Turning up the heat on net zero
Peter Ranscombe explores why heat pumps are only part of the story when it comes to warming rural homes, and that insulation remains key as cold winds whip around Scotland
Two recent conversations left me feeling worried. The first was with a lawyer who wanted to install an air source heat pump in their home but couldn’t make the costs and benefits stack up; the second was with an entrepreneur who switched back to oil to heat their holiday cottages because it was cheaper than electricity.
Those two cautionary tales left me deflated. Burning coal, gas or oil to heat our homes releases carbon dioxide, methane and other greenhouse gases, adding to global warming.
The alternative is to heat buildings through clean sources of power. Burning hydrogen instead of natural gas is one option, but the jury is still out on the role it will play – ‘green’ hydrogen is made by using electricity generated from renewable energy like wind and solar power to split water into hydrogen and oxygen, and so opponents argue it’s more efficient to use the electricity itself for heating.
Forget about storage heaters though – those horrible relics of a bygone era that were the scourge of student flats and which, sadly, are still far too common in many rural parts of Scotland. Virtually impossible to control, storage heaters drew in off-peak power to heat bricks, which then radiated that warmth back out again, often at unpredictable times of the day and night.
Instead, the great hope for cutting emissions from heating is the ‘heat pump’. They come in a variety of flavours – air source heat pumps, ground source heat pumps, water source heat pumps – but, in essence, they all operate in the same way.
Heat pumps capture heat from outside and move it into buildings. They don’t burn fuel themselves, so they don’t emit carbon dioxide or other greenhouse gases, but they are powered by a relatively small amount of electricity, and so that needs to come from clean sources, either from the national grid or, in remote areas, from on-site wind turbines, solar panels, or other renewable energy devices.
In an air source heat pump, cold air from outside is used to cool a liquid inside the heat pump, which is then compressed, a process that raises its pressure and also its temperature. That higher temperature can then be used to heat a building.
Ground source heat pumps involve burying liquid-filled tubes underground to extract heat, while water source heat pumps place those tubes into lochs or ponds. If you want to take a deeper dive into the inner workings of a heat pump then there are some nice diagrams and explanations on the Energy Saving Trust’s (EST’S) website.
Sadly, there’s a catch though. Heat pumps run at lower temperatures than the current gas-fired or oil-fired central heating boilers to which we’ve become accustomed.
That means installing the heat pump itself is only part of the story, with many people also needing to replace their radiators with larger models or fit
more radiators inside their homes to get the same level of warmth. Depending on the age and diameter of their central heating pipes, those might have to be replaced too.
The headline cost for installing an air source heat pump sits at about £11,000, with the Scottish Government offering £5,000 grants. Fitting radiators and pipes would push up that cost.
After last October’s rise in the energy price cap, the EST estimates that the potential annual savings when installing an air source heat pump in an average-sized, threebedroom detached home would be £1,500 compared to old storage heaters, £590 compared to an old liquified petroleum gas boiler, or £395 against an old gas boiler.
But two figures on the chart on EST’S website raised this tightfisted teuchter’s eyebrows: an air source heat pump would cost £330 more to run each year than a new A-rated oil boiler and £80 more than a new A-rated gas boiler, if you’re lucky enough to live somewhere with mains gas.
It’s important to remember though that those illustrations are for today’s fuel prices. Over the years and decades to come, Scotland will generate more and more electricity and extract less and less oil and gas in order to hit its legally-binding 2045 net zero carbon emissions target – which is only 22 years away.
Heat pumps also mean people need to change their habits. They take longer to heat a home from scratch, and so need to be set appropriately to maintain a constant heat, rather than the instant gratification of turning on an oil-burning central heating boiler using a mobile phone app.
‘That’s why, when you’re retrofitting an old property, we suggest having an alternative heat source as well,’ explains Ryan Timpson, a chartered surveyor in Savills’ Perth office. ‘If you’re going for retrofitting an air source heat pump system then maybe go for a wood-burning stove as well, so you have that top-up on a cold day.’
Insulation is also key. With heat pumps working at lower temperatures, homes need to be insulated to retain their heat; it may sound boring, but – as a nation – we need to tackle dull issues like loft insulation, cavity wall insulation, and even internal wall insulation in some homes. Caroline Webster, an associate director in Savills’ Inverness branch, highlights the need to assess each home individually to make sure the right system is selected. ‘If you’re retrofitting then it’s not a case of “What system do I want?” it’s “What’s the performance of my house with that system?”,’ she says.
‘For an air source heat pump, you’re going to have to retrofit a whole load of insulation. It’s a different system completely from a wet system that comes from an oil-fired boiler.’
Country estates face a further complication. Under proposed rules, privately rented homes in Scotland will need an energy performance certificate (EPC) rating of C by 2025 for new tenants, and 2028 for all tenants.
EPCS are based on the price of the fuel used to heat the property, and so landlords that need to raise their EPC rating are faced with a dilemma if they also want to cut their carbon emissions. ‘Electricity doesn’t always work for EPCS, unfortunately – oil is still the best way to go for EPCS,’ says Webster.
While the relative costs of electricity and oil will play themselves out over the years and decades to come, it’s within government ministers’ gift to reform EPCS. Until a healthy dose of common sense prevails, many rural landlords will be left out in the cold when it comes to heating their tenants’ homes.
“
Heat pumps capture heat from outside and move it into buildings