How to Make a Heat Pump Work in an Old House

The Telegraph has published a fatuous article purporting to show how the owner of a 15th century listed cottage has made a heat pump work.

The premise of the article is that ignorance and incompetence on the part of installers, and flawed perceptions on the part of those rejecting the idea of heat pumps, are to blame for the belief that they don’t work in older houses.

Readers are introduced to 67 year-old Tim Adams, a software expert, whose house is classified as Grade II. He’s pictured proudly standing next to his heat pump, an installation big enough to pass muster with an American air conditioning system outside a motel in the Arizona desert. Not only does it partly cover one of his windows but also restricts access to part of a shed:

With its thatched roof and thick stone walls, rather than modern cavity wall insulation, it’s the sort of home you’d assume is wholly unsuitable for a heat pump.

While heat pumps can work in older properties, homeowners must often first pay for expensive retrofits, with larger radiators and added layers of insulation.

This is a huge problem for the Labour Government, which is desperate for homeowners to install the technology in Britain’s old homes. It faces little confidence that the technology works properly. In 2023, Vonjy Rajakoba, former Managing Director of Bosch UK, told the Telegraph heat pumps did not make sense in Britain’s “fleet of Victorian houses”. And it’s even harder to make them work in draughty and protected listed homes.

Despite these problems, it seems that Mr Adams has pulled off the seemingly impossible:

But Adams, 67, has persevered, and after two years of tinkering he has managed to get it to work decently well in his house in Wincanton, Somerset. “I was used to spending £1,000 a year on heating oil, but now my air-source heat pump costs me £720 for heating and hot water a year,” he says. “In a big old house that’s pretty good by anyone’s standards.”

The paragraph is loaded with points that need pursuing but aren’t. The heat pump apparently works “decently well”. What does that mean? Evidently not ‘very well’ or else it would say so.

“Two years of persevering”? What does that mean? Spending all day, every day fiddling about? We’ll see what it means in a moment.

A saving of £280 per annum (£5.38 a week)? £2,800 over a decade? £11,200 over 40 years? Indeed, since £280 is very close to the winter fuel payment taken off pensioners by the current Government in its not-mentioned-in-the-manifesto money-saving measure, why on earth don’t all pensioners simply install heat pumps in their ancient Victorian houses?

Given the costs of installing a heat pump (despite the grants), to say nothing of the concomitant costs of other necessary features such as upping central heating pipes to 22mm and installing larger radiators, all of which go unspecified apart from acknowledging these retrofits can be “very costly and onerous” in this classically useless piece of eco-journalism, it’s hard to see how any heat pump could ever pay for itself in an older building.

Exactly how much Mr Adams had to spend on getting his house heat-pump ready or precisely what he had to do are conveniently omitted from the article, leaving readers none the wiser about how this coup was pulled off, or the real costs, to say nothing of the disruption and inconvenience.

As far as your correspondent can see and at a bare minimum rough estimate, Mr Adams might possibly have recovered the costs by the time he is 107 years old, but very possibly he might have to hang on until he is 147 or older. By then his heat pump will long since have gone to join that vast rusting pile of decaying relics of early 21st century eco insanity. Indeed, it will probably have been expensively replaced several times by then.

Apparently, the solution to making a heat pump work is simple:

“It’s simply wrong to say they won’t work in old buildings,” says Adams. “You have to understand a less insulated house needs more heat pushed into it. Whether it’s an air-source heat pump or anything else. The key is to understand how much heat you need to push in and do that as efficiently as possible.”

In other words, you just apparently need more heat while at the same time as making the heat pump run at as low a temperature as possible. What could be easier? Actually, hanging on to your oil or gas boiler would be easier, but back to the secret of the magic heat pump:

“Understanding and using weather compensation has been vital to getting the best efficiency,” Adams says.

For the uninitiated, a heat pump weather compensation curve is the function that allows the system to adjust its flow temperature based on the temperature outside. The flow temperature is the temperature your boiler heats water to before sending it to radiators.

“Because you always want the heat pump to be running at the lowest possible temperature to get you to 21°C, you want the flow temperature in the radiators to be as low as possible,” explains Bean Beanland, of the Heat Pump Federation.

Quite how running a heat pump at as low a temperature as possible while at the same time compensating for fluctuating weather conditions especially in freezing conditions and thus keeping a leaky old house warm can all be achieved goes totally unexplained.

Incompetent installers seem to be the issue:

Adams spent the best part of two years fine-tuning his heat pump’s settings to work with his home, but he says many installers simply aren’t up to the task. “One of the vital things is the heat loss calculations for the property. Typically that’s done very badly by installers,” he says.

“They’ll do it by finger in the air. They’ll pluck a number from nowhere and it’s not a proper calculation. You can see why they’re not keen to necessarily spend a lot of time on it, but I think that’s something the MCS (the installers’ trade body) and the Government need to think about.”

So, now we know. That’s all you need to do. Find a heat pump installer with a degree in mathematics or a homeowner interested in spending two years tweaking the system and you’ll end up with a heat pump that works “decently well” in an old house.

Since even finding heat pump installers who are prepared to service these devices is hard enough, tracking down one with the qualifications, time and interest in trying to adjust something with the complexity of an 18th century chronometer might prove a little challenging.

But if you succeed you can enjoy the princely savings of £5.38 a week. You could spend the first tranche on a tin whistle and blow down it while Labour hopes for 600,000 heat pumps to be installed annually by 2028 and 1.6 million by 2035.