Social housing project celebrates form and function

Vision West Community Trust teamed up with Unitec students to develop the three prefabricated pavilions in Henderson. Photo / Jackie Meiring

A social housing project in West Auckland points to a positive future when it comes to marrying good design with low-cost construction.

We are a fairly conservative population when it comes to housing.

Most of the new houses going up on infill sites and new subdivisions are another, albeit slightly updated and larger, version of what our parents and grandparents built.

But when we look at building affordably and sustainably, different design models need to be considered that adapt - not to a preconceived idea of style - but to the site, climate and the most appropriate building technologies available.

There are many excellent precedents in the city and country: elegant buildings both large and small that use locally sourced and sustainable materials, and are designed to maximise the sun's energy and minimise heat loss.

The West Auckland project shows how small, low cost buildings don't have to be characterless in their design. Photo / Jackie Meiring

In terms of affordability, there is still much to learn from industrial buildings: speed of construction, minimal waste and prefabricated modular elements. Architects have explored 'non-traditional' architectural styles since the 1920s, and while regularly built by the rich (pick up any glossy magazine for proof) they have been used far less as potential models for medium and low-cost housing.

This project in West Auckland provides a wonderful case study for how small, low-cost buildings can utilise innovative design and construction to create sunny and characterful high-performance homes.

The client, VisionWest Community Trust, teamed up with Unitec's student programme Studio 19, led by Dave Strachan of Strachan Group Architects, to develop this series of three prefabricated pavilions for a site in Henderson.

Two of the pavilions are linked by a glazed entry hall to form a 104-square-metre, four-bedroom main dwelling (living rooms are in one and bedrooms in the other).

An additional single pavilion provides a 58-square-metre, two bedroom minor dwelling for the same site. The buildings step down the hill making the most of the gentle contour to create privacy and share views. Native planting is placed to create screened outdoor space and tie the whole site and design together.

The design aesthetic is based on the idea of an 'urban bach', where open-plan living areas flow onto sheltered decks, opening to garden and view, and the architecture can be humble.

Metal cladding and plywood interior lining have a rich legacy in this country and have been used here not just for aesthetic reasons, but also for structural integrity during transport, cost and ease of maintenance.

Despite the relatively small floor area of the main house, by today's standards the open-plan living, kitchen and dining space (measuring 4.8 by 8.6 metres) feels generous, and creates a successful social family hub so critical in the brief. In order to prioritise this space, economies were found elsewhere: the laundry is in a cupboard; corridors are multipurpose (there is only one true corridor which contains a study); bedrooms are kept as small as practical; and furniture is built-in and wall-hung, thus increasing the sense of space.

This project in West Auckland provides a wonderful case study for how small, low-cost buildings can utilise innovative design and construction to create sunny and characterful high-performance homes

Its 'green' credentials are extensive, and cover everything from low construction waste to sustainable, local materials to passive solar design to low energy appliances to low-flow water fittings to low-toxicity finishes.

At its heart - and what affects the design of the form and envelope the most - is the passive solar design principals, or what Strachan prefers to broaden to "climate responsive architecture".

Thermal mass, the right amount and orientation of glass, overhangs, high insulation values, adjustable ventilation panels and small or no south-facing windows, can mean artificial heating is not required for those spaces in winter.

The design aesthetic is based on the idea of an 'urban batch', where open plan living areas flow onto a sheltered outdoor area. Photo / Jackie Meiring

To achieve this in a prefabricated building meant using a transportable thermal mass, in this case a 30mm concrete composite topping to the fl oor panels. And another key innovation for structure and cost are the prefabricated 'structurally insulated panels' for the walls and roof.

These are essentially sandwich panels with a pre-finished interior lining bonded to an insulation core, which is then finished with Colorsteel metal for the roof and south-west walls, and 12mm Shadowclad over cavity for most of the external cladding.

They provide an insulation value 50% above code requirements. Strachan believes this project has the potential to change the way New Zealand approaches social housing.

"Prefabrication in factory-controlled conditions is becoming increasingly important as an alternative to site building, particularly in New Zealand's wet winters," he explains.

"It offers the advantages of speed, quality and cost, and as such prefabrication should now be considered a 'preferred' method of construction over traditional site build techniques, and not just for social housing."