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How to Heat: An Eco-Home

Topics: Efficiency, renewable energy and heat loss calculations.

Forget ultra-modernist zero-carbon cubes and Hobbit-style earthships, the real eco-home revolution is quietly happening inside existing homes.

Retrofitting older houses cuts carbon emissions, saves on building waste and preserves part of our architectural history.

As part of an eco-friendly refurb, cast-iron radiators offer an unbeatable lifespan, high-tech, efficiency-boosting controls and the option of reusing salvaged originals.

They’re also an ideal partner for renewable energy sources.

Home heating hurdles

Efficiency - Waste not, want not

Eco homes are about taking a holistic view of the entire house. For instance, taking measures to curb heat loss will in turn reduce the amount of heat required. So it all begins with insulation.

With a central heating system, energy consumption is determined by the heat source as opposed to the heat emitter. Whether that source is a boiler or an alternative system, regular maintenance and servicing is crucial to ensure optimal efficiency.

Radiator valves have made huge, high-tech advances in the past 50 years that do all the heavy-lifting in terms of saving energy.

Florence 3 Column in Little Greene Cordoba with Niva Antique Brass
Florence 3 Column in Little Greene Cordoba with Niva Antique Brass

Thermostatic Radiator Valves (TRVs) are a simple, mechanical solution to limit energy wastage. Genius Smart valves offer even greater efficiency and can be controlled remotely.

Connecting everything via a learning thermostat such as Nest is proven to make significant energy savings by tailoring your heating system to your home’s specific needs.

Running on renewables

Running on renewables

Just because cast-iron radiators were born in the coal-fired Victorian era does not mean they are stuck there. All of our models are compatible with renewable energy sources.

In fact, air and ground source heat pumps produce low-frequency heat cycles in a very similar way to the coal boilers that cast-iron radiators were originally designed for - both are slow to warm up and slow to cool down.

The features that made them run well on coal - their high thermal mass and high water content - make them equally well suited to the slower heat cycles and lower water temperatures of a heat pump.

The case study below uses an air source heat pump. Read How to heat a British country house to find out how Underscar Manor runs its cast iron radiators on a biomass boiler.

Heat calculations - Ask the experts

There’s nothing standard about an eco home.

Greening a conventional house involves a unique combination of measures for each individual property. In short, black box online heat calculations will not give you accurate measurements for such a particular project. It is vital to get expert advice by booking a site visit with our team.

Longevity - Built for the future

One of the biggest advantages of choosing cast iron is longevity. While steel panel radiators are designed to last between 10 and 20 years, ours have a lifespan of at least 100 years.

Longevity, Built for the future

Their modular construction also means that, in the rare event of a fault, the unit can be repaired, replacing a single section instead of throwing out the whole thing.

With our refurbishment service we are even able to restore century-old original radiators, giving them a new lease of life for the next 100 years.

Case study - Powys, Wales


The house - Lower Glasnant, a stone farmhouse in the Welsh Marches thought to date from around 1820. It is surrounded by 20 acres of forest and extensive open moorland beyond.

The project - Substantial interior refurbishment to the existing house for use as a holiday let and conversion of adjacent cottage and outbuildings into additional guest accommodation. The aim was to create a luxurious retreat with a low environmental impact, in harmony with the property’s woodland setting.

Mercury 4C by Castrads
View of the semi-wild garden area from the cottage bedroom.
Mercury 4C 760mm in Pewter
View of main house from cottage bedroom. Bed by Camerich, mid-century sideboard from The Old Electric Shop in Hay-on-Wye, Mercury 4 Column 760mm in Pewter by Castrads.

Remodelling existing housing stock, even if it’s older, is one of the greenest options for creating an eco house, dramatically saving on resources, materials and building waste. While the age of a house is a major factor in gauging its energy efficiency, improvements such as adding insulation board to interior walls, relaying or recovering floors, renewing doors and windows will significantly improve energy loss from an older home.  It is even possible to bring it up to Passivhaus standards without the resource consumption associated with a new build. Take a look at these retrofitted Victorian houses that achieved Passivhaus status in Chorlton, Manchester.

Refurbishments to Lower Glasnant included adding compressed foil insulation

Refurbishments to Lower Glasnant included adding compressed foil insulation, relaying all floors with engineered wood and new doors and windows from local company Guy James Joinery.

Lower Glasnant runs on an air source heat pump. This renewable system uses an evaporator coil to extract heat from the outside air and boost it to the desired temperature. Heat energy is then transferred to a conventional hot water and heating circuit.
A heat pump works more efficiently at a lower flow temperature so it requires radiators with a larger surface area.

Column radiator in open-plan country kitchen

So radiators running on a heat pump do need to be bigger than those on a conventional boiler. But by heating Lower Glasnant with cast-iron, the clients achieved the larger surface area with radiators that take up only 10% more wall space than the oil-fired steel panels they had before.

We recommended a large Grace 4C 960mm at 24 sections long in the kitchen (above) with three additional radiators in the living room, including one long low Grace tucked below the window seat.

Don’t think sizing up your radiators also has to mean digging deeper into your budget - our radiators are priced so that the section cost falls the more you need.

Low radiator under window seat in open plan living room with log burner
Grace 4 Column 360mm under-window seat.
 Grace 4C 960mm at 24 sections long
The log burner creates a cosy feel in this open-plan sitting room which links with the kitchen and dining space.

The main house features an open-plan living space which combines a sitting room, kitchen and dining area.
By heating a single, central ‘hub’ within the home, the bedrooms above benefit from the residual heat from downstairs so overall less heat is required upstairs.

old fashioned radiator in open plan shaker kitchen
A central dining table with pendant lights makes for a convivial, multi-use room.

The bespoke kitchen units installed by the previous owners were salvaged and repurposed to create a simple, pared back cooking and dining area.

Log burner in inglenook fireplace of refurbished farmhouse with Camerich sofa
The snug was once the farmhouse kitchen and still has the original inglenook hearth.

The occasional snug room can also be kept cooler, heated only when in use either by central heating or log burner. Energy-saving TRVs turn the radiator off when the log burner gets up to temperature.

As well as the simple principle that heat rises, the orientation of the house should be taken into account. Working with the natural circadian heating cycle when positioning radiators will reduce wastage.

The main house at Lower Glasnant faces south

The main house at Lower Glasnant faces south. Two large bay windows and a set of french doors make the most of the heat and light from the sun as it moves around the building. The north-facing back wall of the house abuts a steep bank and sees very little sun so the majority of the ground floor radiators are placed on this side of the house to create a balanced heating load.

Lower Glasnant is available to hire on Airbnb.


Beds and sofas by Camerich

Selected furniture from The Old Electric Shop, Hay-on-Wye

Selected lighting BTC