Infrared Heating for Homes: Is It The Right Choice?

As a provider of an electrical infrared heating solution who’s now done installations in multiple countries and vastly different markets (Germany, UK, China, and Turkey) over the past four years. I’ve encountered a lot of false information/misconceptions about infrared heating that have been promoted by not only direct competitors in the building heating industry but also other suppliers of infrared heating!

Now I know it’s the norm to try and position one’s product as advantageously as possible while simultaneously downplaying the product features of one’s competitors. However, the built environment is incredibly complex with a one size fits all solution not existing for any part, let alone heating! That’s why in my opinion it is incredibly important for people to understand the true pros and cons of solutions such as infrared heating, heat pumps, water led radiators etc.. so that when they are making the decision on which heating solution best fits their specific project they can make an informed decision!

So, with that in mind I wanted to take a bit of time and lay out from my experience how infrared heating really works in the heating of spaces, in what situations it works and in what situations it doesn’t really work, as well as comment on some common claims for and against infrared heating! Now infrared heating solutions can be water based (hot water acting as the heat source) or electrical (a resistive element generates the heat) and I’ll mostly be referring to the electrical version below.

How does Infrared Heating Work in The Heating of Spaces?

Infrared Heating, especially electrical resistive heating works through allowing an electrical charge to pass through a resistive element (usually metallic or carbon based) which then generates heat (These solutions according to The UK's SAP 10.2 guidelines are considered 100% Efficient (in terms of 1”unit” of electricity turning into 1”unit” of heat). This generated heat then in turn increases the surface temperature of the material above it through conduction which then is able to emit out waves of radiative heat which in residential home heating applications nearly always fall into the far infrared portion of the electromagnetic spectrum(this wavelength isn't capable of penetrating human skin so is completely safe). The common analogy people like to use to express the heating effect of infrared heating is having people imagine the warmth that one would feel will standing underneath a spring sun. Which I have always found to be a rather apt comparison!

The proportion as well as total amount of heat that is emitted as far infrared waves, versus say being absorbed by the air and creating a convective heating effect, is generally dependent on the following three things:

Surface Area:

The greater the surface area of a radiant heater the greater will be the total amount of radiant heat (other variables being kept equal). This should be relatively intuitive with many suppliers of infrared panels offering increasing sizes of heaters equating to higher wattages with those higher wattages directly equating to more heat!

Surface Temperature:

With infrared heating solutions, in general the higher surface temperature you reach the higher will be the proportion of heat that is emitted as far infrared radiative waves. From my experience and our own tests this equates to in general the below ratios when it’s the same area(and the emissivities of the surface are similar)

1. 26-28C (average underfloor floor heating surface temperature) 25-30% radiative heating 70-75% convective
2. 42-45C (common wall radiative temperature in Germany for electrical heating film solutions) 45-50% radiative 45-50% convective
3. 55-58C (common target ceiling surface temperature for radiant systems) 55-60%radiative 45-40% convective heat transfer.
4. 90C (common surface temperature of a single panel space radiator) -70-75% radiative 30-25% convective heat transfer.

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As you can see as surface temperature increases so to does the proportion of heat that is emitted as far infrared waves. So if one’s sole goal is to maximize radiation then getting the surface temperature as high as possible is a rather good strategy.

But if that’s the case why doesn’t everyone just design their elements as hot as possible? Well, the reason is a combination of safety (touching things above 100C tends not to be very pleasant), structural: the heating elements and cassettes that contain them struggle at very high temperatures, not to mention any surrounding building materials (plaster/plasterboards/wallpaper etc.), and comfort(especially thermal comfort) playing a role with there being some nice references in ASHRAE 55 to some studies that indicated a noticeable increase in the number of individuals feeling uncomfortable in a space once the surface temperature of radiating bodies start to exceed 60C. Now besides surface temperature and surface area the last big influencing factor is emissivity

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Emissivity: How Sunlike Is The Material?

This refers to an object’s ability to absorb and emit radiation. This value lies on a spectrum of 1 (also known as a Black Body, which has perfect absorption and emission characteristics) to 0 (has absolutely no ability to absorb or emit radiation). An example of a material that has extremely good emissivity is our skin which sits around .94 whereas an object with an extremely poor emissivity value is aluminum foil with a value of around .03. This is important to understand because when designing radiant systems this can potentially play a major role. For example if you have a radiant panel that is designed to reach 60C surface temperature (in normal working conditions) but say cover it with an aluminum foil the surface temperature will reach 100c+ and have almost no radiative heating effect!

Now luckily most building materials/surface finishes sit at emissivities between .8-.9. However occasionally this can cause a really large difference (heck, 10% is already quite substantial!). This is without a doubt a part of heating design, especially for radiative project design, which still needs a lot more work to be done in order to maximize performance.

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Emitted Heat Gets Absorbed

So now taking the above into consideration say you have an optimized radiative system installed. The heat is primarily emitted out as far infrared waves and moves through the space and the speed of light making contact with the surrounding surfaces. These surfaces then in turn absorb the radiation and increase in temperature. Through this process the average temperature of the surfaces in a space increases and leads to the scenario wherein one can feel comfortable even at 1-2 degrees lower air temperature than one is normally used to. This is especially relevant when one considers that our bodies goal in cold environments is actually to minimize heat loss and that we primarily lose heat through radiation. Meaning that by increasing the surrounding surface temperatures we reduce our radiative heat loss and thus feel more comfortable at “lower” temperatures! To highlight this point we’ve also made a short animated explainer video in the past which explains the above concepts if you prefer videos!

So now that hopefully you have a general idea of how radiative heating works and what variables affect it lets take a look at when radiative heating systems work well and when they don’t!

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Disclaimer*

First, let me just say that for any single heating solution one of it not the most important aspects is project design. It does not matter how efficient the heating solution can be if it is grossly undersized for the specific project at hand. It doesn’t matter if it’s a Heat Pump, Radiant Panel, Small Electric Convective Heating, Full Radiant System, or Gas Boiler. Undersize for the project at hand and you or your customer will rack up a massive energy bill AND not reach a comfortable indoor temperature!

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So When Does Infrared Heating Work Well and When Doesn’t It?

First let’s assume that projects are generally properly designed to account for the actual heating requirements of the space (meaning you’ve installed the proper wattage). In that scenario we’ve found that the following three variables play the biggest impact on how effective the infrared heating solution can be

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1: Insulation:

Insulation as we know serves to reduce the rate of heat loss (through conduction/convection/radiation) from indoors to outdoors in cold environments. It’s nearly impossible to reduce it to zero but we’ve been able to develop materials that do a really good job in some cases (think Passiv Hauses). This is important for infrared heating solutions because Infrared Heating Systems are either installed on the surface of the room (think standalone radiant panels) or a couple of mm up to 1-2cm for embedded radiant floor/wall/ceiling systems. This becomes really important because if for example you install a radiant embedded system onto a wall wherein there is minimal to no insulation then almost 40-50% of the heat may end up moving not into the room where it is needed but instead out of the house through conduction (For a great video describing convective heat transfer check out the efficient engineer’s video on youtube!

However, in a properly insulated house and with proper heater design one can get up to 80-92% of the generated heat to be released into the room wherein it is needed. This is really where the efficiency of the system starts to shine, especially when compared with any heating system that generates the heat outside of the room and needs to transport it into the room(since there is near constant heat loss during the transportation process) such as Heat Pumps, District Heating, Gas Boilers etc.. In addition, since infrared heating systems rely on heating up the surrounding surfaces if there is no insulation then those surfaces can often take a really long time or even never end up really increasing in temperature! However, if the space is well insulated then not only will the surrounding surfaces being heated heat up faster but they can also occasionally turn into a heat reservoir leading to a longer lasting warmth and less energy consumption!

So in general the better insulated the space is the more effective will radiative heating solutions be compared to alternatives thanks to their close proximity to where the heat is needed, minimizing heat loss associated with heat transport as well as thanks to the nature of infrared radiation heating up surfaces.

Besides insulation the other important variable determining the performance of the radiant system is:

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Matching The Infrared Heating Solution to the Space:

A?key thing to understand about infrared heating systems is that they need to be adjusted to the space where they’re installed in. This is due to the fact that infrared heating tends to decrease in effectiveness the further you go from the radiating source and the fact that infrared heaters radiate at certain angles which with poor design can lead to drastic temperature asymmetries in a room.

?If something is in the way of the waves the object in question first absorbs said waves and then remits a portion of the energy. This is a major reason why it’s often advantageous to have multiple radiating bodies in a room.

As mentioned in the part explaining how infrared heating functions, the performance of a infrared heating system is heavily determined by the surface area, surface temperature, and the emissivity of the infrared heaters/their immediate surface materials. It is often these variables that can directly be manipulated to match the infrared heating system to the specific differing spaces in turn maximizing performance.

Now lets take a look at a couple of different infrared radiant systems and identify in what situations/conditions they would be ideal to use.

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90C Surface Temperature Single Panel Wall/Ceiling Radiators-?These panels are in general ideal for well insulated spaces up to 10-15m2(think a bedroom) and poorly insulated spaces up to 5-10m2(think a small workspace or bathroom). In both of these scenarios the space in question does not get large enough wherein a single panel no longer suffices due to the large area and possibly large number of objects in the space. In this case however, actual placement of the panel is very important with often the ceiling being ideal to maximize the reach of the infrared waves.

Big Pros of this application are the ease of installation (generally just need to wall or ceiling mount them and plug them in) and fast reaction time of the panels. Some cons are the fact that they can cause an obvious hot head sensation which some people dislike and don’t always fit into the space’s aesthetic requirements. These panels maximize radiative efficiency but lose out on surface area coverage and some models also don’t pay sufficient attention to the emissivity of their surface finishes impacting efficiency. In my opinion this solution is ideal for bathrooms and small rooms.

*Especially for single panel heaters there can be a large difference on efficiency of the heaters depending on what heating element is used. The two types tend to be film or wire, with film tending to be 25-30% more efficient due to having a more homogenous heating effect.

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55-58C Ceiling Embedded Radiant Systems –?This system using either panels, film, or wire that is embedded into the ceiling is designed in such a way to find a balance between radiative effectiveness (reaching 60%) and surface area coverage (usually needing about 15-25% surface area coverage) in order to get the proper heating effect depending on the projects heating load. This increased surface area coverage, in contrast to single panel radiators, also helps avoid some issues such as temperature asymmetries. An example of this system is our PowerBoard System.

However, this solution’s downside is that it isn’t suitable for projects with ceilings higher than 3.5M height due to the increased distance between radiant surface and surrounding surfaces as well as the fact that some additional care needs to be taken to concentrate some heaters near larger heat loss sinks (such as drafty windows or doors).?This solution is in general ideal for most projects that are at least decently to well insulated.

25-30C Floor Radiant Systems –?These systems, although they lack in surface temperature limiting the percentage of heat being emitted as infrared waves (25-30%) they make up for it with surface area generally covering about 70-80% of the surface area in order to achieve the needed heating effect. These systems are great for spaces wherein ceiling height exceeds 3.5M, customers want heated floors specifically, or insulation is a bit on the poorer side (since a proportion of the heat is also passed along as conduction via the feet). However, generally consumption of these systems is greater than infrared wall/ceiling systems due to higher heat up times and greater heat loss through the floor, as well as having more of a convective heating effect than radiative.

So ultimately for every project the proper infrared heating method needs to be determined to maximize performance. Otherwise not only does one run the risk of not reaching the proper heating effect, but the energy consumption will also be unreasonably high!

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Zoned Control/User Behavior.

The last important variable that comes into play is zoned control and the end user’s behavior. A large advantage of infrared heating systems is their fast reaction times. For properly set up wall/ceiling systems within 20 minutes one can bring a 10c room up to 23C after which point the systems will only be on 1/3-1/5th?of the time depending on the projects insulation level. This stands in contrast to most UFH(Underfloor Heating) systems which can take up to an hour if not more to reach the proper temperature and then needs to be constantly running to maintain the temperature. In practice this means that wall/ceiling infrared radiant systems, especially when partnered with smart home systems, can result in significant energy savings. These savings can be directly attributed to only heating the rooms that one is currently using, or setting the heaters to turn off when leaving the house and on shortly before returning. This reaction speed is only possible due to the heaters being often installed only a couple of mm from the surface. This zoned feature also makes certain radiant options a great choice for office spaces with functional heating being easily implemented in the spaces that are currently being used, decreasing energy consumption while also increasing comfort.

However, besides the above there are also some other situations wherein infrared heating is not always the best solution. Some example’s are spaces with extremely large window coverage (think 30%+ wall coverage by windows) as well as in poorly insulated homes with limited total power supply, wherein the total wattage draw may sometimes get quite large and require additional power supply from the grid which may prove prohibitive (although in most cases this isn’t an issue especially when the whole system isn’t on at once).

So after taking a look at when infrared heating can be effective and when it can’t let me list out some common positive and negative claims about infrared heating and my comments.

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Some Common Positive Claims of Infrared Heating:

1. Purported Health benefits associated with infrared heating such as increased immune system, increased blood flow, reduced joint pain, and reduced allergies.

For Infrared Heating, effects such as stronger immune system, increased blood flow, and reduced joint pain unfortunately lack sufficiently robust research backing it up for me to back these claims. That being said anecdotally I’ve had clients/customers who’ve made the above claims and my grandma in Germany loves laying her back against a heated wall! However, on the reduced allergies side there is a good correlation between the fact that infrared heating in part avoids drying out the air by direct heating(dryer air can dry out our mucous membranes making it easier for allergies to affect us) as well as doesn’t forcibly circulate the air in the space like must forced air heating solutions (A/C) do.

2. Infrared Heating systems are energy efficient with proven savings as much as 50% compared to other conventional heating systems.

Ultimately energy consumption will always be highly dependent on the specific project, its conditions, the outside climate, and user behavior. However, what we’ve seen is that through intelligent project design and optimization of the heaters, consumption can lie anywhere between .0018kwh/m2/hr (in a 100kwh/m2*a project) to .0008kwh/m2/hr (in a ?40kwh/m2*a project). In general we’ve been able to note anywhere from 20-30% energy savings when compared with convective solutions. The biggest reason is usually associated with reduced heat loss through avoiding transporting the heat long distances, intelligent zoned heating, and not being reliant on insulative air to heat a space. However, it should also be noted that signifigant energy savings can be gotten when combining infrared heating solutions with a Solar System. The lower upfront costs of the infrared heating system make it more economically justifiable to install a Solar System alongside it!

3. Infrared Heating systems have no annual maintenance and have a long lifespan.

This is without a doubt a major advantage of infrared heating systems. At the end of the day they are significantly less complex than alternative heating solutions. This means there is significantly less that can go wrong in fabrication of the heating elements to actual implementation in a project when compared with complex UFH systems or Heat Pumps, or gas boiler systems. To illustrate the difference in complexity of an ASHP(Air Source Heat Pump) and say an infrared heating system just take a look at either this post or picture from said post:

?Another added benefit to the fact that Infrared Systems are simple is that installation is simple as well. The level of training required for an installer to install infrared solution dwarfs that of technically complex systems such as Underfloor Heating Heat Pump systems, or standard central A/C with all the associated ductwork, not even mentioning the time required for installation with infrared solutions often taken a fraction of the time. For reference it usually takes us about 10 hours of work to install a 150m2 decently well insulated project with our PowerBoard System(including design/planning work).

Common Negative Claims of Infrared Heating:

Infrared Heaters only heat directly in front of them and create temperature assymetries.

This is where intelligent project design comes into play making sure to choose the correct infrared heating solution for the specific project’s needs. From my own experience without a doubt if you simply slap a radiative solution onto one wall in a large space you will not reach the required result. However, by choosing an embedded radiant system in said situation and spacing out the heating elements you can easily achieve the desired result!

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Infrared Heating systems are less efficient then Heat Pumps due to them only having a COP(Coefficient Of Performance) of 1 Versus a COP of 3/4 of Heat Pumps.

Whenever this topic comes up I’m always confused why it’s assumed that the infrared heaters as well as the heat pumps are isolated variables. In that situation I would tend to agree with the statement that heat pumps, at the source of creating the heat energy (at the actual compressor), are more efficient (although in winter conditions it's usually around 1.5/2COP instead of the 3/4 COP that gets tossed around). But at the end of the day these systems aren’t in isolation. Heat pumps always need to transport the heat from the compressor units into the spaces where the heat is needed. In that process of transportation there is constant loss, especially when the medium transporting that heat is water). In the case where they’re directly heating air then you not only have a high energy load of needing to heat air which by itself is insulative, but you also need to deal with the increased heat loss via air through cracks/windows/doors due to a higher temperature difference and great air movement in the space. ?In my opinion what should do the talking for the energy performance of a system is the actual energy costs for individuals, not marketing statistics designed to hoodwink laymen. There is a good comparative study of standard infrared panels and ASHP done by Jan Heider M.A and team from HTWG Konstanz called "IR-Bau" which may interest some people who want to look into the data in some more depth!

Infrared Heating Doesn’t Create a Lasting Warmth

This is again in my opinion a problem of project design. If you improperly design a project then you will be incapable of really managing to heat the space to a sufficient level wherein the heat continues to reside in the space. However, if it is properly designed then this can easily be accomplished. What’s more, over time the effectiveness of the system continues to increase with us having seen a 3-6% increase in heating efficiency in some projects in China from the first year to the second. We attribute this increase in performance to the “drying” out of the surfaces that are being heated over the initial heating season. This drying out is also why properly designed infrared systems have certain anti mould usages. Due to the lower moisture content in the walls as well as a higher wall surface temperature reducing condensation.

In conclusion, implementing an effective infrared heating solution is nuanced. Precise project design is crucial, in order to maximize performance surface area, temperature, and emissivity all need to be optimized. Zoned control harnesses rapid reaction times, fostering energy savings and user comfort, but is dependent on installer knowledge and proper project design which are essential to solving common issues such as temperature asymmetries and inefficiency—delivering personalized warmth all while being energy-efficient and maintenance-free.

As I mentioned at the start of this article there is hardly a one size fits all solution for heating in the building industry due to the huge variety of projects. That’s why we need a large catalogue of solutions that can then be tailored to match the specific project needs allowing for an optimal performance. Infrared Heating is one solution and I hope that at least the above serves to help clarify some of it’s advantages or disadvantages. But having said that we ourselves of course believe that Infrared Heating is uniquely suited to heat a wide variety of buildings;)

If you have any questions or want to know where I got any of my claims from feel free to reach out!