• £0.00
  • info@castrads.com
  • Call 0161 439 9350
  • Coronavirus latest: We are open. Read more here.

How to heat efficiently

Home / Inspiration / How to Heat / How to heat efficiently

Sustainable heating and energy saving

How to heat efficiently

Full disclosure - when it comes to efficiency, the type of heat emitter you choose doesn’t make a huge difference. 

Unlike your boiler or light bulbs, your radiator doesn't change energy from one type to another. Your boiler changes gas into heat, a light bulb changes electricity into light. So you can measure how efficient it is at that conversion. But with radiators, the energy your boiler puts in is emitted into your home. 

So, technically speaking, a radiator is a radiator, although some are better built, longer lasting and infinitely better looking than others...

Sleek cast iron radiator in natural pewter finish on dark background.
Neptune 24in in Natural Pewter with Natural Pewter Windsor TRV and Whitworth wall stays.


If you think of a building as a whole system, factors such as insulation, boiler maintenance and add-ons like TRVs and a learning thermostat are where the meaningful energy savings are to be made. Here's our advice.

Think smallThink small icon

In a historic house (pre 1919), unless you’re undertaking significant refurbishments like the clients in our case studies here and here, the experts tend to advise taking care of the smaller, cheaper modifications first, before making bigger changes to the fabric of the building such as new windows or exterior insulation.

In this article, Annette Lamley from the Centre for Sustainable Energy suggests draught-excluders, floor coverings, heavy curtains and loft insulation as the most cost-effective additions. Another very simple change is to swap out old radiator valves for TRVs

Radiator valves.


Our TRVs can easily be fitted to existing radiators with options for steam and hot water, putting you in control of your heating.

Without the need to overhaul your whole system or scrap any original radiators, this quick fix reduces your energy consumption and creates a comfortable temperature throughout your home.

One-pipe steam thermostatic radiator valve on polished cast iron radiator
Niva one-pipe steam TRV in Chrome on Neptune 20in Full Polished cast iron radiator.


Managing the system with a learning thermostat such as Nest means even greater energy savings. In a study spanning 41 states, the Nest Thermostat saved an average of 10-12% on heating and 15% on cooling.

Heat cleanheat clean icon

As water travels around a hydronic system it deposits a mixture of iron oxide, contaminants and metal debris caused during installation. Over time, this ‘sludge’ builds up in the pipes and the radiators themselves.   

Sentinel show that running a dirty system reduces water flow and overall efficiency by around 15%. Sludge sitting at the bottom of a radiator creates cold spots and also generates hydrogen gas which stops them from heating up properly unless they’re constantly being bled.

It may eventually lead to pitting and corrosion which causes pinhole leaks and rusting.

Group of Sentinel products for keeping a clean and efficient heating system.

A system can be easily cleaned by flushing the sludge through, draining it out and refilling with clean water. Adding a chemical inhibitor to the water will help to reduce further build ups of sludge. Fitting a magnetic filter, along with regular servicing, will protect the boiler from damage and ultimately extend its lifespan. We recommend Sentinel products for all aspects of hydronic system care.

Go greenGreen leaf illustration

As the engine of your home heating system, your boiler determines its overall efficiency. Using less energy to generate heat in the first place, cuts your consumption considerably.

A modern condensing boiler uses a heat exchanger to recuperate heat from the return pipe and can run at up to 90% efficiency provided the temperatures are set correctly. Hydronic central heating should operate at about 70C and hot water at 60C to get the best out of a condensing boiler.

Boiler with maze of pipework.

A biomass boiler which burns logs or wood pellets to generate heat, similarly operates at 90% efficiency but has the additional benefit of using sustainable fuel, so also cuts CO2 emissions by 90% compared to fossil fuels. Read our case study on Underscar Manor for a real-life example of cast iron radaitors running on biomass.

The ultimate eco-friendly solution for running a central heating system is the heat pump. Both air and ground source heat pumps are extremely efficient, generating around 3KW of heat for every 1KW of electrical energy put in. They also have the lowest environmental impact given that they utilise latent heat energy in the air and in the Earth. 

With a heat pump, you can set the flow temperature very low and still comfortably heat the house. Writing for YouGen.co.uk, alternative energy expert John Lightfoot explains, "The lower this set point, the more efficient your heat pump will be, and therefore the cheaper to run. However, the lower the water temperature, the more radiating surface area you need to emit the same amount of heat.”

He adds, "You will hear many people referring to over-sizing the radiators for heat pumps. I prefer to use the more appropriate term, right-sizing the radiators. If the radiator is sized correctly it will provide the heat you require."

Country house in Wales UK.
This refurbished farmhouse in Wales, UK uses an air source heat pump.


"You will often hear that underfloor heating should be the only type of heat emitter you consider when using heat pumps. The fact that underfloor system can work very well with flow temperatures as low as 95F do make them an ideal partner for heat pumps. If, however, you have an old property it may be impractical to install an underfloor heating system, and in many cases correctly sized radiators are the only practical option."

Our radiators are priced so that the section cost falls the more you need.