Infrared Heater Buyer's Guide
There's nothing quite like the pleasant, all-over, open-air warmth you get at the beach or from an infrared heater. Yet, somehow, most of our attempts to keep warm center around trapping ourselves inside boxes of hot air. What if there were a way to break out and have that beach warm sensation wherever and whenever you wanted it? And what if heating outside that box literally helped you breathe easier and use less energy?
Well, that's exactly what Infrared Heaters can help you do. And the reason they can is that they don't bother trying to heat air.
- Infrared heater with heat shield
What are infrared (IR) heaters?
Have you ever stood under the porte-cochere of a luxury hotel in winter without feeling cold? Or, have you been comfortable at an indoor hockey game even though the ice wasn't melting? Then you've experienced the wonder of infrared heaters? Infrared heaters heat venues at field level inside stadium arenas from 170 feet away. These heaters don't heat the air in this space. Plus, they cost less money and take less time to heat. Now, a surge in focus from manufacturers in the last 10-15 years has made it so that you harness this power in about any room you'd like, indoors and out.
- Infrared heater with heat shield
Who will infrared heaters appeal to?
Areas you may have thought of as off-limits or hard to heat are accessible with infrared heaters. Rooms with high ceilings, garages, and other semi-insulated spaces are all great candidates. Likewise, conservatories, four-season rooms, and outdoor spaces are also great.
On the true interior of your building, providing heat only where necessary becomes much more practical. And, it works whether you want a well-executed zone heating or you've always wanted a dedicated space for yoga.
- Infrared heater for a yoga studio
People with allergies or other breathing problems report preferring heat provided by infrared. It's one reason infrared heating is the method of choice for hospitals like the U.S. Veteran's Association Hospitals.
Designers love infrared heaters for the floor plan creativity they allow. And the technology is even growing in popularity with building engineers. They find it a perfect marriage for sustainable HVAC systems powered by renewable energy sources.
Users of infrared heaters tend to notice a few advantages right off the bat. First, well-placed infrared warms people and things in the room directly. A whole room doesn't have to warm up before a person feels comfortable. The heat hits its target almost the moment the heater turns on. It also means that when a door opens or a draft blows through, all the heat isn't "lost." Things return to normal much faster.
Second, warming up doesn't need air circulation, so fewer allergens or irritants linger in the air. This isn't only true of dust and pollen on the surfaces in a room, either. Forced air filters and ducts trap dust over time. So, the less often people use their blowers, the happier their eyes, noses, and throats seem to be.
Third, people in many studies score that heat from the right infrared heater feels better. Done right, infrared heating addresses many of the beach warm comfort factors that can't be reduced to thermostat temperature. In winter, there's less of the dried out feeling that comes from using a furnace. The heating action can be directed to stay in the first 6 to 8 feet of height in the room, where it's actually needed. Plus, one of the most overlooked issues in maintaining body heat can be corrected with the right infrared setup. (We take a look at this in the technical section below.)
- Saving money in a jar
Over the long run, avid and shrewd infrared users end up with more money in their pockets, too. Air acts like a middleman collecting a non-stop energy fee to get heat where you want it. Infrared helps reduce its take. Combining that with zone management has been confirmed by study after study to lower energy consumption, and thus costs. They also have some of the lowest overall lifetime costs of ownership of any type of heating appliance.
Further down the line, there are even health benefits to be had as well. When you heat floors and walls with infrared appliances, you can reduce mold and dust mites.
In the end, infrared heaters may help you get more enjoyment out of the space you're in. Indoors they have the potential to free users from the confines of conventional forced-air heating. And outdoors, they can add up to 100 more usable nights per year to space.
Before You Buy
When you install any major appliance, there are "official" considerations to make before you buy. We'll cover the features of different types of infrared heaters later to help you narrow down the one(s) for you. But this section will cover the regulatory side of deciding what to buy.
Infrared heaters have fewer regulations. But, it's good to know what local building authority restrictions might affect your plans. We'll see later that infrared heaters can run on either gas or electricity. So, before you buy an appliance, you'll want to check possible limitations for your "fuel source."
For instance, if you're planning to install an electric heater, verify amperage and voltage needs for the unit. This might require consulting with your electricity provider and a knowledgeable electrician.
- Electrician hooking up electrical components
If you're planning to run a gas appliance, check with a gas plumber and your local gas provider. Whether you plan to use natural gas or liquid propane, you'll need to provide adequate gas pressure to the unit. You'll also want to estimate the consumption rate.
Plug-in appliances don't typically need any special permitting from a local code office. But, gas appliances may be different. Appliances hardwired for electricity as permanent fixtures may need one, too. Commercial installations often call for special permits. So, check with your local building authority or other authority having jurisdiction (AHJ). Also, check with your AHJ if you're planning to install heaters as part of a renovation or addition.
Local authorities start with national standards, or "codes," as a foundation. They have the right, though, to make changes or adjustments as needed in their areas. Your AHJ always has the final word. What it says, goes. And, what's required can vary quite a bit from place to place. So, there's no getting around checking with your local code office.
Code, Certification, and Listing Agencies
Several agencies publish performance and safety standards for manufacturers to test appliances. If the appliances pass the tests, the testing agency will certify and "list" them. It's important to realize that every appliance is not required to be tested to every standard. Some standards only apply to certain appliance types. And some certifications are even completely voluntary. Marks of certification often provide a sense of confidence about a heater's performance. But, the lack of one doesn't guarantee inferiority.
- Certification standards
That said, when a local AHJ tells you what's allowed, it'll also specify which heaters are allowed. So, we'll go over the ones you're most likely to run into while shopping for a heater.
First are the organizations that come up with the standards. Often, standards agencies will collaborate on a standard. There are product standards and procedural standards. Procedural standards are often called "codes." Product standards differentiate categories of products and specify where they can be installed.
Then you have the testing and listing agencies. These are sometimes called labs. They provide manufacturer-independent testing and verification. When you look at the rating tag, data plate, or installation manual of an appliance, the big seal you see is the mark of the listing agency. This product documentation specifies which code or standard the appliance met.
In some cases, the agency that created the standard is also a testing and listing agency, but not always. Here's a list of the agencies that might have had a hand in determining standards for your future infrared heater:
- NFPA: The National Fire Protection Agency outlines procedural standards to prevent fire hazards.
- ANSI: The American National Standards Institute issues product standards for the commercial sector.
- AHRI: The American Heating and Refrigeration Institute creates guidelines for the heating and cooling industry.
- UL: Underwriters Laboratory issues product standards. The standards apply to a variety of products across many industry segments. It used to be catered to the needs of insurance underwriters needing a way to assess the risks of insuring work and exposition sites. Underwriter's laboratory is also a testing and listing agency.
- CSA Group: The former Canadian Standards Association, this is the primary standards agency in Canada. It's neat because it provides coverage of all the areas NFPA, ANSI, and UL do, but under one umbrella.
- International Electrotechnical Commission: Headquartered in London, the IEC sets international standards. These standards apply to almost all electric appliances. Some examples include power generators, transmission and distribution equipment, home and office equipment, and even batteries.
- Intertek: Intertek is a testing and listing agency. While they don't make standards, they test products for conformance to the standards. The certification mark you're most likely to see for infrared heaters is their ETL mark.
- Standards testing
Some of the actual standards you may run into are below. Local code offices specify product types or procedures using these numbers:
- AHRI 1330: This is a special voluntary standard for gas-fired infrared heaters. It's not a safety standard, but it is one that can help you compare one heater to another. We'll go into more detail about it later.
- NFPA 54 / ANSI Z223.1: This is one of the "joint" standards. Installation of any gas appliance in the U.S. should follow NFPA 54/ ANSI Z223.1. These procedures are often called the National Fuel Gas Codes.
- CSA B149.1: These are the Canadian equivalent of the U.S. National Fuel Gas Codes.
- ANSI / NFPA 70: Another of the joint standards, this forms the National Electrical Code. All electrical installations in the U.S. must follow ANSI / NFPA 70.
- CSA C22.1: This is the Canadian Electrical Code.
- NFPA30A 7.6.6: The National Fire Protection Agency limits the operating temperature of infrared heaters. That is, infrared heaters in motor fuel-dispensing facilities and repair garages must not exceed 750 degrees. It's worth checking with your local AHJ for any other local restrictions on heaters. This is especially true if you're planning to install one in commercial areas where automobile fuel may be present.
- NFPA 88: This National Fire Protection Agency sets out standards specific to installations in parking structures.
- NFPA 409: Installations in aircraft hangars should also comply with this NFPA standard.
- ANSI Z83 / CSA 2: The American National Standards Institute and the CSA Group have defined the following product standards which classify different types of heaters.
- ANSI Z83.20/CSA 2.34: Gas-Fired Low-Intensity Infrared Heaters
- ANSI Z83.19/CSA 2.35: Gas-Fired High-Intensity Infrared Heaters
- ANSI Z83.7/CSA 2.14: Gas-Fired Construction Heaters
- ANSI Z83.26/CSA 2.37: Gas-Fired Patio Heaters
- NFPA/ANSI Z21.11.2: This joint standard is used to regulate residential vent free gas heaters.
- IP: This rating is issued by the IEC and designates what kind of intrusion to its enclosure an electrical appliance protects against. IPX4 indicates an appliance is protected from splashing. IPX5 means it can provide protection from water jets. An IPX6 appliance can withstand stronger jets than those in the IPX5 test. These certifications may or may not appear on outdoor appliances otherwise tested or listed for outdoor use.
While this list isn't exhaustive, it should give you a good sense of what you'll run into with your local code office and product manuals.
It's not guaranteed that a job will be over your head. But not every appliance is designed to be installed by the avid DIYer. Even when you're planning to perform an installation yourself, it's a great idea to know where to get help should you need it. You should also get clear on the extent of service a provider is able to offer.
- Hiring a professional
For design help, many manufacturers and some retailers offer their services. They can help you answer questions about what size heaters you need and where to place them. They may also be able to give you some general technical guidance during installation in a jam. But keep in mind that an over the phone consultant can't take the place of an in-person installer.
Depending on the scope of your project, you may need the services of one or more other types of service professionals. For jobs involving new construction or remodeling, you'll definitely have a general contractor. The more familiar your contractor is with your appliance, the better they can coordinate installation. You'll also want someone knowledgeable about your local jurisdiction's residential or commercial codes.
In a similar vein, you'll want an electrician you hire to be familiar with NFPA 70 and any gas plumber or fitter to be familiar with NFPA ANSI Z223.1.
One last thing to be aware of is that installation may need more than mounting and utility connections. It can be a huge help to have someone experienced with your appliance type on-site to make adjustments or test or fine-tune. While electric appliances tend to be more set and forget, gas appliances sometimes require some TLC.
When looking for professionals, you can start with neighborhood recommendation sites. You may also want to have a look at Thumbtack, Houzz, and HomeAdvisor.
Professional certification agencies can also be a great place to look for competent help.
Infrared heaters are popular additions purchased by homeowners who already have hearth appliances. So, you may have luck finding infrared capable technicians at the National Fireplace Institute (NFI). For gas-fired heaters, look specifically for NFI Gas Specialists or Master Hearth Professionals in your area. NFI trained technicians are especially sensitive to the need to treat each appliance as unique. They will also go beyond just the utility connection to complete the installation. While we can't be there in person, the technicians at eFireplaceStore carry and maintain NFI certified standing.
The American Society of Heating Refrigeration and Air-conditioning Engineers also maintains a listing of certified engineers in your area. AHSRAE professionals have unique in-depth knowledge about the intricacies of comfort heating. In fact, ASHRAE is also a procedural standards agency.
Some electrical appliances indicate they should only be installed by licensed professionals. Check your state's licensing requirements for electricians. Licensed electricians will know the local code requirements for your area, and they'll be able to tell you if your job will need a permit. Licensed electricians also carry the required insurance. They can be indispensable for making sure the wiring in your site or home is adequate for the spread of appliances you plan to install.
As we mentioned above, there's no shortage of manufacturer interest in infrared heating technology. Knowing some of the more well-known brands and industry leaders can be a big help navigating the sea of options. Our list below is not nearly exhaustive and doesn't mean to be a ranking. But it is a great tool to get you familiar with where to start looking for a solution that works for you.
- Shipping packages with drones
- Infratech - Based in California and established in 2000, Infratech specializes in up-market outdoor personal comfort wall- and ceiling-mounted heaters for residential and commercial spaces. Their products are known for enabling modern designers to allow their imaginations to take flight. Infratech's quartz tube, medium-wave, lamp-style heaters can be seen in award-winning architect-designed homes, restaurants like Lemonade at Fashion Island, and Del Frisco's Grille, Wynn Casino & Hotel, the Minnesota Twins stadium, and BC Place arena.
- Bromic - Bromic is also based in California and is a direct competitor to Infratech that leans a bit more commercially. They even have a line of heaters designed specifically for luxury cruise ships and super-yachts. They offer both gas-powered ceramic plaque and electric quartz tube lamp-style heaters. You may have seen them in the MGM Grand Las Vegas, W and Sheraton Hotels and Resorts, and restaurants in international destinations like Sydney, Madrid, London, Los Angeles, Newport Beach, and New York.
- Ducoterra - Energy-conscious, sustainable, residential, and commercial heating has been Ducoterra's focus since 2011. This WA based company is unique in that it publishes quantitative studies and energy savings analyses about their infrared technology similar to those usually only performed by and for firms in the industrial sector. Their far-infrared radiant panels are favorites not only in private residences but also in children's therapy facilities and residential facilities.
- eTherma - Since 1981 eTherma has cultivated its image as a source of natural sun-like heat delivered to homes in style and elegance. Their forward-thinking product offerings include residential electric radiant panels, industrial and commercial overhead indoor and outdoor lamps, frost protection equipment for gutters, satellites, pipes, and roofs, as well as low-temperature floor heating systems. With several international offices, including one in IL, their products are used in the Prater Big Wheel Ferris wheel in Vienna, offices, and apartments throughout London, yoga studios in Australia, and Hohensalzburg Castle in Austria.
- Roberts Gordon - On the east coast in NY, Roberts Gordon has been producing heating solutions since 1960. In addition to residential gas-powered tube heaters for garages, they also make tube heaters for commercial, industrial, institutional, agricultural, and military applications. Museums, poultry barns, indoor tennis courts, and racing tracks, and gymnasiums all use Roberts Gordon heaters. They have been one of the most avid adopters of the new AHRI 1330 standard for radiant efficiency. Their innovative reflector design is capable of delivering some of the highest IR Factor of any low-intensity heater on the market.
- King - If it's electric and has to do with heating, King is probably into it, especially when it comes to heating controls. This WA based manufacturer has been producing a vast array of forced air convective, hydronic convective, and radiant appliances since 1958. Their infrared heater offerings include electric overhead quartz tube lamps for commercial use and metal sheath ceiling cove heaters for residential living areas.
- Detroit Radiant Products Company - Staying at the forefront of developing the field of infrared heating technology and education, Detroit Radiant was the first to develop its own listing agency (CSA) approved testing laboratory and continues to publish some of the most comprehensive information about infrared heating engineering and design. While their offerings mostly serve commercial and industrial needs, they also produce gas-powered ceramic plaque heaters and electric quartz and carbon fiber lamps for residential use.
- Herschel Infrared Heaters - This company is named after William Frederick Herschel, who discovered infrared radiation in 1800. Their mission is to change the way people heat themselves in their spaces. Based in the United Kingdom, Herschel offers electrically powered solutions for residential, commercial, and industrial spaces. They are the proud sponsors of heating the Herschel Museum of Astronomy and have a lineup that includes overhead lamps and workshop heaters, as well as radiant panels and ceramic emitter heaters.
Types of Heaters
Because you're reading this on a fireplace website, you've probably guessed that the infrared heaters we sell keep people warm. But, infrared is such a handy phenomenon! It gets harnessed in such myriad ways that it's easy to get disoriented when you first start searching for the right heater. We think it's worth a moment to briefly outline all the kinds of infrared heaters you might see just to help keep you on track.
- Infratech heating element
An infrared heater will fall into one of three categories based on its use: personal comfort, production process, and therapeutic.
Heaters for personal comfort can be used in central heating, zone heating, or spot heating strategies. Homes and businesses might place them indoors or out. But, they're more widespread indoors in industrial applications, like when they're used in airplane hangars and fire stations.
You might also see infrared heaters for commercial, agricultural, or industrial processes. They're used to produce and heat food. Some are made to keep animals warm in pens or stables. Among the more industrial versions are those used for curing, heat treating, moisture removal, non-contact drying, paint baking, and plastics forming.
- Infrared heaters for sealing car paint
They have a role in healing and relief, too. Some models feature heat therapy, like those in saunas or IR (infrared) cabins. Others are designed for light therapy. There are even special sorts to help pain relief and to speed injury recovery.
How does an infrared heater work?
Infrared heating doesn't work the same way we usually think about heating. It's definitely different from what most of us are used to indoors. So, before we plunge right into infrared heaters and how they work, it'll be helpful to look at infrared and heating first. Then we'll look at the important parts of infrared heater construction. Last, we'll look at how to evaluate how well the infrared heaters perform.
Comfort Heating Basics
If you're most interested in personal comfort, let's start with the basics of comfort heating. Two of the ideas sound the same: heating strategies and heat transfer processes. They're both important. But, even though they're related, they are different. The third idea we'll cover in heating is thermal comfort, which is what allows us to tie everything together later.
A heating strategy refers to the relationship between where appliances are placed, how they're controlled, and what spaces they heat. It's something people plan and execute. The three basic strategies are spot heating, zone heating, and central heating. It's possible a person might be using just one or some combination of the three in the same space or building. In fact, infrared can be used as part of any of the strategies as well.
When spot heating, you only generate heat for the desired section of a room, like a workstation. You'll typically only turn it on when you need it. This is the kind of heating you'd use a space heater for.
A zone might be a single room, a small group of adjacent rooms, or a group of similarly used rooms. Zone heating involves delivering heat to zones as needed or as requested. For instance, kitchens and bathrooms, or laundry rooms and basements, aren't occupied as much as other living spaces. So, they might be grouped as a "zone" and put on a separate thermostat than the rest of a home. This means that zones can be controlled independently of one another.
- Infrared halogen heaters on an umbrella
Central heating is probably the most common in the U.S. In this strategy, heat is generated by the main appliance in a central location and then distributed to the different rooms or areas of a building. The single heat setting at the main appliance usually applies to all delivery areas. But, some sophisticated central systems may provide a level of zone control.
Heat Transfer Processes
A heat transfer process is how heat gets from one object to another. Rather than something people plan or do, it's the naturally occurring physics process that people work with or leverage. There are four ways heat can be transferred: conduction, convection, radiation, and evaporation.
- An infrared heater in an auto shop
Conduction is what happens when you burn yourself on a hot stove. It's the transfer of heat between objects directly touching one another.
Convection is actually a compound thing. It's what happens when conduction and fluid motion get together. When one hot object warms the air (or other fluid) around it, which in turn warms another object it's touching, you have convection. This is how most conventional heating appliances work. Most people are familiar with forced air furnaces and everyday space heaters. But even "radiators," whether oil, steam, or hydronic, are really "convectors." They primarily heat the air around them to heat a room. The fins allow their hot surfaces to be in contact with more air.
Radiation is how heat transfers from one object to another when they aren't touching and when there's nothing between them. Waves of electromagnetic energy radiated from a warmer object to a cooler one right through empty space. This is the heat transfer process infrared heaters take advantage of. This is also why you might hear the terms radiant heater or radiant heating in relation to infrared heaters.
Radiation is how the sun is able to transmit heat to us through outer space. Taking advantage of it here on Earth may sound space-age, and it may be gaining popularity, but it's not new. It's how campfires and warmed rocks kept our ancestors warm. And, if you've ever used a fire back in your fireplace, you were exploiting radiant heat transfer. The ancient Romans kept whole buildings warm with radiant heating using structures called hypocausts. And before them, the Koreans were doing the same with systems known as ondol.
- Example of direct infrared heat
When we use radiant energy for heating, the air isn't greedily the first in line to grab its share. We'll see why later. But for now, what's important is that radiant energy directly heats objects, like people, clothes, walls, and furniture. Once those things are warm, the air will follow due to conduction and convection. If, when it's cold outside, you've ever experienced the greenhouse effect in a room with a large bare window and the heat turned off, you've felt how this works. Radiative heating frees us from depending on warming air. That power is exactly why your face can feel warm on a sunny winter day and how infrared heaters keep people warm in open outdoor areas.
Evaporation is another compound process like convection. It's properly called state change and includes not only evaporation but condensation as well. But since it's a bit involved and plays more of a role in cooling systems than heating, we can skip it here. In short, though, it's the process your body uses to keep you cool by sweating. It's also why you may have heard of Low Heating Value and High Heating Value in reference to solid fuel-burning appliances.
Now, all three heating processes, conduction, convection, and radiation, are always at work in any room or appliance. As you've seen, they can't really happen in isolation from each other. For that reason, appliances are classed by which is the predominant heat transfer method they rely on. For example, for a heating panel to be considered a radiant panel by ASHRAE, more than 50% of its heat energy must be transferred into the room by radiation. Otherwise, it gets classified as a convective appliance.
At this point, we just need one more piece to finish our puzzle of comfort heating.
Even though we tend to equate how we feel in a place with its ambient air temperature, experience tells us comfort is much more complex than that. Think back to our pleasant beach. 80 ℉ there sure feels different than it does in the desert. And that same 80 degrees definitely feels better in the shade than it does out of it. The weather report tries to help us compensate by giving us heat indexes and wind chill factors. But none of that tells us why we feel colder sitting on a wrought iron bench in winter than we do on a wooden one.
- Portable infrared heater
This is where the concept of thermal comfort comes from and why we'll need it later to understand infrared heaters. Remember, they don't heat air!
For now, though, it's enough to know that thermal comfort is just as complex as it seems. To get a feel for how involved it is we can browse the definition ANSI and ASHRAE layout in Standard 55 (Thermal Environmental Conditions for Human Occupancy). It lists the following factors, only some of which can be measured in a practical way:
- Mean radiant temperature (the average surface temperature of the objects in a room)
- Dry bulb temperature (the ambient air temperature we're used to)
- Wet-bulb temperature
- Metabolic rate
- Radiant temperature asymmetry (as when you have a hot face but a cold back)
- Vertical stratification and gradients (as when hot air rises to leave your head warm but your feet cold)
- Floor temperature
Studies identify other factors, too, like a person's health and a thing called acclimatization. This is the big word that explains why 72 ℉ indoors might feel delightful when you come from outdoors in winter but not so much in summer.
There are also some generally accepted well-known causes of thermal discomfort. Too high a dry bulb temperature with too low a mean radiant temperature is a common one. Relative humidity below 50% is another, as is a dew point that's too low or too high. Warm air moving around is one most of us are familiar with.
In the end, the point of thermal comfort is that being comfortably warm is about more than just air temperature. And, though it's not as immediately obvious, it confirms for us something we already know in our gut. Namely, what's most important in comfort heating is what's happening in the lowest 6-8 feet of the room. That's where thermal comfort happens because that's where we are.
With the heating part behind us, we can turn to the infrared part. After we cover infrared energy in general, we'll need to look at how it behaves. Specifically, we'll look at how it's absorbed, how it's emitted, how it's reflected, and a thing called view factor.
When we mentioned waves of electromagnetic energy transferring heat in the previous section, we were actually referring to infrared waves. As one section of the electromagnetic spectrum, it's the same kind of "thing" as visible light. Visible light is not itself color, but color "happens" when it hits an object. Infrared is the same way. It's not itself "heat," but heat happens when objects absorb it. In fact, we section off all the parts of the electromagnetic spectrum by their effects this way.
Below is a list of other sections of the electromagnetic spectrum and what they do. They're listed in order from shortest to longest wavelength:
- Infrared heating technology
- Gamma rays: This is the dangerous "radioactive" radiation from nuclear explosions.
- X-rays: These are exactly what you think they are.
- Ultraviolet: These cause tanning, wrinkles, skin cancer, and eye damage. But they also make things glow (black lights).
- Visible light: Remember Roy G. Biv? (From shortest to longest this would be violet, indigo, blue, green, yellow, orange, red)
- Microwaves: These can also transfer heat but are used for cooking.
- Radio: These, too, are what you think they are. But besides TV and radio signals, they're also behind RADAR (Radio Detection and Ranging).
Infrared falls right between visible light and microwaves on this list. It would be just below red on the way to microwaves, which is why it's called infrared. Even though infrared is the primary energy behind heat transfer by radiation, it isn't harmful in normal circumstances. The one to be concerned about is called "ionizing" radiation, which is the UV through gamma wavelengths.
Except in special circumstances, infrared isn't visible. UV isn't typically visible either. But you've probably heard ultraviolet called UV light. That's partly because it's a close neighbor to visible light. For the same reason, you may come across the term infrared light. Like visible light infrared travels at the speed of light (186,282 miles per second), which for comfort heating applications is instant. And, while we can't normally see with it, all objects, including people, emit some infrared. This is what makes thermal imaging ("Predator-vision," if you remember the movie) possible.
Just as the overall electromagnetic spectrum is broken down into sections, or "bands," by its effects, the infrared band is, too. The nearest neighbor to visible light is called, unsurprisingly, near-infrared. It's also called NIR, short wave infrared or short wave IR and IR-A. Of all the infrared bands, it tends to penetrate the most deeply into human skin and some other materials. This makes it particularly useful in light therapy and in industrial paint curing.
The mid-infrared band (MIR) is also referred to as medium wave infrared and IR-B. For reasons we'll see later, this is a favorite band when a balance between heater distance and comfort is needed.
If you guessed the last band is called far-infrared because it's the farthest from the red light, you're right. It's also called FIR, long-wave infrared, and IR-C. Human skin and water really soak up this band. It's the most comfortable and gentlest-feeling of the three.
Absorptivity, Emissivity, Reflectivity, & View Factor
Absorptivity denotes a material's ability to absorb electromagnetic energy. Every material absorbs some part of the spectrum better than others. For example, we now know that water readily absorbs long-wave infrared. (It also absorbs microwaves very well, which is why microwave cooking is possible.) On the other hand, infrared isn't really absorbed at all by gases whose molecules don't have at least three atoms each.
Since air is mostly nitrogen gas and oxygen gas, which each has only two atoms per molecule, it doesn't really absorb infrared at all. The only exception is the tiny portion of it that is water and carbon dioxide (less than 1%), both of which have three atoms per molecule. This diagram shows what the infrared absorptivity of human skin looks like.
- Infrared heating diagram
Recall that all things emit some infrared. The term used to describe how well a thing emits infrared, or any other radiation for that matter, is emissivity. Just like with absorptivity, which wavelengths and how much of them a substance emits depend on the substance. In general, absorptivity and emissivity are flip sides of a coin. Better absorptivity usually means better emissivity. And if we want to know which bands or wavelengths a material is likely to emit, we can just look at which ones it absorbs.
Another interesting aspect of emissivity is that it increases with a material's temperature. So, the hotter a thing gets the more radiant power it will emit. But that's not all. As a material's temperature rises, the band of radiant energy it emits the most also shifts towards the shorter wavelengths. Remember the list of wavelengths from the previous section. Red wavelengths are closer to the long end of the spectrum, while blue is closer to the short end.
This is why as things get hotter and hotter; they first glow red, then yellow, then blue. Eventually, of course, they end up white, which is what happens when you have all the colors mixed together. Something that hot is probably emitting quite a bit of ultraviolet, which also explains why you don't want to look directly at it.
Putting absorptivity and emissivity together tells us two useful things about infrared heaters. First, the more closely the emitted infrared bands are to the ones the target material absorbs most readily, the better the results we get. Second, to get material to emit shorter bands, we may have to heat it up more, which may cause a brighter glow. The hottest infrared comfort heaters may put out a moderately bright orange glow. For any setting, a heater producer walks a tightrope to balance power output, a ratio of most useful bands, device temperature, and brightness.
A substance might also reflect electromagnetic energy. Reflectivity is much like the other two properties we've discussed. Most materials reflect some part of the electromagnetic spectrum and reflect others. Some bands are fully reflected; others, only partially. As you might assume, a thing's absorptivity is lower the higher its reflectivity is. Shiny metals and mirror-like surfaces reflect the most infrared.
Energy radiates from a source in straight lines perpendicular to the source's surface. Those straight lines form a pattern determined by the shape of the source, just like the visible light from a flashlight, light bulb, or a lamp. This becomes important for two reasons. First, energy only transfers from a source to another object where that object is illuminated by that pattern's shape. Second, the intensity of the power the object receives from a source decreases the further the object is from the source. That pattern, both its shape and the distribution of energy in that shape, determine a source's view factor.
Now that we've covered the basics of infrared and comfort heating, we look at how all this comes together in actual appliances. We'll start with the basic components of infrared heaters and then take a look at how we can evaluate their performance.
- Bromic infrared heating element
Infrared Heater Parts
The common parts of infrared heaters mirror the concepts we discussed in the previous section. That is, every infrared heater is composed of an emitter, a heat source, and a reflector working together to produce a desirable view factor of a preferred absorption range.
As its name suggests, the emitter is the part of the heater that emits the infrared. Two major factors influence the choice of an emitter's material. One is the material's emissivity of the desired infrared band at the appliance's operating temperature. Remember, a heater is most effective when its emission spectrum closely matches the absorption spectrum of its target. The other is the overall radiant power output. A hotter emitter gives off more overall radiant power, which is important because power decreases with distance.
An emitter must be heated by a heating element, which may be a separate part or somewhat integrated. Because the emitter absorbs heat from its source and then re-radiates that energy as infrared, it may be called a heat exchanger in some applications.
In general, hotter materials give off a higher percentage of their infrared in the shorter wavelengths, which are closer to visible light. This requires the hottest heating elements. The hottest ones create view factors with the most radiant power. This makes them great for projecting heat from a longer distance.
But it may also make them uncomfortable if they are placed too close to occupants. This is where heaters with this kind of emitter get the label "high-intensity." The hottest ones also produce the brightest glow, which may be undesirable in some settings. Unwanted light from an infrared heater is called glare.
There are some emitters, though, which produce little or no glare at all. They give off the longest infrared wavelengths and tend to operate at lower temperatures. Heaters with this type of emitter are the most comfortable to be near and may be labeled "low-intensity."
The most common-emitter styles are metal tubes, quartz tubes, quartz bulbs, plaques, flat panels, and metal sheaths.
- Tubal heating element
Metal tubes are several inches in diameter and aren't heated high enough to produce a glow. They may be straight or u-shaped. And, in large custom systems, they may even be serpentine. Black painted stainless steel is a popular material for tube emitters.
Silica quartz glass shaped into a narrow tube-like fluorescent office light is also an effective emitter. The glass itself is clear but may feature coatings for improved performance. Some quartz tubes have a reflective coating, like gold, on one side to improve their view factors. Others have a coating to reduce unwanted glare from the filament inside. They may even be filled with a noble gas still further performance gains. Filling a tube with halogen, for instance, extends the life of a tungsten filament.
The same quartz glass can also be fashioned into a more traditional bulb shape. Quartz bulbs are typically filled with a noble gas as well.
A flat plate with small perforations to allow tiny gas flames to spread evenly over its surface is called a plaque. Plaques are generally either made of metal or ceramic. The ceramic ones tend to give off an orange glow when heated. When plaques are thin enough to be malleable, they may be called "mesh." These allow emitters to be provided in custom shapes.
An emitter may also be shaped as a solid flat panel. Ceramic, sheet steel, and glass are popular materials for this type. Panel emitters have the advantage of a wide uniform view factor. They also aren't heated hot enough to glow. This combination makes them popular choices for living spaces.
Metal might be shaped into a very small diameter tube, similar to a quartz tube, and used as an emitter. To keep them separate from their large metal tube cousins, these skinnier tubes are called metal sheaths.
There are even some methods of using the surfaces of a room – like the ceiling, the floor, and the walls – as emitters. But since these are systems integrated into a building rather than individual heaters, they're best covered in another article.
An emitter must be heated to emit the desired infrared energy. The part of a heater that does this is the heat source.
An electrical resistance filament is used to heat quartz tubes, quartz bulbs, metal sheaths, and flat panels. Some heating element materials you may run into are tungsten, nichrome, FeCrAl alloy (also known as Kanthal), and carbon fiber. Factors that decide the use of one material over another include how quickly a filament heats up or cools down, the preferred band of infrared, the temperature, and the desired radiant power output.
- Bromic ceiling-mounted heater
Filaments may also be snaked throughout and integrated into flat panels. While the filaments used in flat panels aren't heated hot enough to glow, those used in quart tubes and bulbs are. The brightness and color of the glow is a function of temperature. And while some models try to suppress unwanted glare, others may take advantage of the glow to use supplemental lighting.
A gas flame may also supply an emitter's heat. There are both natural gas and propane models of heaters. A flame is used to heat metal tubes, but not metal sheaths. Some larger systems use fans to distribute a vortex-shaped flame down the tube. When the flame is pushed down the tube, the system is called a positive pressure system. Those with the flame pulled down the tube are called negative pressure systems. A gas flame may also be spread over the face of a metal or ceramic plaque. In either case, the flame is provided by a gas valve and burner similar to those on other fireplaces and heating appliances.
Not all the infrared leaving an emitter starts off traveling in the desired direction. But errant infrared can be redirected into a preferred view factor by using one or more reflectors. They're made from materials that have high infrared reflectivity. So, any infrared they absorb is small or even negligible.
Aluminum with a highly polished surface is frequently used. But there can be other reasons a heater may employ a different metal. Some high-end productions even use gold or thin gold coatings to make or enhance reflectors. The best reflectors are carefully shaped to obtain the best view factors for a setting. They may also be used on the non-business side of a flat panel emitter to maximize the infrared emitted into the room rather than the surface it's suspended from.
Infrared Heater Performance
Now that we understand how these heaters work, the next thing we'll want to know is how to tell how well they work. In other words, we're looking for a way to understand heater performance. The bad news is there is no standardized way to compare heaters yet. This is the case whether we want to compare one infrared heater to another or whether we want to compare an infrared heater to a convection heater.
- Heating area of infrared heater
Believe it or not, the U.S. infrared industry has been trying to come up with a standard for the last 30 years. But, it's proven difficult. Describing the way radiation works requires a lot of complex physics and calculus, which we've avoided here. As we'll see later, even though there is currently one standardized metric for infrared heaters, it can't be considered "universal." We aren't completely in the dark though.
The lack of a universal standard for comparison has not stopped manufacturers of infrared comfort heating appliances from promoting a plethora of numbers suggesting the superiority of their models. So, in this section, we'll look at where the metrics we do have come from and what we can do to understand infrared heater performance based on the available information.
Where The Numbers Come From
The numbers we have about infrared heater performance mostly come from two sources: independent manufacturer case studies and individual manufacturer laboratory research.
Many independent studies claim to demonstrate the energy efficiency superiority of infrared heaters over their convection counterparts. To be sure, there have been some ASHRAE and AHRI agency certified studies. But, most of the cost-saving numbers you're likely to see were generated as part of individual manufacturers' customer case studies. A study like this tracks what a customer paid for energy before and after installing that manufacturer's radiant system.
An installed radiant system is likely composed of several individual infrared appliances and was designed specifically for that customer's building. While these studies give us some idea about the relative performance of infrared heaters, they don't help us make direct comparisons.
The other place numbers come from is the laboratory tests manufacturers perform when trying to design heater systems. Most of these tests are done to design a heater with optimal performance parameters for a specific manufacturing process. But some are conducted by manufacturers of comfort heating and therapeutic appliances as well. These yield numbers most useful to engineers evaluating products from a single manufacturer's catalog. But they can help us in a roundabout way in our comparisons of products from different manufacturers.
In order to navigate the sea of marketing numbers we're likely to encounter, let's start by clarifying what questions we actually want to be answered.
In general, we'd like to know the following:
- What the basic input and output units are
- How well the fuel we put into a heater gets converted to heat
- How much of that heat is usable
- How much of the usable heat makes it where it's desired
- How much of the delivered heat is from infrared
- How much of the delivered heat is the right infrared
- How well does that heat do its job once it arrives
Being clear about which performance parameter we're thinking about is important. As we'll see, a manufacturer may refer to any of these when advertising a unit's "efficiency." But, we have to be careful. It only makes sense to compare identical measures across appliances. Not only that, but some measures only have meaning for certain types of appliances but not others.
In some cases, there may even be both a "radiometric" (physics) term and a different heating industry term for the same number. Most importantly, though, no one metric neatly sums up any heater's overall performance.
BTUs and Watts
We've spent a lot of time talking about radiant "energy." But how do we measure it? We know we'll need it if we want to compare how much "energy" we pay to put into a heater and how much "energy" we get out of it. It turns out there are two ways to do this.
- Electrical meter
If you lift a box from the floor to your waist, you expended some energy. You might even say you did some work. In fact, that's one of the ways we can talk about energy: "work." Work tells us how much energy we used to move a certain amount of mass a certain distance. When we're thinking about heating, we consider the amount of "work" it takes to move a certain volume of a substance (like water or air) a certain number of degrees up the scale. One BTU will move 1 cubic foot of water at sea level from 60 ℉ to 61 ℉.
Back to our box example, we'd say someone who couldn't lift that box faster or more time per hour is more "powerful" than someone who could keep pace. That's the other way to measure "energy": power. Power lets us compare how long it takes to do "work." A watt is enough "energy" to move 1 gram 1 meter in 1 second.
You'll typically see watts used to measure inputs and outputs for electrical appliances and BTUs used for gas-fired ones. It's important to remember to keep in mind what you're comparing if you're looking at appliances using different "energy" scales. The "BTU rating" you may have seen on appliances is actually a measure of BTUs per hour. That's handy because it allows us to make comparisons to watts. One watt is the same as 3.413 BTU/hr. Those both measure power. But, if you come across a kilowatt-hour (kWh), that's a measure of work and should be compared to a flat BTU.
Our second question is the one of combustion efficiency. It tells us how completely fuel is burned. Put another way, it tells us how much of the potential energy in a fuel is converted into heat. Gas-powered heaters may have a combustion efficiency anywhere from 60% to nearly 100%. Vent-free appliances tend to be around 100%. As we will see, this is just one of several numbers a manufacturer may advertise as an appliance's "efficiency."
Notice that this only tells us what is happening directly at the heat source. We'll inevitably lose some of the heat from the heat source to the appliance itself through conduction and to the environment through convection. It's usually a very small amount. But, at any rate, that lost heat isn't really usable. To take those losses into account, we'll need a slightly different measure.
When those losses are taken into account the resulting percentage is called the thermal efficiency. This measure attempts to account for whatever heat is left over after combustion inefficiencies and appliance heat loss and available to be applied to the target area. Of course, if the appliance cabinet's hot temperature also contributes to heating our desired area, it's not exactly "wasted heat."
- Home energy efficiency
A unit's thermal efficiency, for this reason, maybe very close to the heating element's combustion efficiency. It doesn't make much sense to talk about the "combustion efficiency" of an electrical resistance heating element. In that setup, though, the first law of thermodynamics assures us it's safe to assume all the electric energy supplied to the heating element ends up as heat. This is where you may have heard that heating appliances with electrical resistance heating elements have (near) 100% thermal efficiency.
Considering how much of the heat makes it where it's desired is a little trickier. With a convection heater, we know that there will be some useful heat loss through the ducting and that a lot of the warmest air that is eventually supposed to heat us ends up at the top of the room. Figuring out an efficiency requires some advanced computer modeling.
The situation is similar to infrared heaters. We'll need to consider their view factors. Recalling our flashlight analogy, there's not only the "beam shape" to think about. We have to remember, too, that radiant power decreases with distance. The amount of energy a heater puts out is steady. But we'll experience less of it per square foot as we get further from the source and its beam widens. It's also worth considering that even if we aren't directly inside the beam, our surroundings will also be warmed in proportion to their absorptivity.
You can see how quickly this gets complex. On this front, though, many manufacturers are good about providing a diagram of a heater's view factor so you can position it or figure out how many you'll need to cover a space. Don't be surprised, though, if you come across an "efficiency number" for this. In fact, this is sometimes reduced to "watt density."
At this point, it makes sense to ask how much of the heat from an infrared heater is distributed as infrared. Remember that there's still some convection going on – any air that happens by that hot heat source will get warmed up, decreasing the amount of energy left to send out as infrared. Some heaters intentionally exploit this for room heating benefit while others try to minimize or eliminate it.
There do happen to be a couple of ways to measure what proportion of the heating action of a heater is radiant.
The ANSI and AHRI developed Standard 1330 in 2015. It assigns a rating to a heater based on how much of its heat is delivered by radiant energy. You may see one of two ratings: Infrared factor (IF) and radiant emission value (REV). IF is the older rating system, which was replaced because the testing equipment manufactured for measuring it turned out to be inconsistent. In some cases, there were differences of 10% between repeated test results for the same heater. REV is the newer method adopted in 2018 and is more accurate. You may see either one in practice.
Both ratings are based on similar testing procedures and calculations, however. A heater is placed in front of a radiometer, which is a sophisticated machine to measure radiant output. From the test results and quite a bit of calculation, a ratio of radiant energy that made it to the radiometer to the total energy input can be determined. New testing equipment was manufactured to ensure consistent results with the REV method.
IR Factors can range from 7 to 15, and REV's from 80 to 120. Both systems indicate a range of roughly 30% to 70% radiant heat transfer (as measured by a gross radiant coefficient), implying that the rest is transferred by conduction and convection. It's important to note that Standard 1330 testing is not mandatory; it's only voluntary. So, not every appliance will have this rating. In addition, 1330 is only applicable to gas-fired heaters whose energy can be radiated into a single measuring plane.
So, this won't help make comparisons between gas and electricity-powered units. Last, a higher REV doesn't always mean a "better" heater. This is because REV doesn't tell us how "hot" the heater is or how much of each band it puts out. It just tells us what percentage of the heat that ended up in the target got there by radiation. So, be sure to consider these aspects when you see manufacturers use this "efficiency."
Another way a manufacturer may advertise its heater's radiant efficiency is by giving the emissivity of the emitter or the heating element. Emissivity is actually a value, the ratio of how much radiant energy an actual body emits at a given temperature versus how much radiant energy it's theoretically possible for an ideal substance to emit at that temperature.
- Particulate emissions
The theoretical ideal substance used as the comparison to determine the denominator of that ratio is called a black body. Think of emissivity as a unit-less number expressed as a decimal. A perfect black body would have an emissivity of 1. This is why you may also see emissivity expressed as a percent when used as an "efficiency" in marketing materials.
When you see manufacturers use this as their "efficiency," remember that it only tells us how well the emitter or heating element works to emit infrared. Keep in mind, too, that for full context, we can really only compare emissivity of one material to another at some specified temperature. Remember, an object's emissivity gets closer to 1 as it gets hotter. For example, a nichrome filament may have an emissivity of .90 when heated to 392 ℉. But that same filament would have a .97 emissivity when heated to 932 ℉. Just like REV, emissivity also doesn't say anything about the total energy in as compared to the total energy out.
The last performance area we want to understand is how an infrared heater affects us and our surroundings. More specifically, we want to know what we can measure to let us know it's working. If we were thinking of a convection appliance, this would be rather straightforward. We'd simply look at the thermostat temperature. We've habituated ourselves to associate our degrees of comfort with the degrees on that dial. But, since an infrared heater isn't heating the air, does the air temperature of the room still apply? The answer can be found in the elements of thermal comfort we discussed earlier. Let's go through them briefly and see what metrics are there.
The sneaky trick behind the magic of comfort heating surprises most people. The secret is that comfort heating work largely flows in a direction opposite to the one we tend to think it does.
As a result of our metabolism, our bodies constantly produce heat long as we're alive. And, we need to be able to lose some of it in order to stay comfortable. Otherwise, we overheat. But, if we lose heat too fast, we feel cold. So, much comfort heating becomes about slowing the rate at which our bodies lose heat so we don't feel cold.
- Infrared thermometer
Unless we're standing close enough to it to feel uncomfortable, a convection heater isn't increasing heat in our bodies at all. Its job is to keep our surroundings warm enough that we only lose heat at a comfortable rate.
There isn't a handy tool to measure metabolism in everyday life, and that's fine. It's not even a big deal to know that we crank out about 400 BTUs/hr when we're just sitting around. But, knowing that keeping warm is actually about managed controlled heat loss is critical for everything else to make sense.
Dry Bulb Temperature
This managed heat loss process works through both convection and radiation. We're used to the convection side of it even if it's not obvious at first. But, it becomes clear when we think about it. Although most of us feel comfortable in a room full of 70 ℉ air, our skin is 92 ℉. The air can't heat us up because heat transfer only works in the opposite direction, from warmer to cooler. So, our bodies lose their extra heat to the air through convection, even in "warm" rooms. We feel "warm" because we aren't losing too much heat to that air too fast.
The technical name for a device that measures air temperature is a dry bulb thermometer. So, this number, the one on our thermostats, is called the dry bulb temperature.
But we're already familiar with this one, so let's look at how this works on the radiant side of things.
Mean Radiant Temperature
Radiant temperature is the temperature of an object measured by the amount of infrared it emits. Rather than a dry bulb thermometer, the radiant temperature is measured by a pyrometer. You may have seen these devices labeled as "infrared thermometers" in the hardware store.
If you've ever leaned over a cold freezer with the lid open, you've experienced why the radiant temperatures of objects around you matter. You may have thought the chilling effect you felt was due to cold air rushing up from the freezer. But, cold air tends to sink under warmer air. So, while some cold air may have been swirled up towards you as you opened the freezer lid, that lingering cold feeling on your face was from something else. Remember how infrared will always radiate from a warmer body to a colder one? You felt cold because you were losing heat quickly through radiation to that freezer.
- Man shivering
So just like with the freezer, we continually lose heat to cooler objects in our surroundings as well. Those objects include surfaces, like floors, walls, and ceilings, as well as furniture and other objects. This is one reason why well-designed indoor radiant systems often intentionally heat floors, walls, or both.
Mean radiant temperature (MRT) is the average of the radiant temperatures of all the objects in a room. And it can be measured with a device called a globe thermometer. Some manufacturers of infrared heaters even provide globe thermometers, too. This allows their customers to measure and manage "object" temperature the same way they would air temperatures with convective systems.
So, it turns out we have two "pumps" we can use to manage our controlled heat loss. This has two big consequences. First, we might expect that losing heat more rapidly through one method than the other would feel "strange." In fact, this is exactly the case. When air is warm but the surrounding surfaces aren't, we feel a chilly feeling akin to clamminess. Second, we might expect that if both "pumps" are working well, neither pump needs to be working quite as hard as it would on its own. This, too, turns out to be true. In a room with a decent mean radiant temperature, we feel as comfortable as we would in a room with a 3-5 ℉ higher dry-bulb temperature. This means we can set our dry bulb thermometer lower.
This relationship between dry bulb temperature and mean radiant temperature is so important that it gets its own word. The average between the two, weighted for convective and radiant transfer, is called the operative temperature. For most rough calculations, the weighting is omitted. This number is used fairly frequently in infrared comfort heater literature. It is also something ASHRAE uses in its guidelines for designing heating and cooling systems correctly.
In the same way that our bodies are continually losing heat to their environments, they're losing moisture, too. Our skin, nostrils, throat, eyes, and nasal passages all need moisture to function properly. Some water is always evaporating from those tissues, just like water evaporates from a glass left out to sit. And, just like with heat, when we lose moisture faster than we can replace it, it's uncomfortable. We dry out.
The amount of water in the air determines how much water can evaporate from our bodies' tissues. We call the amount of moisture some air is actually holding compared to how much it's possible for it to hold at that temperature its relative humidity. If you have an indoor digital thermometer with a humidity readout or a humidifier with a "hydrostat," then you're familiar with this percentage.
By allowing us to keep the air temperature 5 degrees lower, it improves the relative humidity of the air in a room. This means we don't have to add as much moisture to it to feel comfortable.
It's fairly easy to grasp that the less moisture is in the air, the more moisture we have the potential to lose. But if we really want to understand why we dry out, especially when it's cold, it helps to look at one more number.
When we start with the dry bulb temperature and the relative humidity of the air, we can derive how cold that air has to get in order for the moisture in the air to condense back into droplets. That temperature is called the dew point. You may have heard the local weather person talk about this even more than the humidity.
The beer you pull from the fridge "sweats" because it's colder than the dew point temperature of the room you're in. The lower the dew point of the environment is, the less condensation your beer will accumulate. On the other end of the scale, though, the lower the dew point is, the more evaporation is possible. That is, the lower the dew point, the drier the air feels. The bigger the difference in the temperature of the air around us and the dew point temperature, the faster we evaporate water and the more dried out we feel. Our bodies actually feel that rate. So, even when it has high relative humidity, like after a winter rain, cold air feels so dry because it has such a low dew point.
The cold outdoor air that comes into our homes through natural ventilation has that same low dew point. We can heat that air all we want to try to feel more comfortable. But until we add moisture to it, its dew point will remain the same, and we'll feel dry.
Dew point also tells us why cold exterior surfaces in a home can be subject to condensation even in winter. When we heat the air first, the walls and windows are the last to warm up. This means they risk staying at or below the dew point longer. In fact, in some buildings, some exterior walls or slab floors may never warm up without some help.
So, by first heating surfaces like walls to temperatures higher than the dew point, infrared heaters have the potential to reduce or eliminate that condensation issue. Less condensation means less mold, fungus, and bacteria.
Infrared Heater Styles
Infrared heaters come in a myriad of shapes and styles, even within the comfort heating niche. In fact, the types can look so different from one another that it's possible to have two side by side without knowing that both were infrared heaters. In this section, we'll see how to recognize the various styles and peek at where they're used and what each is best for.
The most straightforward way to divide up heaters is by their emitters. It's usually the most recognizable or prominent feature of a heater. To an extent, they even determine the shape of the main appliance cabinet. We covered emitter types already. So, you'll recall that the main emitter types are: quartz tubes, metal sheaths, metal or ceramic plaques, metal tubes, and flat panels.
Quartz Tube Heaters
All quartz tube heaters run on electricity, which heats the resistance filaments running through their emitters. You may see these long rectangular heaters referred to as "lamp" style heaters. That's apt because many of them look more or less like chubby fluorescent light fixtures with glowing orange heating elements. The reflector typically lines the inner surface of the main housing behind the emitter. In front of it, there's usually a wire cage to prevent inadvertent touching.
- Bromic heater with a cylinder heating element
Makers are able to use quartz tubes for a wide range of applications. Different models of quartz tube heaters strive for different balances of IR-A and IR-B for projection from a distance or colder outdoor use, and IR-C for absorptivity. And their electric filaments reach their target temperatures in just seconds. These emitters are easily adapted into outdoor models, which feature weather-resistant stainless steel or powder-coated housings.
Outdoor Overhead Quartz Tube Heaters
Many heaters mounted in ceilings or coves or outdoor zones are quartz tube or lamp style heaters. Terraces, large pergolas, and an outdoor dining or entertaining areas all benefit because they occupy no floor space. The higher-intensity models can even be positioned further away from target areas. Since they can be placed about anywhere electricity can be supplied, you'll see models made for garages and even boats.
Quartz tube heaters have some of the highest operating temperatures of infrared heaters. So, the hottest high-intensity models may require higher mounting and larger clearances. It's also worth checking the approved uses of models of this style. Some commercial and industrial use units are not approved for residential use.
Outdoor Floor Stand Quartz Tube Heaters
Because the lamp style is so versatile, some manufacturers make versions of it for settings where mounting overhead is not an option, too. These models share many qualities with their ceiling-mounted kin. But since they're positioned closer to their targets, you won't find high-intensity lamps.
- Pole-mounted portable infrared heater
This makes them better suited to outdoor "areas" than to larger zones. They must, of course, be placed in the cord's length to an electrical supply. And, they'll take up floor space. On the other hand, many are portable so they can be deployed and stored as needed. Even the more permanent ones are mounted atop a pole, which minimizes their floor footprint.
Indoor Overhead Quartz Tube Heaters
Quartz tube lamps can even be adapted for indoor use. While they look and work much like the outdoor models, the residential versions you're likely to only see are for garages. They're more commonly used to heat individual work areas, like workbenches, entryways, and exits in industrial buildings. You may have seen these heating stadiums and sports arenas.
They're also popular for heating large open buildings with high ceilings, like warehouses, aviation hangars, and fire stations. Some are even specifically designed for saunas, which is where you may have heard the term "IR cabin." As with the outdoor models, you'll want to check whether the approved use is commercial, industrial, or residential.
- Wall-mounted infrared heater
Residential Indoor Space Heaters
Quartz tubes also find use in most designs for infrared personal space heaters. Even though all have the signature orange glow, their shapes and sizes are only limited by manufacturers' imaginations. You'll see them in cabinet styles, tower styles, and even "circulating fan" styles. The heating element and emitter are hot, though not as hot as those for outdoors or long distances. So, they do have a safety cage on the front. Despite that, these appliance's cabinets typically aren't hot to the touch.
A blower fan is a common feature among residential space heaters and they serve two purposes. While this type of heater still exploits infrared, their radiant output is less than other styles. Since a larger portion of their heating power is convective, the blower helps distribute the warm air. In addition, the blowing action helps to disperse heat from the cabinet. You may see this kind of heater advertised as "dual radiant and convective" or something similar.
These inexpensive heaters are popular for heating bedrooms and living spaces in homes.
They're typically portable; even the larger ones may have wheels. And it's easy for manufacturers to pack extra features into the cabinet models. For instance, music speakers are frequent bonuses. As great as they are though, it may be hard to take full advantage of infrared's benefits with them. When they sit on the floor, it can be tricky to get a view factor to adequately cover a target area.
Metal or Ceramic Plaque Heaters
Plaque heaters are always gas-fired and come four basic styles. They are almost always recognizable by a glowing orange "plate" that you can tell has little holes all over it when you look closely. That said, metal plaques won't always glow. But if the heater you're considering runs on gas and has a perforated emitter, there's a good chance it's one of these.
Overhead Plaque Heaters
If you've heard the term "box heater," this is the kind of appliance it refers to. Its arrangement of rectangular glowing orange plaques bordered by a large protruding reflector makes it look like an open shoebox. Since these are hung from a height, their emitters will try to balance IR-A for distance and IR-B for absorptivity. Their plaques are almost always ceramic.
Although they may need both gas and electricity supplied from overhead, these are a popular choice in large garages and open bay buildings. They can be aimed diagonally and may even be aimed within a range of angles.
Because they operate at such high temperatures, some models may not be used in residences. It's a good idea to check a model's manual for where it can and can't be used. Indoor swimming pools and outdoor areas are two locations that might be off-limits.
Mushroom Top and Cylinder Heaters
These might be the most familiar style of outdoor patio heater. Mushroom tops look a bit like floor lamps. But where there would be a light bulb at the top of a lamp, infrared heaters have a cylindrical metal plaque emitter. The mushroom's "cap" is actually a reflector to direct infrared down to people and to help trap a bubble of warm air. The emitter on some models runs the majority of their height, essentially replacing the stem.
- Portable gas heater
A newer design even looks like a skinny pyramid with a clear glass tube at its center. Flame runs up the tube to the plaque emitter. But, in the process, the heated glass tube also acts as an emitter while adding a stunning display. The reflectors at the tops of these are usually small and rectangular.
One drawback to this heater style, however, is its limited range. Their emitters are smaller in comparison to those of other outdoor heater styles. On top of that, the emitters on floor stand models are above head height and aimed outward. Infrared must be reflected back down to the target rather than initially directed at it.
Floor stand mushroom top and cylinder heaters have provided residential and commercial area heating since 1961. Found in both portable and fixed models, they give potential users the option for either gas plumbing or propane tanks. Recently, some manufacturers have even shrunk this design down to tabletop size for home use. In any size, most of these heaters are not only familiar but attractive.
Tank Top Heaters
A tank top heater looks just like a box heater, except that the box attaches directly to the top of a propane tank. This makes it easy to move from place to place. It's easy to see why this style heater is a favorite for construction sites and other outdoor work areas. And the view factors and watt densities of their glowing ceramic plaques tend to be perfectly matched for the task.
As their name implies, these heaters are mounted between floor and head height on a wall in a home. They're a common alternative to blue flame heaters. Like them, some even have an available fan option. In front of the glowing ceramic plates is a metal cage to prevent users from touching one by mistake.
The more furniture impedes their view factors, the less infrared benefit makes it into a room. But, they are so convenient to install and have such short response time that they are a staple for zone heat in many parts of the country.
Metal Tube Heaters
"Tube brooders," as they're called, are always low-intensity heaters. They emit longer wave infrared, which is known to be the best for comfort heating. These are always mounted overhead. Just like a box heater, a metal tube heater has a reflector around its edge. Unlike a box heater, though, it doesn't glow. In their long history, they've picked up as many nicknames as there are places people have found to use them. Some of the others you may have heard are "push tube heater" and "stick heater."
It's worth considering that their overhead position does require gas and electricity to be available from above. And, while not a concern for most units, the temperature can decrease quite a bit down the length of the longest tubes. A low-intensity output heater will also have the most trouble overcoming high winds or outdoor cold.
But because they produce gentle comfortable heat, metal tube heaters see lots of use in the seating areas of retail centers and restaurants. For their insides, warehouses or plants may have them custom-designed to canvass an entire building. Or they may use standard models to only provide heat in zones where people work. Either way saves valuable floor space. This style is so trusted for industrial open bay-like areas, it's no wonder they've become popular for home garages, too.
Flat Panel Heaters
Of all the styles of an indoor heater, flat panel heaters may be the "coolest." They not only operate at the lowest temperatures, but they are also the most stylish. Thin and rectangular, they can be hung on walls or suspended from ceilings. There are some that fit into ceiling coves. They can have bars fashioned onto them when they're built as bathroom towel warmers. And, some are disguised as functioning mirrors. A handful of companies even offer custom prints on the fronts so they can double as wall art.
- Infrared portable heater at a restaurant
These are favorites of infrared specialists heating living and office workspaces. Their profiles are slim, they run on electricity, and their response time is quick. So, they're easy to work into building-wide zone heating plans. While most panel heaters are of the low-intensity type, there are some medium intensity models, too. They may be preferred in high ceiling rooms used as recreational spaces. Hot yoga studios, for instance, are growing advocates.
Flat-panel heaters overcome most challenges using infrared in "normal" spaces. But since they can melt into a background unique care is due. They're still heating appliances. Even though only prolonged contact is likely to cause burns, their surfaces are still hot to the touch.
Infrared heaters for most uses are sized for parcel delivery. They're light enough to be delivered to your front door and don't usually require a signature.
As with any appliance, however, take into account the fact that yours has been on several loading docks and many freight trucks before getting to you. Be sure to consult your installation manual thoroughly. There will be checks and adjustments to go through to make sure your appliance works the way it should.
Even though it's only necessary in a small number of cases, be prepared for some cleaning in tight spaces or tweaking rather than a complete plug and play experience. This is especially true for gas-fired appliances and is why most manuals insist that installation and service be performed by knowledgeable professionals. There may be a little more to do than just making the utility connection.
You'll recall each unit is a unique combination of energy input, heating element, emitter material, and reflector design. This leads to different view factors and watt densities in the desired wavelengths. This also means there is no one-size-fits-all positioning or appliance sizing for all heaters or even to any heater types.
- Outdoor patio area
But, in a general way, you can think about "aiming" an infrared heater the same way you would a flashlight or a light fixture. If you put a radiant heater low to the ground in a spot where its "light" is blocked by furniture, you won't get its full benefit. Anywhere there's no "light" will stay cold until heated by the convection or conduction from the rest of the room. This is why many models are designed to be placed at height and "shine" heat down on target areas for the broadest coverage, just like traditional lights.
In every case, it's best to consult the model-specific documentation. Remember that considering watt density alone may not be enough. 20,000 watts of high-intensity infrared need to be positioned differently than 20,000 low-intensity watts.
Single appliance installations in residential settings are ones most homeowners should feel comfortable tackling themselves. But, the situation is different if we're considering a multiple appliance installation as part of a well-designed zone heating plan. In this situation, you should take advantage of the manufacturer's in-house design service whenever possible. If you can find one, you'll also benefit from consulting with an installer who has previously worked with the brands or models you plan to install.
Fuel Access and Cost
It's tempting to let yourself get swept up in claims about energy savings. But the hard truth is that both the cost and availability of fuel gas and electricity vary by region. So, if you're planning on doing a cost comparison, be sure to check with your utility provider and check your desired product's installation manual for consumption information.
- Outdoor natural gas line
Routing fuel gas or the right voltage of electricity to a planned appliance location may also be restricted by a building's layout. Consult with your gas plumber, electrician, or general contractor to make sure you don't run into any surprises.
Ventilation, Clearances, and Avoiding Burns
No matter what type of infrared heater you're thinking about, your choice of its final location will also need to take into account ventilation, clearances, and avoiding burns.
If you're considering an indoor gas-burning appliance, you'll need to plan for adequate ventilation. The goal is to make sure there's enough oxygen to maintain combustion without depriving humans of what they need for respiration. Ventilation also provides dilution and evacuation of combustion by-products.
Gas heaters classified as "unvented" don't require any special vent pipes to carry fresh air to the appliance or to carry exhaust to the outside. When operated properly they only produce the same "exhaust" gasses human beings do. Still, though, they require proper ventilation, and indoor units should not be installed in what are called "confined" spaces. Residential appliances need a minimum fresh air opening of one square inch for every 1000 BTU/hr of burner capacity for proper ventilation. Unvented appliances also don't operate well above 4000-4500 feet because the air already has less oxygen.
- Portable infrared gas heaters
How far manufacturers specify an appliance must be from combustibles in each direction also affects its placement. Failing to follow these specifications puts you at risk of starting a fire. What often isn't given enough weight is that a fire may not result for months or years after the installation. Manufacturers will also spell out how to position their models so as to minimize the risk of burns. Even though many have safety features to prevent directly touching an open flame or high-temperature emitter, leaning against a hot housing or emitter panel could prove to be painful.
Some requirements may be a little different from model to model, so always be sure to check the documentation. Your installation planner or installer is a good resource to double-check with, too.
Care and Maintenance
Something to love about infrared heaters is that they don't have many parts to wear out. In fact, electric heaters without fans may only require occasional bulb changes and dusting.
As straightforward as they are, you'll still want to keep a couple of things in mind when tending to an electric infrared heater. First, make sure the appliance has been turned off. Also, it needs to be disconnected from its power source and cooled to room temperature before performing any maintenance. And, second, never handle quartz tubes or bulbs with your bare hands. The oil from your skin can cause hot spots on the tube surface, which may shatter when the appliance is turned back on and heats up to temperature.
- Plumber fixing gas line blockage
While the maintenance of an electric heater can typically be performed by the homeowner alone, gas-fired heaters require a bit more attention. Their valve trains should be checked at least once a year. And it's a good idea to have a certified professional gas appliance technician do the heavy lifting. In this respect, they're just like any other gas-fired appliance in your home or business.
Gas supply hoses will need to be checked for wear. You'll want to compare the flame pattern on ceramic and metal plaque burners to the pattern in the installation manual to make sure its right. There shouldn't be any blue areas. Burners of any type should be cleaned with compressed air, particularly in their air intakes or shutters. Injectors, housings, and control compartments, too, benefit from being cleared of dust.
With all the information presented in this article, you're well on your way to earning a certification in infrared heaters! Just know that a well-built gas-fired infrared heater can reasonably last 15-25 years. Radiant panels, which are essentially a solid-state design, can even last 40 years. The only heater type with parts needing regular replacement is quartz tube heaters. While some have longer life spans, 5K hours is a good average tube life. For comparison, there are 8740 hours in a year. If you still need more clarity, our NFI certified technicians are more than happy to assist you.
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Infrared Heaters Q&A with the NFI Certified Specialists* Please Note: All customer questions are answered by our NFI Certified Specialists free of charge!
from New York asked:
October 1, 2019
Do you carry portable infrared heaters that do not require electric?
We do not carry any non-electric portable heaters.
on October 2, 2019