644) that would properly derate the furnace for altitudes of 8,000 to 10,000 ft. Please remember that derating this unit for your altitude will decrease the BTU output by about 30%.
Are vent free propane heaters legal in my location; or, do all heaters have to be vented?
I am unaware of your state, Montana, having any ban on ventless hearth systems, but this does not mean that your municipality allows them. I recommend contacting your local code office to confirm that ventless systems are allowed prior to ordering.