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Infrared heating test – a personal experiment

Infrared heaters are often discussed as an alternative to radiators with heat pumps. To find out the real story about heating with infrared heaters, I took a chance and tried it myself: As a test, I set up an infrared heating system in my office and took a close look at how effective it really was. The incredible results of this infrared heating test can be read here.

As an architect, I am grateful and happy not to have lost my curiosity over the course of 20 years of work. Time and again I deal with new materials, processes and technologies in the field of house construction. This satisfies my personal thirst for knowledge and creates lasting value through comprehensive expertise, which I am happy to bring to the construction of 1 and 2-family houses.

Today more than ever, the (mostly) young builders are spoilt for choice. The range of products and services on offer for new buildings is enormous. Countless window variants, floor coverings, electrical installation options, etc., are just waiting to be selected. Since most of the builders are laymen, I see myself as an architect with the responsibility of providing the best possible professional advice on all relevant topics. Honestly, that isn’t always easy…

Why test infrared heating?

But that’s enough of a preamble – today I report the findings from my latest project, a practical test of an infrared heating system. I wanted to experience with my own body what it would feel like to heat my office in winter with a direct electric heater.

For a long time, heating with electricity was considered inefficient and uncomfortable. We remember night storage heaters that drew ‘endless’ amounts of energy and were extremely sluggish. For more than two decades, ‘heating’ and ‘electricity’ could no longer be combined in a meaningful way for me. Only with the appearance of heat pumps did I start to rethink my position. This technology still offers a good solution, which is why heat pumps are currently the most frequently installed heating system. However, the frequently used air/water heat pump comes with some disadvantages. High acquisition and maintenance costs and the somewhat difficult process of integrating it into the exterior of a house stand in opposition to its otherwise good characteristics. This is reason enough not to be satisfied with the current technological state of established heating systems.

An infrared heating test would give me clarity about what is true about this new form of direct electrical heating. I have read a lot on the subject, although neither technical literature nor the Internet really provide extensive and, above all, reliable information. So I will set up a personal experiment and heat my office for a few weeks exclusively with infrared radiant heat.

What distinguishes infrared heating systems from established heating systems?

An elementary difference between infrared heating and established central heating systems (heat pump, gas boiler, oil heating) is the operating principle: Instead of distributing the heat through convection in a room, infrared radiators radiate heat to the surrounding walls and furniture and stimulate these parts of the building to participate in passive ‘co-heating’. Classic underfloor heating or hot-water radiators, on the other hand, heat the surrounding air, which in turn transmits heat to the surrounding bodies. Unlike radiant heating, when using convection-based heating you experience a higher air temperature and colder room components (furniture, walls, ceiling), or, for the sake of comparison, radiant heating warms the air less strongly than it does the room components at the same room temperature. I wanted to know what that would feel like. Would I even feel the difference? I expected an answer.

In my test, the infrared heater would be compared against the warm water underfloor heating system that I had been using up to this point. Which brings up another question: How would it deal with cold feet? In my personal experiment, I would also seek an answer in the form of measured values and a subjective assessment. At the time, I couldn’t really imagine (before the start of the test) how a wall-mounted heating device (middle of the heating unit approximately 1.7 m above the floor) could heat the floor just as efficiently. Personally, I hate having cold feet. That is why I am particularly curious about the results regarding this issue.

Finally, in the run up to the experiment, I asked myself how pleasant/unpleasant the periodic heating of a rapidly reacting radiator at almost head height and at a short distance of 2.8 m would feel. A short explanation: Hot-water radiators with thermostats can be controlled to a constant heating temperature and thus radiate a constant heat energy. My warm water underfloor heating is controlled by room thermostats. The thermostat contains an adjustable bimetallic strip switch that closes the control valve for the water flow in my office when the temperature reaches the target temperature and opens it again when the temperature falls below this value. Just like a sine curve, the heating changes between on, off, on, off, etc.. Because of how slowly the system operates, this is not noticeable in everyday life. We perceive the room to be at a constant room temperature. I will also measure and document the air temperature of my previous heating system over several days.

Here are some of the questions I would like to find answers to during the infrared heating test:

– How does it feel to work in a room heated with radiant heat?
– Would I perceive the air as cooler when using radiant heat? Does that have a positive or negative effect on me?
– Would I perceive the furniture and walls to be warmer? Does that have a positive or negative effect on me?
– How does the temperature of the floor change? Do my feet/legs get cold?
– Is the temperature drop during and after ventilation stronger or weaker?
– Can a single infrared radiator heat my office evenly and sufficiently?
– What does it feel like having the infrared heater turn on and off periodically? Do I notice that?

The test set-up – this is what the infrared heater looks like before installation:

A 1,100 watt infrared heater is used for the test

My test will use a 1.2 x 0.9 m infrared heater with an output of 1,100 watts. The manufacturer of the heater is the German company, Welltherm. I chose this manufacturer for three reasons:

1. In my opinion, electrical and electromagnetic fields should be reduced to an absolute minimum in terms of building biology. Thanks to counter-rotating heating conductor geometries, Welltherm GmbH reduces unwanted electromagnetic fields (information: How efficiently this works is currently beyond my knowledge. The Welltherm company also does not provide any concrete measured values. No other manufacturers seem not to have given any thought to this topic, which is important to me. At the very least, I haven’t found any information on this topic from any other infrared heating manufacturer.

2. The websites of many infrared heating companies are full of flowery promises. I find the following to be true: The bigger the talk and the more ‘marketing texts’ are directed towards me, the less trust I have in the corresponding companies. Welltherm’s website is agreeably serious and factual.

3. Three manufacturers are left at the end of my preselection process. I called all three for advice. The phone call with Welltherm was by far the best. Plenty of specialist information was provided upon asking about electromagnetic fields and efficiency through a maximum radiation factor, as well as good planning aids, ultimately convinced me to order my test equipment there.

The supplied infrared heater has a body made of white powder-coated metal. In terms of colour, structure and degree of gloss, the surface resembles a smooth surface painted with white dispersion paint, comparable to a wall clad with non-woven wallpaper, as is often used these days in modern living rooms.

The electrical connection is made via a three-core supply line into which a radio receiver has already been integrated. Usually this radio receiver is ‘hidden’ behind the heating unit; in my case, it lies separately on the floor. The radio receiver is responsible for switching the heating on and off and works together with a battery-operated radio thermostat. In turn, a three-core cable leaves the receiver, at the end of which a safety plug is mounted. Thus, the entire system should be relatively easy to put into operation. More on this later.

The infrared heating test will take place in an office

The location of the test is my 3.6 x 4 m (14.4 sqm) office, which is located on the ground floor of a two-storey building. The floor lies against the ground, since the building has no basement. With a wall thickness of 44 cm, the outer walls are well insulated for the year of construction (1998). The heating unit hangs on an inner wall leading to the hallway. My desk is in front of the infrared heater, approx. 2 m away. I myself am seated at a distance of 2.8 m from the surface of the infrared heater. My head height is aligned with the lower edge of the heater. The described arrangement is a rather coincidental result, because I find that this location is the only sensible place for mounting the heating unit. Still, I welcome the small distance to the heater for the purposes of the test, because I can perceive the radiated infrared warmth in an unreflected state, and thus directly.

Temperature measurement before the start of the test:

Before installing the infrared heater, I measure the average ground temperature with an infrared thermometer. In a series of three measurements, I measure the floor temperature at 6 points. The 18 measured values:

Measurement series 1 26,4 25,1 26,9 26,6 25,7 25,4
Measurement series 2 24,1 23,8 23,6 23,5 23,2 23,2
Measurement series 3 24,8 24,8 24,8 24,6 24,2 23,8

… result in an average floor temperature of 24.6 ºC (underfloor heating).

I also measure all 4 walls with the infrared thermometer in a series of three measurements in 6 places and calculate the average of all 18 measured values:

Measurement series 1 20,4 22,0 21,9 21,4 22,0 20,0
Measurement series 2 20,3 22,1 22,0 21,1 22,4 20,1
Measurement series 3 20,5 22,2 22,0 21,6 22,3 20,2

The resulting average wall temperature is 21.47 ºC.

Both series of measurements are carried out throughout the day with an outside temperature of 5-7 ºC. The ambient air temperature in the office during the measurement series: 23 ºC.

Next step of the test: Installation and setup of the infrared heating system

(In the picture: my good friend Jens whom I would like to thank for his help)

Installation of the heating unit on the wall is easy. In principle it is almost no more difficult than hanging a picture; it only needs a few more dowels and screws. The supplied drilling template facilitates the marking of the drill holes. Drive in the dowels, screw in the screws, hang up the heating unit, done!

Electrical setup is similarly simple. First, insert the plug on the end of the heater’s power cable into the nearest socket, then press and hold the button on the receiver for 3 seconds, and briefly teach-in and link the transmitter. If desired, save the switch-on and switch-off times and target temperatures for day and night operation on the thermostat, and the heating unit is ready for use.

Even for a layman, the infrared heating system can be installed and set up in a maximum of one hour. That’s what I had in mind – simple and self-explanatory.

First impressions and experiences of the infrared heating test

On the day that I switched from underfloor heating to infrared heating, the room’s temperature feels uncomfortable. The residual heat left in the air by the underfloor heating and the radiated heat of the infrared heater added up to an unpleasant mixture of heat. It simply takes a few days until the floor no longer emits any residual heat from the underfloor heating system, and simultaneously the room shell must be slowly tempered by the high-energy radiation of the electric heating system.

I let this conversion process run for five days before measuring the temperatures of the walls and the floor again. Enclosed are my measurements from day five after the switch to infrared heat. In three series of measurements, I again measure the floor temperature at 6 points. The 18 measured values:

Measurement series 1 20,9 21,1 21,0 20,8 20,5 20,3
Measurement series 2 21,2 20,9 20,9 20,8 20,4 20,3
Measurement series 3 20,8 20,9 20,8 20,6 20,4 20,2

… result in a average ground temperature of 20.71 ºC (approx. 4 ºC less than before).

I also once again measure all 4 walls with the infrared thermometer in a series of three measurements in 6 places and calculate the average of all 18 measurement values:

Measurement series 1 21,7 21,4 21,6 21,8 20,4 20,8
Measurement series 2 20,4 20,3 20,6 21,0 21,0 21,7
Measurement series 3 20,1 20,2 21,3 21,2 20,9 21,7

The resulting average wall temperature is 21 ºC (approx. 0.5 ºC less than before).

Both series of measurements are carried out throughout the day with an outside temperature of 7-8 ºC. The ambient air temperature in the office during the measurement series: 21 ºC.

The measured values with the underfloor heating and subsequently with the infrared heating were carried out at approximately the same outside temperatures (1-2 ºC difference) and are therefore quite comparable. What I notice: The air temperature when using the underfloor heating was 23 ºC, but I now feel comfortable at 2 degrees less at 21 ºC. Although the air temperature is lower, the average wall temperature has changed only slightly. Now you’ve heard this multiple times – the heat waves from the infrared heating system primarily heat the room (furniture and walls) and only very minimally the air. I can confirm this fact on the basis of my measured values.

Continuous documentation over 10 days shows a constant temperature level between the set reduction temperature (18.5 ºC) and the daily target temperature (20-22 ºC). During the test period I varied the target temperature several times and ultimately found the optimal value for me at to be 21 ºC. You can see that the 18th, 19th, 25th and 26th are weekend days during which I programmed a reduced heating period. In the transition of the night from the 20th to the 21st you can also see that the room did not go into the night time reduction period because I had made an error when programming of the thermostat.

The solution for cold feet

As expected, the positioning of the heater and the way in which it works means that the floor temperature has significantly reduced ( down by 4 ºC) so that I now experience problems with cold feet, and there is a floor-to-ceiling window nearby. This intensifies the perceived cold. My concerns regarding this problem already existed in the run-up to the test. The result is that this situation has to be improved.

A longer conversation with the supplier of my first infrared heating system results in a promising solution: The company has developed very compact, slightly lower power infrared heaters specifically for use in churches. These are primarily used in church pews to warm the feet – which is almost exactly my requirement.

Consequently, I order a 1 x 0.25 m heating panel with 150 W power consumption and install this heater directly under my desk with sufficient distance from my knees. The radiated heat heats the area where my feet usually rest. A combination of a timer and a plug thermostat is used for electrical control. As a result, my new under-table heater only heats during office hours and only until the set target temperature is reached in the ‘footwell’ of my workstation. Excellent!

Because a second IR radiator now heats my office, the large radiator does not start up quite as often. For me personally, the heat distribution is optimal, because my feet are always warm and my head is pleasantly cool. Unfortunately, I could not achieve this with underfloor heating. To get my feet warm enough, I needed the air temperature to be 23 ºC – too warm for a cool head.

My new combination of two infrared heaters results in a much better indoor climate, which I quickly learn to appreciate!

Periodic switching on of the radiator and periodic ventilation

Another concern that I had in advance was the periodic switching on of the radiator. The answer here is simple: Despite the short distance of only 2.8 m and being mounted at head height, the heat radiation from the heating system is not noticeable. I can only tell whether the heating system is on or off when I go to the heating system and hold my hand directly in front of it. That’s why I don’t even notice when and for how long the radiator works during the day. However, it manages to keep the room climate quite constant around the set target temperature. This is important to me and it works without compromise.

Yet the answer to my last question remains unanswered – how does periodic ventilation affect the room temperature in the meantime? However, this is not quite so easy to answer. I have not ascertained any actual figures for answering this question, so I have to answer based on my own subjective feelings. I don’t notice too many differences. If cold outside air enters my office at an air temperature of 5-7 ºC, the temperature quickly drops below the previously reached target temperature. I have the impression that the two infrared heaters cope better with the penetrating cold air than the underfloor heating, where I need 2 degrees more air temperature to feel comfortable. The temperature delta between 23 and 7 is greater than 21 and 7, so I probably feel the cooling effect of the draught more strongly. As mentioned previously, the above description is theoretical and only subjectively evaluated. The difference is not really that big in the end.

In short, here are the answers to the questions I posed before the start of the infrared heating test:

– How does it feel to work in a room heated with radiant heat?
Comfortable. The air doesn’t smell like its coming from a heating system. The environment feels good.

– Would I perceive the air as cooler when using radiant heat? Does that have a positive or negative effect on me?
Yes, I can feel it and I find it pleasant because it helps me to keep a ‘cool head’.

– Would I perceive the furniture and walls to be warmer? Does that have a positive or negative effect on me?
The furniture and the walls are in fact not warmer because I was able to lower the desired temperature of the air by 2 ºC and feel comfortable with it. It saves energy and creates a pleasant working environment for me.

– How does the temperature of the floor change? Do my feet/legs get cold?
Yes, my floor is 4 ºC colder. That was a problem initially. After compensation by a second mini radiator under the table top in proximity to my feet, I found the optimal combination of 21 ºC in the room and 19.5 ºC near my feet.

– Is the temperature drop during and after ventilation stronger or weaker?
The difference is not really big and therefore negligible.

– Can a single infrared radiator heat my office evenly and sufficiently?
Yes, generally speaking, I think that’s possible. In my specific case I needed a second mini radiator for my cold-sensitive feet (problem: a floor-to-ceiling window with poor insulation near my feet).

– What does it feel like having the infrared heater turn on and off periodically? Do I notice that?
No, I notice neither the heating phases nor the radiated heat. There is simply a pleasant and even warmth, without me noticing any disturbing ‘hotspots’.

My conclusion from the infrared heater test: Thoroughly positive

After this extensive personal test, I see infrared heating as a serious alternative to warm water underfloor heating. Irrespective of the operating costs (which I could not take into account in this analysis due to the lack of comparability), the living space’s electrical heating system impresses me with its high practical suitability, comfortable room climate, and individual design options with regard to temperature and appearance. In my opinion, heating an entire building with infrared radiators has become a serious alternative to heat pumps, both for renovations of existing properties and (especially) in new buildings.

This test report is reproduced with the kind permission of the author: Dipl. Ing. (FH) architect Stefan Orth from Bamberg.