Paradoxically, they opted for a life in the underworld because they wanted more space and light. But their decision to live underground has proved to be a winner - and in doing so they have become the owners of the first below-earth suburban house in the county.
"We live in a luxury bungalow whose roof just happens to be at ground level and whose garden is above us," says Jonathan.
"Basically, we dug a hole and put a house in it. With the light coming in from above as well as horizontally, we have a brighter environment than if it was coming in only through side windows."
Undermill, in Bushey Heath, Hertfordshire, took four years to build and cost about pounds 100,000 - and that figure includes "problems with the builders".
After a period living in the bright warm light of Australia, they dreaded returning to a "typically murky British home". Once they had decided to pursue the do-it-yourself option, the move towards underground living followed naturally.
"It's ideal for families with young children as it's so quiet," said Sue. "The neighbours don't hear us and we don't hear them."
The roof is made up of a one-metre-thick layer of turf on top of layers of thick polystyrene and concrete. This keeps the house well insulated and provides a stable indoor climate: in the winter it's warm and in the summer cool.
The house does have central heating, with the two central brick pillars acting as storage heaters, absorbing and retaining their heat.
Heating costs are far lower than in the other houses the Blacks have lived in, even though the square footage is twice as great. Energy conservation is a common design feature these days, but Undermill is more advanced and uses a computer. The central heating mechanism, controlled by microprocessor, finds out where the temperature is low and where it is high and heats up the required part of the house to keep an even temperature throughout.
A water storage tank on the roof collects rain and redirects it for flushing the toilet. Triple glazing retains the heat more efficiently in the winter.
The Blacks found that by building their own home they were not tied to an architect's "vision" and could incorporate whatever features they wanted. For instance, they have a single fixed vacuum cleaning collecting point outside the walls of the house, while each room has a hole in the wall where a vacuum hose can be attached.
The entrance is down a flight of stairs to the front door and then into a space which leads into the living and dining rooms, study, kitchen, three bedrooms and three bathrooms.
"There are really no disadvantages," says Jonathan. "There is no reason why underground homes cannot be built everywhere."Reuse content