When David Hills and Deborah Saunt began plans to build a home in the backyard of a 19th-century house in London they had a height limit, so they decided to bury half the house underground. They also used mirrors as cladding to help hide the home, reflecting the surrounding vegetation instead.

Their home in Clapham Old Town is in a conservation area surrounded by 23 neighbors who once overlooked the overgrown garden of sycamores and ivy. In order to replicate that lush environment, they planted a green roof, and Hills and Saunt designed a green roof with drought-tolerant sedum plants, which require only a very thin buildup and promote wildlife. They also planted new trees, like mulberry, around the home.

To create a secure and simple structure for an underground home, they started with a concrete box:

“We dug a big hole to build the house in. It’s just a square box. That’s also cheaper. Every time you have to push in and out, then you’re building really complicated shuttering. So when you go down, the simpler you can make it, the better.”

Wanting as much daylight as possible, they dug sunken courtyards around the home to act as lightwells for the downstairs. Upstairs they used skylights and strategically-placed windows (to protect the neighbors’ privacy and theirs) to keep artificial light to a minimum.

With half the home underground, the earth helps maintain a stable temperature, but there’s a heat recovery system when heating is necessary. Rooftop solar thermal panels heat the home’s water.