Sun on the dark side

Facing south with magnificent valley and mountain views, they faced the challenge of designing a solar passive home that would keep them warm during winter, two months of which would be without any sun on the house.

There are many properties in Nelson city which lose the sun during the winter months and suffer for it because of bad design and orientation, lack of insulation and unsustainable heating. These properties are typically damp, with mould and condensation on the inside of windows, affecting the health of the occupants. Colds and flu, allergies and asthma are just a few of the symptoms of living in such homes.

So it was amazing to walk into Kirti and Sky's home, light and airy, warm and dry, where the astute selection of materials and products, and clever orientation maximising solar gain and passive solar heat retention have created an amazing space to live in – proof that south-facing sections can sustain habitations if well designed and built sustainably.

The 210sqm house lies east west, sitting on a flat pad up a zigzag driveway. The contemporary exterior of painted fibro-cement with batons sits comfortably with the light filled interior and extensive use of natural materials, all chosen for their environmental friendliness and energy efficiency.

The living-dining space is open plan but with the kitchen tucked around the side of the dining space, offering a sense of separation. At the east end is Kirti's office-workout room, a bedroom and bathroom for guests. The other wing of the house to the west features the master bedroom, ablutions and Sky's music room, which has access outside to a large courtyard relaxation space.

Sky and Kirti both worked on a simple design which would fit in with the landscape and follow the natural lay of the land, in "form follows function" philosophy. They worked with architect Mike Davies, then Mark Fielding from Ecotect to complete the plans, and enlisted Gerald Gaskell and Peter Randall to build.

Kirti worked with the builders daily, while Sky was kept busy with the daily cleanup of materials on site. Since the build, they have had volunteer workers from the Woofer scheme helping, in return for food and accommodation. Kirti says it has been satisfying to have them on board as he sees important principles of sustainable design are being passed onto others during their stay.

The choice of materials and products was important to Kirti and Sky to support the clever solar passive design. They chose to use a relatively new product in this country, German designed UPVC windows with steel interior framing. Essentially a plastic medium, UPVC is low in conductivity, lower than standard aluminium, meaning heat is retained inside in the crucial winter months, and kept outside during the summer. They have a concrete pad with 200mm polystyrene sheeting for extra insulation, both under floor and around the house perimeter. On the high feature walls in the main living dining space is a mud brick veneer, which acts as another heat sink. Winter heating is from a Metro Rad 23- kilowatt wood burner with wetback which feeds hot water to six flat radiators around the house. There is also solar hot water, which keeps their power bill to a minimum.