You don’t have to have thermostatic Rad valves thoughout the house and I would not recommend you do.
It is just my view but I think the reason Thermostatic Rad Valves are more or less compulsory in British homes is more due to a successful conspiricy of the companies who make, sell and install them, to create more work for the boys, than it is to do with having a good efficient, central heating system.
Do You Ever Turn Your TRVs Down or Off?
Like many of my readers, I am of an age such that I can remember living in homes without TRVs. The radiators were simply on, except for those which were off. They were simple to turn off and this was never a problem.
A few years ago a rule came in that requires heating engineers to fit (or recommend) TRVs whenever a new gas central heating system is installed or even when a new boiler is fitted to an old heating system.
Now, there is a little known get out clause, the customer can put in writing that they do not want TRVs fitted. This clause is there because TRVs will add hundreds of great British pounds to the bill, which some households cannot afford.
What Is Wrong With TRVs?
To me it is obvious. Why put TRVs on almost every radiator in the house? If you wanted to turn that many radiators down or off then you would be better off turning the heating down or off. The TRVs don’t turn the boiler down or off so they do not save on gas bills.
Now, let me qualify my sweeping statements!
Do TRVs Save Money on Heating Bills?
TRVs are good for some rooms and for some homes. They are great for large homes, I mean very large homes, 7 bedrooms, etc. If you have a very huge house with perhaps 3 or more floors and you turn off the TRVs for a substantial part of the house (eg the top floor) this should save you quite a bit of money.
It is all to do with the distance that the hot water will travel along pipes and through radiators before it gets all the way around the system. Of course it is cooling down along the way so in a large house with lots of radiators this can be considerable.
In the UK the vast majority of us live in small homes. Two and three bedroomed houses, terraces, semis and flats. We are mostly quite a squashed up nation. Even our detached homes are only just big enough for us to squeeze into. For most of us in these little homes turning one radiator down or off is going to make little difference to the temperature of the heating fluid when it has made one compete cycle and reached its way back to the boiler.
What Rooms Should Have TRVs & What Rooms Should Not?
TRVs are good if you want the option to sometimes keep a room cooler than the rest of the house. Lets face it. There are not many family homes, flats or appartments in England where we might think about closing dowm a “wing” for the winter.
In my opinion and to suit my (small) home I would say TRVs are suitable for the bedrooms only. We do not “shut off” any of our downstairs space we live fully in the space in our house, as I suspect most families do. As heat rises best to have a nice warm downstairs but cooler bedrooms.
Our oldest son likes his bedroom as cold as possible when he goes to bed. i like my room cold too, whereas Mr Tara Plumbing would like it to be warm or even hot. He knows, however, that he tampers with the heating controls at his peril – the wrath of Mrs TP!
Mrs Tara Plumbing 
PLease don’t baffle the experts by using common sense – but you’re right of course. I believe that TRVs dont really control room temperatures, just radiator temperatures. The thermal contact of the thermostat, connected to the radiator by a copper pipe, must be better than the thermal contact to the air in the room. And someone else must have had this thought when air slots started appearing in the TRVs. Room to room temperature balance could be achieved just by simple flow control valves. If a window is opened in the room it will get colder, with or without a TRV. The house thermostat is the only one that turns the boiler on and off to regulate temperature.
Two other thermal facts for you:
Condensing boilers are claimed to waste less than half the heat of conventional boilers. This is true in ideal conditions; in reality, when reboilering an existing sytem, maintaining the return water temperature at a high enough to properly heat the house will reduce the efficiency. And the fuel cost benefit to the user is not the factor two ration of waste heats (typically about 15%/25%=0.60), but the much lower ratio of efficiencies (75%/85%=0.88). Condensing boilers are still a good idea for new installations though, and their lower reliability provides more employment opportunities for plumbers.
Adding another foot of loft insulation to an existing 3 or 4 inches saves very little – the 3 or 4 inches already reduces ceiling heat losses by only a small amount compared with other losses from a room.
I’m not a plumber, but I am a physicist (DPhil) so I understand the principles and the sums.
OOO I love this sort of conversation.
But then I do rather love physics and maths…
Tell me some more.
May I add I think the point you make is very important – TRVs do not turn the boiler off but a room thermostat does.
Some one talking sense at last!! Turning down a radiator doesnt turn down the gas flame. That stays on longer, and works harder, because the room temperature will never match that set by the room thermostat. It certainly isnt like a gas ring, where you can turn it down to a simmer Your just getting LESS HEAT for the SAME MONEY. .
I don’t think that is exactly true.
I’ve looked in to this a lot more since writing this post and certainly you would save a little money by turning a TRV off but questionable how much and how often most people would want to do that if they fully occupy their house. In our house we live in every room of our house. I like the heating off upstairs but would never need to turn off the heating in some of my ground floor rooms so why have TRVs there.
TRVs are a rip-off – just a glorified rad valve with numbers on to help people know how far to open the valve – but you pay 10x the price of a budget old-school rad valve