Which Renewable Heating System Should I Choose?
Discover the advantages and disadvantages of four different types of eco-friendly heating
Here, three Houzz professionals explain the pros and cons of four different renewable heating systems.
Professional advice from: Neil Rollinson of GreenGenUK; Tony Duffin of CLPM; Nev Galvin of A Greener Alternative
“Air source heating seems to be the most popular form of renewable heating,” says Neil Rollinson, who puts this down to its competitive upfront costs and simple installation.
“These systems work by absorbing warmth from the outside air and converting it into heat,” Tony Duffin says. “Some air source heat pumps just provide heating solutions for homes, while others can include hot water as well. They work best via underfloor heating.
“Installation costs range from £10,000 to £20,000, depending on the system installed and the size of your property,” he says.
“An air source heat pump can often make use of an existing central heating solution,” Neil says. “They also output as much as four times more energy as they consume, so they create a cost-saving against virtually all other heating fuels.”
“They can be installed in most locations, as they’re not limited by orientation, nor do they need a lot of space,” Tony says. “They also require minimal disruption to install and no extra delivery or storage of fuel.”
Tony also highlights the fact that they can work all year round. “An air source heat pump can continue to work effectively to as cold as -7ºC,” he says. However, he does stress that at much lower temperatures, they’re less efficient than running an electric heater.
He also points out that you’ll need to ensure your home is ready. “They’re only suitable for well-insulated, airtight properties,” he says. “And you might need to install a compatible heating system, such as special low-temperature radiators or underfloor heating.
“You might also need to install an additional system to provide hot water for your needs,” he adds, “and some of the fluids used within heat pumps for heat transfer raise environmental concerns.”
Heat pumps and solar panels use fluids with antifreeze solutions inside, and it’s advisable to choose these wisely. To ensure you use a biodegradable, plant-based product that will also protect your system, it’s best to consult a reputable professional who’s experienced in installing these systems.
Finally, he states that many regular plumbers lack the expertise to service the systems properly, which could lead to high maintenance costs.
“Ground source heating is one of the most expensive forms of renewable heating, but one of the most beneficial,” Neil says. “The pump extracts heat stored in the ground and converts it into usable energy to heat homes and hot water.”
“The system involves digging a hole [either vertically or in the form of a trench] and laying pipework, which absorbs the heat from the ground before transporting it and releasing it into your home via radiators or underfloor heating,” Tony says.
“A ground source heat pump will use electricity to power its compressor and pump water through its circuits, but the heat transferred into the home comes from the ground, so it’s free and is more sustainable than using fossil fuels,” he explains.
A good heat pump system will provide more heat energy than the amount of power it requires to work. A well-designed model can provide three or four kilowatts of heat for the consumption of one kilowatt of electricity.
“Costs vary between £25,000 and £35,000, depending on the type and size of home to be heated,” Tony says.
“They’re also quiet and require minimal ongoing maintenance,” Tony adds. “Heat underground is at a fairly constant temperature throughout the year, so there’s always a constant supply.”
Tony recommends installing photovoltaic panels alongside both air and ground source pumps for electricity, but warns that the supply will be low in the winter.
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“A ground source pump is best added when carrying out new builds or major renovations, as the works can be very disruptive,” Tony says. “Trenches or boreholes will need to be dug, meaning there may be additional costs for relandscaping your garden.”
You might also need to install a compatible heating system inside the home, as you would with an air source heat pump, Tony adds, and perhaps also an additional hot-water system.
Although installation requires a lot of thought, Neil suggests those using ground source will often see their investment repaid within five or six years.
Although it won’t directly heat your home, a solar thermal system is an energy-efficient way to produce hot water.
“The way solar thermal panels work is quite easy to understand,” Tony says. “The panels absorb heat directly from the sun. A heat-transfer system inside the panels produces heated water, which is then stored in a hot-water cylinder.”
“Flat plates or evacuated tube collectors are usually roof-mounted, and the size and scope of installation depends on the demands of the building,” Neil adds.
“Price of installation will depend on the number of panels,” Nev says. “For two panels with 20 collector tubes supplied and installed, it would be around £5,000.”
“The upfront investment is quite high,” Tony says, “but it’s compatible with most existing boilers, as long as you have a system with a hot-water tank with two coils in it.”
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Tony also points out the system’s seasonality and that less hot water is produced during the winter months. “You may be better off installing solar photovoltaic panels for electricity and fitting a controller that diverts excess electricity to heat your immersion tank,” he advises.
“Despite that, solar thermal arrays will supply virtually all of a home’s hot water for more than half of the year,” Neil adds.
“The panels are quite big, so you’ll need a large roof area to produce enough hot water,” Tony says. However, he adds that the angle and orientation of the roof are less important than for photovoltaic panels.
“Solar thermal also requires a dedicated cylinder, so you may need to replace your existing hot-water cylinder,” he says. “The system is not compatible with combi boilers, as they don’t have a water storage tank.”
Biomass boilers are more comparable to traditional heating systems,” Neil says, “but chips, logs or pellets replace fossil fuels.”
“They’re similar to conventional boilers, in that they both produce hot water and heat your home,” Tony says. “Unlike other renewable heating systems, the pellets, chips or logs being burnt will need to be MCS [Microgeneration Certification Scheme]-approved. This can make biomass trickier and more labour-intensive than other fuels.”
“Prices will vary depending on the size of system, type of fuel, levels of automation and fuel storage,” Nev says. “It can cost from £5,000 to install a biomass system, right up to £50,000 or more.”
Biomass is a sustainable choice, as long as you’re careful about where the fuel is sourced. “The most sustainable systems burn wood from trees that are grown, coppiced and then dried specially on the premises,” Tony says. “When grown in a sustainable way, it’s a genuinely renewable fuel – it will never run out. The fundamental source of energy that trees use to grow is the sun.”
Another point in its favour is that biomass can be stored. “So unlike wind and sun, it can be used on demand,” Tony says.
However, Nev points out that the emissions are offset. “The carbon dioxide released when burning biomass is equal to the CO2 that’s being absorbed in the original growth of the biomass during photosynthesis,” he says.
“When we compare with fossil fuels, taking all impacts into account, biomass emits 40% to 50% of CO2e [carbon dioxide equivalent, which measures carbon footprints] compared to using natural gas, 33% to 45% compared to UK electricity, and only 25% to 30% compared to coal,” Tony says.
Another thing to consider is storage, say our experts. “Customers opting for biomass installation will need to consider the delivery and storage of fuel, in addition to how the fuel is loaded into the system,” Neil says.
Do you have a renewable heating system – or are you tempted by one? Share your thoughts and experiences in the Comments.