They engaged Wendy Perring and Collette Raine of PAD Studio because of their knowledge of the local area and its planning laws, and their experience in designing energy-efficient buildings.

“We always work from a fabric-first approach, making the envelope of the building as energy-efficient as we can,” says Perring. “It’s about clever design: maximising the solar gain in winter and minimising it in summer, and making the envelope of the house work really hard for you.”

In the case of this house, they chose materials specifically to meet those requirements, with a brick exterior and plenty of exposed brickwork on the inside, too. “A lightweight building, such as one with a timber frame, will heat up and cool down very quickly,” says Perring, “whereas a house with thermal mass, made from concrete or brick, will absorb the sun’s energy during the day and, when the temperature drops at night, release the energy back out. There’s much less fluctuation in temperature, so you’ve got a very comfortable internal environment and you don’t need to boost the heating in the evening, which is really energy intensive.”

To help keep the house cool in the summer, they designed an overhang that runs around the building’s exterior. “A lot of people say it looks quite Frank Lloyd Wright,” says Perring, referring to the American architect whose Prairie Style buildings featured flat roofs and overhanging eaves, “but what it’s actually doing is shading the windows in the summer, when the sun is higher in the sky, while allowing it in to warm the house in winter, when the angle of the sun is a lot lower in the sky.”

Passive ventilation via high-level windows, which the Thompsons usually have open, also helps to cool the house in the warmer months: “In the summer, with the doors open onto the terrace and the high windows open at the back, you get this lovely cool breeze coming through the house, which works really well,” says Perring. “Nobody should be using air conditioning.”

The couple are now paying about 80 per cent less on energy bills than they were in their former home, which Charlotte attributes in large part to the efficient insulation installed in the house, and the fact that the windows are ­triple-glazed. This was a significant investment (triple-glazing can cost up to 20 per cent more than double-­glazing), but, says Raine, “it really does make a difference”.

Charlotte agrees: “During our first winter here, it snowed at one point and I said to Graham that I thought it felt a little bit on the chilly side in the house. It turned out our thermostat was on the frost setting. The fact that it was only slightly cooler inside than we wanted it to be, even on the frost setting, was incredible.”

The space and water heating are via a ground-source heat pump, which uses a heat exchanger to take energy from the ground. “You still need to put electricity into it, but it’s really efficient,” says Perring, “so with every unit of electricity you put into it, you get about four out of it.”

Solar panels on the roof generate electricity (the Thompsons are now looking into buying a battery so that any excess solar power can be stored). And as all the energy-efficiency measures were factored into the design of the house right from the start, rather than bolted on at the end, the building is designed in a way that the panels on the roof cannot be seen from ground level.

The couple moved into their new house in July 2019. “It felt like home straightaway,” says Charlotte. “The whole process has been a really pleasurable experience. We feel astonishingly privileged to have been able to build a house like this, with elements such as the heat pump and insulation that will look after us for a long time.

“Downsizing can be perceived as a little sad – something that you do when you are leaning towards the end of your life – but this has really been an adventure.”

How to save energy and money in the kitchen

Energy ratings are everything

Given that the fridge is on all the time, it’s no wonder that it accounts for 63 per cent of the total electricity used in our homes – or more if you have a geriatric American-style fridge-freezer. According to BeEco, switching a fridge to a new model that is better by two energy-rating grades can save £190 on energy bills. The new rating system for cold appliances can be confusing: it now runs from A to G (previously A+++ to G), with icons to indicate chilled and ice compartments and noise emissions. Today’s most efficient appliances are awarded a B or C (and what used to be A+++ is now D) to encourage manufacturers to make even more efficient appliances. Ali Hamid, of Jigzaw Interiors in London, recommends LG for fridge-freezers (one of its models is already A-rated, using 60 per cent less energy than a standard unit), as well as Bosch and Siemens. “If you need more storage space, two freestanding fridge-freezers can be more energy efficient than one enormous American fridge-freezer,” he says.

Dishwashers are another energy-saving game: a dishwasher uses seven times less water than handwashing, but you can save even more water and electricity by choosing an ultra-efficient machine with a half-load setting. “The best models sense what they have inside and use the required amount of water,” Hamid explains.

For those without the budget for one of Miele’s G7460 SCVi dishwashers (£1,749; miele.co.uk), which warms up water using previously stored heat, he recommends the Siemens IQ700 range of dishwashers, from £999.

1970s flooring

While reclaimed wood flooring seems the obvious choice for a carbon-neutral kitchen, installing it can be so time-consuming and costly that many people decide against it. Cork flooring is currently the most popular alternative, says Tim Burgess, of Zero Kitchens. It’s soft and warm underfoot and hard-wearing, and companies such as colourflooring.co.uk are pushing boundaries. Linoleum is also making a comeback, along with terrazzo tiles, from bertandmay.com, which were once used on supermarket floors and are made of recycled scraps of glass, marble and quartz.