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Radiator free Europe: understanding the world of heating efficiency

Radiator free Europe: understanding the world of heating efficiency

Warning! Efficient central heating controls are excruciatingly interesting!

Proper configuration of central heating controls is one of the biggest green improvements anyone can make to a home. For many households, it doesn’t even require that much, if any, money.

Whether gas, LPG or oil-fired, any central heating system can be optimised by equipping it with a room thermostat, a timer and thermostatic radiator valves (TRVs).

Flowchart showing how central heating controls work.
Optimised central heating systems efficiently maintain a comfortable temperature throughout the house. Click on the image to enlarge.

The combined effect of these central heating controls can be a 40% reduction in energy usage from heating. Considering that heating accounts for roughly half a household’s energy usage, the savings could be enormous.

But because the world of central heating controls is so mind-numbingly dull, people seldom configure them such as to optimise their efficiency.

How can a household make a uniquely monumental difference to their heating efficiency? Read on.


Firstly, the following only considers room heating as opposed to running hot water.

Secondly, The following heating controls are gradually being phased out in favour of smart heating technology, i.e.: devices that use artificial intelligence to efficiently heat a building’s interior. Watch this space for info on smart heating controls.

Nonetheless, the classic technology is still in wide availability and can make vast reductions to energy consumption when properly applied.

Even in the absence of any heating controls, it is not necessary to upgrade the boiler unless it is suitably old. In such case it is probably a good idea to replace the appliance with a new, more efficient model. The same applies for thermostats and radiators.

Lies, damned lies and room thermostatistics

A room thermostat is a small capsule connected to a boiler.

Central heating controls crucially include room thermostats.
A room thermostat looks something like this.

It is not always obvious the thermostat is connected to the boiler as connections are often wireless.

The thermostat’s job is to monitor the temperature of the room in which it is located and control the heating so as to maintain a comfortable temperature, usually between 18℃ and 21℃.

So, when the temperature of the room matches that set on the thermostat, the heating switches off. When the temperature of the room is lower than the desired temperature, the heating switches on.

Even on a cold winter’s day, the thermostat needn’t be touched. The heating will adjust accordingly. It just may take longer to warm up to the desired temperature.

Of course, insulated homes will heat up far quicker and retain the heat for much longer.

The underlying physics of thermostats is the staunch Victorian technology of thermistors – electrical components across which the current depends on the temperature. And you thought heating couldn’t get any more fascinating.

Meanwhile, smart heating technology uses a geekathon of twenty-first century data analytics and artificial intelligence. For this reason, they are far more efficient and easy to use.

A room thermostat does not necessarily maintain a constant temperature throughout the entire house, though. In fact, it rarely does, as each room in the building loses heat at a different rate.

The solution to this problem comes with thermostatic radiator valves (TRVs), which act as independent thermostats for each individual radiator in the house.

TRV show: what are thermostatic radiator valves?

Thermostatic radiator valves (TRVs) maintain a constant temperature in the room, as specified on a standard dial that reads from 1-5.

TRVs are a great way to control central heating.
TRVs have similar temperature dials to regular radiators.

The maximum temperature the radiator will ever reach is that specified on the central room thermostat.

Integrated into the TRV is a mechanism consisting of a pin and a spring filled with either a liquid or a wax.

At close to comfortable temperatures, the substance expands, pushing the pin further into the valve which restricts how much water can enter the radiator, thus restricting how much hotter it can get.

The opposite happens at colder temperatures, i.e.: full water flow occurs. Generally, liquid-based TRVs are better as they are quicker to respond to temperature changes.

As with room thermostats, this innovative mechanism is rather out-dated, with most favouring smart TRVs. The outstanding feature of smart TRVs is remote control.

That is not to say, however, that classic TRVs are obsolete.

The room temperature capping technology of TRVs means that excess heat doesn’t supply rooms that do not need it.

Perhaps some rooms reach a comfortable temperature quicker than that containing the central thermostat. TRVs mean that some radiators will switch off before the boiler.

But for all the energy they will save, there are a number of practicalities that must accompany installation of TRVs.

TRV no-show: Where should you not install TRVs?

Having a TRV in the same room as the central thermostat, for instance, is pointless.

In fact, deciding where to install a thermostat and TRVs is very important.

The TRVs will be redundant if the rooms they are in heat up more slowly than the environment containing the central thermostat, as the boiler will switch off before other rooms in the home reach a comfortable temperature.

The other way around, however, will mean that TRVs can switch off individual radiators without affecting other rooms in the home.

Using radiator covers with TRVs gives a misrepresentation of the temperature of the room, meaning that the TRV could switch the radiator off when the rest of the room is still below a comfortable temperature.

Funny picture of an obstruction to central heating control.
Radiator obstructions create TRV malfunctions.

The converse of placing TRVs underneath a radiator cover is placing it near a draught. The TRV will measure a different temperature to the overall temperature of the room, meaning it can be needlessly letting a radiator heat up.

The absolute no-no with regards to TRVs, though, is in bathrooms.

Bad steam: why should you not install TRVs in a bathroom?

If someone were to take a bath or shower, steam would cause a TRV to switch the radiator off.

The problem? When steam meets a cold surface – windows, bathroom mirrors etc. – as would happen when the bathroom radiator is off, it quickly turns into condensation which is how black mould forms.

Instead, if the radiator is on during bath time, the windows and mirror will be warm when the steam reaches them. This means that condensation will form to a less severe extent.

This is serious, as the health implications of black mould are ugly. See ‘damp duty: health risks from damp and mould’ in this article for the details.

Good plumbers tend to advise best practice regarding TRVs and will not fit them to bathroom radiators.

Who kills the radiator star: common problems with TRVs

The most common problem with TRVs is valve sticking.

The result is that twisting the temperature gauge has no effect. This is a quick fix: the valve will stop sticking with the application of some oil on the pin after removing the valve head.

If this doesn’t do the job, specialist assistance is needed.

Furthermore, complaints about TRVs not coordinating well with a central thermostat are common.

Usually, this is due to TRVs being in rooms that don’t heat up as quickly as the environment in which the central thermostat is located. This, then, diagnoses the fundamental problem of poor home insulation, which needs addressing more immediately.

Happily, a lot of TRV problems can be solved with smart controls.

Smart TRVs, for instance, learn heating patterns and will auto-adjust depending on the time of day. They can even predict when people will enter a room, so will learn to only allow water to flow to the radiator at certain times.

Unfortunately for the classic TRVers, spare parts will become less standard with such a thriving smart technology market, despite the conventional devices still offering effective service.

Time is money: effective use of timers

Timers on home thermostats are standard. Using them is key in the quest to reduce household energy consumption through heating by 40%. However, many people find the sight of digits and dials too daunting to touch.

Flowchart showing how central heating controls work.
Using a timer optimises a central heating system’s efficiency. Click the image to enlarge.

Setting a timer, aka programmer, on the thermostat means that it only controls the temperature at certain times of day. There is no need, for example, to maintain a comfortable living temperature when there is no one at home.

To set the timer, it is best to consider the so-called warm-up and cool-down times, i.e.: the times it takes the coldest room in the home to heat up to a comfortable temperature, and to cool down to an uncomfortable temperature respectively.

So: if the warm up time is 30 minutes and the cool down time is 15 minutes, have the thermostat set to switch off 15 minutes before the home is empty and switch on 30 minutes before people return from work/lectures/church/fishin’/gallivanting around town.

Of course, life is too short to set heating controls to absolute precision or to fiddle with the thermostat every time the household incurs a minor change in routine.

Timers can, therefore, be manually overridden at the press of a button.

Smart thermostats, however, can do better.

Using artificial intelligence, they can learn routines to greater precision. They can calculate warm-up and cool-down times depending on the weather. They can even sense when people are in the home.

Money and carbon savings

Energy Savings Trust estimate that households can save £75 and 320 kg of CO2 annually by turning the thermostat down by a trifling degree centigrade.

The EST also figures that implementing TRVs and a timer will save a further £60 and 310 kg of CO2.

630 kg of CO2 in total may sound like a lot to save, but it is dwarfed by the 5.6 million tonnes of CO2 emitted by agricultural processes in the UK every year.

Nonetheless, to neutralise the colossal carbon footprint of agriculture, it would require less than a third of UK households to make their heating more efficient.

Mass, collective action really can make a remarkable difference.

The costs of central heating controls

It is highly unlikely a home does not already have a programmable room thermostat. If not, there are a number of things to consider.

Whilst boilers do have their own thermostats that regulate the hot water temperature, they are very inefficient for regulating room temperature.

Instead, it is best to buy a room thermostat. Costs are between £100 and £200, whilst smart thermostats cost slightly more.

Knowledge and experience of plumbing can make installing a new thermostat a fairly trivial task. Otherwise, a professional needs to do the work.

Secondly, a home with a boiler but no thermostat probably means the boiler is very old and inefficient. In this case, it is likely that a new boiler should be fitted. A plumber will offer the best advice.

As for TRVs, a pair costs between £20 and £30. Self-installation is possible, but only with a degree of plumbing knowledge and experience as the procedure involves cutting around copper pipes.

Moreover, to kit an entire house out with TRVs, the pipework may need to be drained. Only professionals can make this call. Likely to be day’s work, the cost of doing so is around £250.

For just a single radiator, plumbers usually just freeze the pipework, which costs about £100 for what is typically half a day’s work.

Another cost to consider is that of a heat survey at about £200.

This identifies the regions of the house losing and retaining the most heat. As TRVs are only appropriate for well insulated zones, a heating survey can save money in the long run.

Naturally, heating surveys can also diagnose the more acute issues of poor insulation. In such cases, consider installing cavity wall or loft insulation.

Merchants of menace: dubious sellers of central heating controls

The biggest name in the business is arguably Honeywell, the multi-tech giant.

They shift batches of everything from the most primitive TRVs to state of the art smart heating control systems. Their thermostats and TRVs get very good reviews across the board.

And that concludes the good news. Honeywell’s customer service acquires mostly ‘bad’ reviews, citing poor telephone service and advice. Some customers have even complained of dishonoured warranties.

Danfoss is also a big name in thermostatic technology. They have an almost identical reputation to Honeywell, with fairly good reviews on the products but poor performance in the customer service department.

Both companies are seemingly committed to a green future.

Danfoss, for instance, are heavily involved in reducing the environmental impact of transport (particularly by joining the Zero-emission truck coalition, an initiative to reduce the emissions of the USA’s renowned trucking sector to net zero).

Nevertheless, Danfoss continue to sell drilling, extraction, refinery and infrastructure components to oil and gas companies.

Meanwhile, Honeywell audaciously boasts their involvement in greening up the transport and building sectors, whilst simultaneously celebrating their ten-year contract with the Abu Dhabi National Oil Company (ADNOC).

Mixed messages from Honeywell and Danfoss.

Oily wake-up call: controversy amongst heating giants

For context, ADNOC enjoys a daily output of 3 million barrels of crude oil and 10.5 billion cubic metres of natural gas.

A Guardian investigation revealed ADNOC as one of a mere 20 companies responsible for a third of all global CO2 emissions, itself having released 13.84bn tonnes since 1965.

ADNOC are certainly not amongst those big oil companies saving their reputations by investing colossal amounts into renewables.

Citing the changing landscape in global oil consumption, ADNOC’s 2030 energy plan hopes to extract every last penny from each barrel of oil and increase their profitability.

An industry on its way out… to the bank.

Honeywell will assist this mission by providing artificial intelligence (AI) asset monitoring and predictive analytics solutions. 

Of course a prediction that doesn’t need AI outsourcing is that use of oil will continue to cause sharp rises in global temperatures.

Buying heating controls from Honeywell and Danfoss are not the greenest options. Thankfully, there are some alternatives.

Warmers’ market: reputable sellers of central heating controls

Vaillant is a big name around the world, exclusively involved in the heating industry. Most notably they manufacture boilers, with a current focus on appliances that run on renewable energy means.

Generally, their thermostats have fairly good reviews. Unlike Honeywell and Danfoss, however, their customer service scores excellent reviews across the board. The price to pay is slightly more dear than their Honeywell and Danfoss counterparts.

As for TRVs, Drayton and West Radiator’s Realm line of TRVs routinely win appraisal from review sites as the best mid-range gizmos. Both companies specialise in radiator valves.

An up-to-date review of the best TRVs on the market can be found here.

However, Drayton is a subsidiary of Schneider Electric. Whilst the multi-technological company complies with ISO 14001 environmental standards, they have ties to – yep, you guessed it – big oil. 

It is seemingly predictable that many of the manufacturers of household heating controls also have ominous connections to the oil and gas industry. Unsurprising, given that that’s where the money has been in tech for years.

Future leaders in heating are likely to be the 21st Century data giants – Google, Samsung and Amazon, to name a few.

For now, Vaillaint is a reliable option for room thermostats. As for TRVs, West Radiator is the safest option guaranteeing quality, with no clear attachment to a dubious record.

Clubbing together

Given how few households have TRVs installed, it makes sense to club together on them. The opportunity to install TRVs into every home in a local carbon club is likely to be attractive work for local heating engineers.

The reward could be a discounted price per person, as well as the ability to share knowledge of faults and best practice.

Additionally, proclaimed DIY experts can purchase self-install TRVs from the Don’t do a Dodo national club.

What would the dodo do?

No thermostat, no temperature controls, no timers. Just a prehistoric boiler pumping out Saharan heat 24/7 throughout the dodo’s severely under-insulated house, if it were alive today. Don’t do that.


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