heat-policy

Following some public discussions, and media requests I’ve developed some thoughts on infrared heating and considered what it is, and why it’s unlikely to be an important future heating technology.

What is infrared heating?

IR heating emits infrared radiation and differs to what most of use have in our homes where we have radiators, so called convector heating which heats the air and then heats up the building and our bodies. Infrared radiation isn’t absorbed well by the air and so it directly heats objects, effectively leaving the air cold (although the warm objects do themselves give off heat and can then heat the air and the space that way). You can get gas fired IR heating and I found this article which was based on gas IR heating but notably is about heating a warehouse where you’d never be able to heat the whole space.

I’m talking about electric infrared heating. With this technology, an electric charge passes through a material and the material emits infrared radiation (some is also emitted as convection as the panels do themselves get hot). We have all seen these before with halogen heaters being a good basic example where much of the heat output is radiated. Specifically, much of the recent focus is on ‘far infrared’ heaters, those where the emitter doesn’t get too hot and the majority of heat is emitted as IR. The maximum efficiency of electric IR heating, just like electric convection is 100%.

What are the possible benefits?

IR heating is just a type of resistive heating i.e. a substance resists an electric current and emits radiation. In an electric convection radiator the air is heated. In an IR panel the heat is (mostly) emitted as infrared radiation. The main argument seems to be that IR heating needs less energy overall because you only heat the things which need heating such as bodies.

What are the issues?

By reducing the overall heat demand of a building and targeting only certain items, while you may use less energy, overall the building will be colder than if you maintained a constant air temperature. As a result, damp and mould will be more common and the general advice against damp is to keep your house warmer (see here: https://www.cse.org.uk/advice/advice-and-support/damp-condensation). It is possible that you could have IR heating that gets to all walls but in real life sofas and furniture will be in the way, basically you end up with heat shadows. And if you are heating all the walls, again this defeats the object of only heating bodies. You might as well use basic electric heaters.

There can also be significant comfort issues associated with infrared heating although actual research is limited. In general, only things which are hit by the IR radiation will get hot although some heat will be emitted by the things which get hot and heat up the surroundings (effectively negating the benefit of the direct heating). I shared this example of very bad (illegal?) advertising on twitter and got this response which basically explains my concerns about directional heat and also explains why I once had cold legs under a table in a restaurant heated with IR heaters on the ceiling:

So why heat pumps?

Heat pumps are indeed more expensive to install than resistive heating but you get the value from the fact that for each unit of electricity, you get 3 or 4 units of heat. This is factored into the models and analysis that I base my thinking on and that overall makes heat pumps look like a cheaper and more deliverable option. It is also worth adding that with resistive heating, because you don’t get the heat pump value of 3 out from 1 in, as a result, you would need a far larger electricity system i.e. bigger wires and more power stations to fuel it.

Finally, on a carbon perspective, again the heat pump uplift is significant. In resistive heating because of the 100% efficiency if your electricity carbon intensity was 200gCO2/KWh your electricity carbon intensity would be 200 gCO2/KWh. The heat pumps performance effectively reduces the carbon intensity of heat to a 3rd or a quarter i.e 50 to 67gCO2/KWh.

In some analysis shared with me: a Stuttgart study effectively shows that the total efficiency of the IR panel is around 100%, no surprises. A second report was very vague and built on Wikipedia references. It assumed gas prices and electricity prices would converge in 2024 (currently a factor of 4 difference). It also admitted that it couldn’t provide fair comparisons because it was a very time limited study.

Finally a 3rd simulation based report was based on an extremely efficient building. A similar size to my (EPC B) house but with even lover heat demand (by around 40%) so this is a very very efficient house. As such the overall heat demand is low and so the cheap running costs of a heat pump are outweighed by the cheap capital costs of the IR heater. Also worth noting is the fact that in the study, the whole house was kept at a temperature above 21 degrees i.e. the IR heating was not used to heat bodies but the whole house.

Overall, I’ve seen no evidence that IR heating is likely to be an important strategic option, despite some in the industry trying to convince me otherwise.

What about hot water?

Hot water is a significant demand for most houses and IR heating doesn’t provide this whereas a heat pump can, efficiently. This issue cannot be ignored. As such it would be fairer to compare IR heating to air to air heat pumps (i.e. air conditioning where hot water systems are not used but air is blown). This are significantly cheaper than a typical heat pump which will do your radiators and your hot water. I just found a quote for £2250 for a 3.5KW air con unit (fitted) which will also do heating with the efficiency of a normal heat pump (possibly better).

My concerns?

As indicated by my previous tweet, there is a real concern that IR heating is miss-sold to people as cheap when they are just spruced up old technology. My searches on Google highlighted this consumer issue.

Some housebuilders seem to be latching on to the idea of these as they are cheap to install but have high running costs relative to heat pumps. There is specific mention of this issue in the future homes standard consultation as the government is worried that running costs will be ignored by housebuilders and so a metric on running costs is being considered (something I strongly supported): see p28 https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/852605/Future_Homes_Standard_2019_Consultation.pdf. This is a REALLY huge issue to watch, knowing the historical influence of the large housebuilders.

Summarising

Some UK BEIS analysis considered electric heating options. This quote is particularly telling on IR heating.

‘NEA recommends that infrared heaters are installed only into well-insulated homes and are avoided where residents are at risk of fuel poverty. They also note that infrared heaters are more suitable for dwellings which do not need to be continually heated.’

So, IR heating. Good for inefficient spaces that need to be heated occasionally but not good for continuous heating of buildings.