Thermostatic Radiator Valve

Thermostatic Radiator Valves (TRVs).

~ unit cost £30 + installation £30 = £60*

On this page


  • Audit
  • Aim
  • Hypothesis


  • Hand tools


  • Thermostatic Radiator Valves (TRVs)
  • Automatic Bypass Valve (ABV)
  • Pipework and lagging


  • Audit
  • Improvements
  • Projects



We’ll look at the common, normative examples.

Improved efficiency and comfort, reducing the need and consumption.


Updating the plumbing can make for a more efficient system. However, simply replacing the boiler may not be enough. Much of the efficiency of the system is in the design and installation of the pipework as well as operable and functional components. The systems need to be fully functional and easy to operate if energy efficiency is to be improved.

A dysfunctional heating system is likely to be difficult to operate and expensive to use leading to inappropriately regulated temperature which impacts on moisture management.

In our older dwellings, the plumbing was most likely fitted long ago and has been modified or added to on numerous occasions. Even a more recent installation is unlikely to have been installed to consider the usability and efficiency of the installation.



Does it work and is it used appropriately?


Establish the nature and condition of the installation.

  • Identify the type of boiler, pipework and the components
  • Engaging and operating the systems
  • Is it operable and functional

What improvements can be made?


The plumbing installed in our homes will have been fitted long ago when our approach to efficiency was very different. It is likely these systems will have been updated or modified at some point. The practicalities of both fitting and amending these systems in an occupied dwelling will have inevitably lead to compromises being made and opportunities to do things better being overlooked.

We take these systems for granted, we engage with new kitchen and bathroom, perhaps new boilers and radiators without questioning the nature of the system behind them. Inevitable without understanding the nature of what we have the opportunity to improve and operate it better is overlooked.


Originally domestic heating and hot water systems were installed to replace the open fires and stoves. Installed into the obsolete fireplace with a gas fire facing the room and a back boiler behind that could centrally heat ‘radiators’ (convection heaters) in other rooms as well as heat a hot water cylinder usually positioned in a cupboard built into the alcove adjacent to the chimney breast in the room above. Early systems, and where gas was not available, a solid fuel stove could also have a back boiler, to heat hot water.

When water is heated it expands, this expansion needs to be accommodated. When the water reaches its boiling point the volume increasing by 1700 times as it changes state from liquid to gas and turns to steam. This is what makes things go bang!

Early heating systems were, therefore ‘open vented’. The boiler, hot water cylinder and the pipework joining these together also connected to a ‘header tank’ located either in the attic or high up above the cylinder. As the hot water expanded the water level in the header tank would rise. Open to the atmosphere as well as with an increase in temperature, evaporation would occur with time. The header tank, fitted with a ‘ball valve’, (like those fitted inside a toilet cistern), would automatically top-up the tank as the level fell,

Pencil, paper, stopwatch and a tacit sense of temperature.


Visual inspection.

Heating: turn on the heating and turn on all of the Thermostatic Radiator Valves (TRV’s)






Thermostatic radiator valves

Thermostatic Radiator Valve

Automatic Bypass Valves


Pipework and lagging


Advice and support








> Vents