(Photo: The Straits Times) Pops of green lighten the grey, rough plaster facade of the house.

Architect Warren Liu's house may be sandwiched between two single storey terrace houses in Opera Estate, but it hardly feels claustrophobic inside.

Wind flows easily through the house, thanks to large openings in the facade at the front and back of the house.

Instead of windows on the second level, Mr Liu, who is the principal of architecture firm A D Lab, opted for mechanised shutters.

These come down when the family turns in for the night or when it rains heavily. Otherwise, they are up most of the day and help enhance the home's openness.

These shutters are also used on the third level, where there is a recreational area.

The house is so open that birds have flown through it. Mr Liu, 48, who lives there with his architecturally-trained wife and their two children aged 10 and 12, says: "Big windows would have cost a fortune and shutters are a practical, cheaper option. We get so much sunlight here that there's no need to rely on artificial light as much."

(Photo: The Straits Times) Architect Warren Liu in his living room, which is connected to an outdoor garden.

There is an airwell in the centre of the house that acts as a wind conduit and channels cool air down.

Although the house sits on a site area of about 1,400 sqf, it feels bigger than it actually is indoors, thanks to tiered levels linked by short flights of stairs.

For example, a couple of steps down the living room takes you to the open-concept kitchen and dining room.

The children's rooms and the recreation room are on the third level, while the master bedroom and guest bedroom are on the top floor.

The guest room has a steep staircase which leads you to a cosy outdoor nook parked in between the two pitched roofs of the house. Here, faux grass covers the floor.

The green-fingered architect has filled his home with plants, such as a leafy ficus tree in the centre of a water feature at the bottom of the airwell.

(Photo: The Straits Times) The dining room shares space with an open-concept kitchen and a pool.

He built a seating area on one side of the water feature, where one can work or read. It also provides extra seating too if they run out of space at their dining table.

The front garden, which is above the car porch, is a quiet, hang-out spot with a view of the street below. Leafy green plants shield the family from passers-by.

The stairs between the recreation area and children's rooms have money plants in hydroponic pots creeping up tension cables, which replace the traditional balustrade. There are also indoor trees planted in big pots.

Mr Liu says: "You get that benefit of being close to nature even if you're indoors. The plants also help to cool down the house."

(Photo: The Straits Times) The master bedroom opens up to a balcony (above). A roof pitched with faux grass muffles the sound of rain.

With space being in short supply, many of their furniture pieces do double duty: A couch in the recreation room can be turned into a pull-out bed, while a treadmill has a built-in desk and can be converted into a bench when needed.

Mr Liu also got creative with the bathroom in the master bedroom. It is housed in a glass box but outsiders cannot look in as one-way mirror glass was used.

He did this so that he would not have to put up brick walls, which would occupy more space than glass.

The entire house cost about $800,000 to build from scratch.

Mr Liu was able to use the space so creatively that he even managed to fit in a 2.2m-wide pool next to the dining room.

He says: "Even on a small plot of land, we managed to do quite a lot, and still keep the space open and bright."

(Written by Natasha Ann Zachariah for The Straits Times)