Solid fuel heating systems & boilers

If you live in an area where a mains gas supply isn’t an option, a solid fuel heating system could be an alternative way to heat your home and water.

But how do solid fuel heating systems and boilers work, and are they a sustainable way to heat your home?

If you live in an area where a mains gas supply isn’t an option, a solid fuel heating system could be an alternative way to heat your home and water.

But how do solid fuel heating systems and boilers work, and are they a sustainable way to heat your home?

Sofia Hutson
From the Energy team
7
minute read
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Posted 6 JULY 2021

What is solid fuel heating? 

Solid fuel heating systems work by burning solid fuels like wood, peat or coal to heat your home and provide you with hot water. They can be used as an alternative to gas, oil and electricity, especially in off-grid rural areas that don’t have a mains gas connection. 

There are two main ways to use solid fuel for your hot water and heating supply: 

  • Wood burning stoves
  • Biomass boilers

Solid fuel stoves 

The most common type of solid fuel stove is a wood-burning stove. They typically have a glass-fronted panel and can run on wood logs, pellets or briquettes. There are also multi-fuel stoves, which can burn both wood and smokeless coal. 

Considered less messy than an open fire, wood-burning stoves are incredibly popular in the UK, instantly adding a warm and cosy feel to a room. Wood burners are usually used to heat just one room, but they can spread the heat to other areas via a connected flue or chimney. 

Wood-burning stoves can also be plumbed into the central heating system and used to heat radiators and provide hot water. If you don’t have mains gas, a wood burner can be used as your main domestic heating system. If you already have a gas or electricity system, the wood burner can be linked to your conventional heating system. You could use gas or electricity to heat your home until the solid fuel stove has had a chance to warm up, then switch it off until the fire dies down.

Wood burners could also be used to heat up your water via a hot water cylinder. Connecting a wood burner to your central heating and/or hot water system can be complex and expensive, though. In most cases, you’ll also need to install a vent to prevent pressure from building up in the system – for this reason, they’re not compatible with combi-boilers. A wood burner should only ever be linked to your central heating or hot-water system by a qualified heating engineer

Solid fuel stoves – advantages 

  • Create a warm, toasty and inviting atmosphere – there’s nothing more homely than a real fire on a cold night
  • Can provide an effective alternative heating system for rural homes that don’t have a mains gas supply
  • A comforting and reliable heating source during a power cut
  • Wood is pretty much carbon neutral and can be considered ‘renewable’ fuel if it comes from a responsibly sourced working forest (meaning when a tree is cut down, another one is planted in its place)
  • Low running costs if you have your own woodland and an abundant supply of seasoned wood
  • Recycled wood briquettes are cleaner, heat more efficiently and are easier to store than traditional logs 

Solid fuel stoves – disadvantages 

  • Higher-quality wood heats more effectively, but is also more expensive to buy – especially kiln-dried logs
  • You’ll need a constant supply of wood and enough space to store it
  • If you have your own wood supply, you must make sure logs are seasoned and dried to remove as much moisture as possible before using them – some logs can take between one to three years to season from fresh
  • Ash needs to be cleaned out regularly and your chimney swept at least twice a year
  • Will only heat a single room unless it’s connected to the central-heating system

Biomass boilers 

Modern biomass boilers can provide an incredibly efficient way of heating your home and water, while cutting down on CO2 emissions. Thanks to modern technology, the best biomass boilers can operate at 90% efficiency, much higher than conventional boilers and electric heating systems. 

Biomass energy is considered a source of renewable energy, as it comes from natural, organic materials like wood, charcoal and even animal dung. 

Domestic biomass boilers use wood logs, pellets or wood chips to deliver heating and hot water to your home. As they only produce carbon that was originally absorbed by the trees, they’re considered a carbon-neutral heating source. 

Depending on whether you’ve got mains gas or not, a biomass boiler can provide all your heating and hot water needs, or it can be linked and used together with a conventional gas boiler or electric heating system.

There are two types of biomass boiler models: 

  • Automatic – pellets are automatically fed into the boiler by a ‘hopper’, and the heat can be controlled automatically. These provide an easy-to-use, no-fuss solution, but they’re more expensive to buy and install.
  • Manual – you have to manually feed the wood into the boiler, but they can be cheaper than automatic models. 

Biomass boilers are typically larger than a regular combi-boiler, so you need to make sure you have the space to store both the boiler and the wood. The upfront costs to buy and install biomass boilers can also be pretty high compared to other new heating systems. The good news is that you might be eligible for payments under the government’s Renewable Heat Incentive

Biomass boilers – advantages 

  • Low carbon emissions
  • Fantastic energy-efficiency
  • Low maintenance – produces far less ash than log fires
  • Some automatic boilers allow you to store up to a year’s worth of pellets
  • Can provide heating and hot water for the entire property
  • You may be eligible for Renewable Heat Incentive payments 

Biomass boilers – disadvantages 

  • More expensive to buy and install compared to gas, oil or electric boilers
  • Bigger than a regular gas or electric boiler
  • You’ll need additional storage space for logs, pellets or chips
  • You might need planning permission
  • Unsuitable for flats and small properties in urban areas 

Top tip

Make sure you fit a carbon monoxide alarm in the same room as your solid-fuel burner. Carbon monoxide is an invisible, odourless and deadly gas that is produced by blocked chimneys or flues. It’s recommended that you have your boiler serviced at least once a year and your chimney swept at least twice a year by a qualified professional.

Frequently asked questions

What is the ‘wet wood’?

Wet wood is unseasoned or ‘green’ wood that contains a large percentage of moisture. When burned, it releases damaging pollutants and far more smoke than dry, seasoned wood. Wet wood also produces more tar and soot, which can damage flues and chimneys.

As part of the Clean Air Strategy, the Government has introduced new regulations to stop the sale of wet wood in an aim to cut air pollution. From May 2021, wood sold in volumes of less than two cubic metres must be ‘dry wood’ with a moisture content of 20% or less and must display the ‘Ready to Burn’ logo. If you have your own wood supplies or buy more than two cubic metres of wet wood, you must follow advice on how to season and dry the wood properly before burning it.

According to the Department for Environment, Food & Rural Affairs (DEFRA), burning dry wood will give you more heat, produce less soot and can reduce emissions by up to 50% compared to wet wood.

Under the new rules, the government also aims to phase out the sale of traditional house coal by 2023.

How do solid-fuel heating systems compare to gas central heating?

As well as being the most popular heating source, gas is also one of the cheapest ways to heat your home and water. A gas boiler will heat up your home quicker than a solid-fuel system, and the room temperature is easier to control. As mains gas is piped straight into your home, you don’t have to worry about storage space for wood or coal. With solid fuel you risk no heating at all if your wood supply is running short. 

But, as a fossil fuel, gas is not renewable, and it produces more CO2 emissions than biomass energy. 

While biomass boilers are the most expensive type of boiler to buy new, the savings in fuel consumption and reduced emissions may make them a better long-term investment.

Can I switch from solid fuel heating to gas?

If you want to trade in an old and inefficient wood stove with a back boiler, switching to a gas heating system should be fairly easy – as long as you have access to mains gas. 

If you still want the cosy feel of a real fire, you could use gas to heat the whole of your house, and keep a wood-burning stove to heat your kitchen or living room. 

If you’re off-grid, laying pipes to connect gas to your home could be difficult and expensive, if not impossible. If that’s the case, you may need to consider electrical, LPG or oil-fired central heating instead.

What other types of renewable heating systems are there?

If you’re looking for renewable alternatives to a biomass boiler, you might want to consider air source or ground source heat pumps or water-heating solar panels. These low-carbon alternatives to fossil and solid fuels produce energy from two of the most sustainable sources on the planet: air and sunshine. You’ll also be able to claim for them under the Domestic Renewable Heat Incentive.

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