Five-minute Guide to… Heat­ing Con­trols

The tech­nol­ogy for con­trol­ling the heat­ing in our homes is ad­vanc­ing rapidly, says en­ergy ef­fi­ciency expert Tim Pullen

Homebuilding & Renovating - - Contents - Tim Home­build­ing Ren­o­vat­ing’s is & expert in sus­tain­able build­ing and en­ergy ef­fi­ciency. He is the au­thor of Sim­ply Sus­tain­able Homes. Tim Pullen

109 The tech­nol­ogy for con­trol­ling cen­tral heat­ing in our homes is ad­vanc­ing rapidly. En­ergy-ef­fi­ciency expert Tim Pullen ex­plains what’s new and the po­ten­tial cost sav­ings to be made

For had fairly as heat­ing long crude, as con­trols. es­sen­tially we have had Ad­mit­tedly deal­ing cen­tral with heat­ing these the used tem­pera- we to have be ture of the whole house from a sin­gle ther­mo­stat. The last few years has seen a rapid de­vel­op­ment in con­trol tech­nol­ogy, which can make a sig­nif­i­cant dif­fer­ence to ac­cu­racy, ef­fi­ciency and, ul­ti­mately, to the heat­ing bill. And as is so of­ten the case, there is now a plethora of choice and it is dif­fi­cult to know what is best.

Set­ting the Pa­ram­e­ters

A combi boiler, much loved by the prop­erty de­vel­oper, will use just a sin­gle timer or pro­gram­mer, as water is heated as re­quired. There are se­ri­ous ques­tion marks over whether this is a good idea for the home­owner as it of­fers the bare min­i­mum level of con­trol.

Sim­i­larly, a sim­ple in­di­rect hot water cylin­der will have a ther­mo­stat fixed to the cylin­der to mea­sure the tem­per­a­ture im­pli­ca­tion all will the be of water at the the water of in same this the in cylin­der tem­per- is it. that The ature to heat and it the un­til boiler the will de­sired run tem­per­a­ture is reached. A ther­mal store of­fers far more con­trol as it will store water at a range of tem­per­a­tures. If we have un­der­floor heat­ing we want water at around 40°C but we also want do­mes­tic hot water at 64°C to kill le­gionella bac­te­ria. The con­trols in­her­ent in a ther­mal store al­low us to do that without wast­ing en­ergy.

The Fall of TRVS

The old-style ana­logue room ther­mo­stat is still be­ing in­stalled, usu­ally one to each floor. At best, these are ac­cu­rate to +/-2°C — poorer qual­ity ones can double that in­ac­cu­racy. To­gether with a pro­gram­mer that al­lows the heat­ing to be switched on and off mul­ti­ple times each day, and to deal with hot water sep­a­rately, this is a bet­ter op­tion than

“The last few years have seen a rapid de­vel­op­ment in con­trol tech­nol­ogy”

“Es­ti­mates on the sav­ings that zone con­trol can give vary — some put it as high as 20%”

a combi boiler, but by not much. More com­mon now are ther­mo­static ra­di­a­tor valves (TRVS). These are, as the name sug­gests, fit­ted to the ra­di­a­tor, with grad­u­a­tion typ­i­cally from one to six. They give no in­di­ca­tion of the ac­tual tem­per­a­ture in the room, be­yond com­fort­able or un­com­fort­able. These were de rigueur for a few years but have, thank­fully, fallen out of favour.

The big change in the past few years has been the re­al­i­sa­tion that dif­fer­ent rooms need dif­fer­ent tem­per­a­tures at dif­fer­ent times, of­ten re­ferred to as zone con­trol.

The Rise of Zone Con­trol

Zone con­trol ac­tu­ally means con­trol­ling the heat­ing in each room, and it can be done in one of two ways: cen­trally or individually.

An un­der­floor heat­ing sys­tem will be con­trolled cen­trally, with a ther­mo­stat in each room re­port­ing back to the cen­tral pro­gram­mer where the home­owner sets the time and tem­per­a­ture for each room.

For ra­di­a­tor sys­tems a sim­i­lar level of con­trol comes via pro­gram­mable ra­di­a­tor ther­mostats. These are bat­tery pow­ered and al­low for pre­cise con­trol of the time and tem­per­a­ture in each room. They are fit­ted like TRVS and some sim­ply re­place the body of a pre-ex­ist­ing TRV so that the heat­ing sys­tem does not have to be drained down. There are also wire­less op­tions that can be pro­grammed from a cen­tral point, oth­er­wise each ther­mo­stat has to be pro­grammed individually.

Re­mote Heat­ing Con­trols

The emer­gence of re­mote heat­ing con­trols has been gain­ing a lot of press cov­er­age in the last cou­ple of years. A phone app al­lows the user to change the tem­per­a­ture or tim­ing of the heat­ing and/or hot water sys­tem from wher­ever they hap­pen to be.

The one we have all heard of is the Hive Ac­tive Heat­ing con­trol, mar­keted by Bri­tish Gas, but there are many oth­ers: Heat­miser, Tado, Nest, to name a few. Some, like the Nest and Tado, are said to be in­tel­li­gent in that they learn the user’s habits and au­to­mat­i­cally change their set­tings to meet pre­vail­ing con­di­tions — they can ap­par­ently de­tect that the home­owner is not in the house and will de­lay switch­ing the heat­ing on, or turn it off.

These sys­tems have a de­vice in the house that con­nects to the ex­ist­ing con­trol sys­tem, which is ac­cessed via a phone app. The think­ing is that if the user has a ‘ busy’ life­style (that is, a propen­sity to go some­where other than home af­ter work) then the app will al­low them to ad­just the heat­ing ac­cord­ingly. There are sig­nif­i­cant claims made there trolling are for the these ap­pli­ca­tions heat­ing de­vices, in where a like hol­i­day ‘sav­ings this home. could of £150 So be far true, per the year’ like En­ergy con- and Sav­ing Trust has been un­able to con­firm how ac­cu­rate those claims are. The Hive de­vice has so far proved the most pop­u­lar with more than 100,000 units sold. This sounds like a lot, but there are around 22 mil­lion homes in the UK so there is still a large mar­ket to work on.

Bri­tish Gas re­cently con­ducted a sur­vey of 2,000 users and more than 70% said they had saved money af­ter hav­ing the gadget in­stalled. To put it an­other way, up to 30% (or 30,000 peo­ple from the to­tal 100,000 units sold) may have wasted their money.

Cost and Po­ten­tial Sav­ings

The cost of a zone con­trol sys­tem for an un­der­floor heat­ing sys­tem will, of course, vary with the size of the house and the man­u­fac­turer. Bud­get £1,000 to £2,000 for an in­stalled sys­tem. Pro­gram­mable ra­di­a­tor ther­mostats will cost £20 to £30 each, plus in­stal­la­tion. The wire­less op­tion will add £200 to £300 to the bill. The re­mote con­trol sys­tem will cost from zero (the Nest de­vice is free to Npower cus­tomers) to around £300, in­clud­ing in­stal­la­tion. The Hive de­vice is £199.

Es­ti­mates on the sav­ings that zone con­trol can give vary — some put it as high as 20%. When you think that a bed­room will prob­a­bly only need heat­ing for one to two hours per day, while the liv­ing room and kitchen may need heat­ing for eight hours or more, you can see where those es­ti­mates come from.


Be­ing in con­trol of your heat­ing sys­tem is a good thing, and more con­trol is un­doubt­edly a bet­ter thing. Well-in­su­lated homes al­low the sys­tem to bring the house to the de­sired tem­per­a­ture, within less than 1°C, and keep it there. Con­trols also al­low rooms not cur­rently be­ing used to be treated dif­fer­ently. But bear in mind that which­ever con­trol sys­tem you use, it needs the home to be well-in­su­lated to be re­ally ef­fec­tive.

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