What is the brief for the most sustainable residential development? What is the most fully rounded solution to best address the triple bottom line of environmental, social, and financial considerations? The surprising answer can be found in nine criteria that are all running in one direction.

Dwelling size

Modesty becomes us now. We’ve pushed the boundaries to have the largest houses in the world, nudging 100 sqm per person. Grossly unsustainable in energy, materials and space, we should be drastically downsizing to dwellings with about 20-25 sqm per person (which is a single person room in a boarding house). Let's say a one-bedroom dwelling is 40 sqm, a two-bedroom is 60 (current granny flats), and a 3 bed dwelling tops out at about 75 sqm. The smaller apartment costs less to build, operate and maintain. It ticks the financial affordability box.

Curiously these sizes are far less than those dictated in the NSW Apartment Design Guide, the ADG, which suggests 50, 75 and 90 square metres respectively. The document, written to encourage quality apartment designs, mistakenly assumed we needed to replicate house sizes. Any study of apartments in Berlin, Barcelona or Buenos Aires would show how fallacious that idea is.

Density

Outside the dwelling itself, the most important criteria for sustainability, is density. The proximity to services, education, health, shopping and so on, determines the energy needed for travel and infrastructure, which accounts for a quarter of all energy demands, and currently the most fossil fuel reliant. Closeness rules the environmental indicator.

Recent research talks about the ‘Goldilocks density’ but shows how it varies all over the world. Experts differ, but my studies suggest that a density of 50-60 dwellings per hectare (dw/ha) is the sweet spot in Australian cities. Not too cold at 10 dw/ha for detached freestanding homes (hugely car dependent) and not too hot at over a hundred dw/ha (demands for lifts and mechanical ventilation drive up energy costs). That rules out both those extreme typologies

Community

A group of dwellings should form a small community within the larger. Again we need to find the ‘just right’. Not isolated like detached houses or terraces, but not so many to drive strata anxieties with fifty, or a hundred or more dwellings. This is the key social indicator. Eight to sixteen dwellings is a happy medium, to know your neighbours, look in and care for them, share resources, but not so many as to feel overwhelmed by innumerable people you never know.

The first three criteria, critical to the triple bottom line, suggest a typology with about a dozen small dwellings, grouped together at, say, 50 dw/ha. Thus the site we need is about 1,500-2,000 sqm; the area of about two to three conventional detached houses.

Open space

In the temperate climate of the big ten (cities) we comfortably live outdoors and have developed a love of what was once Burke’s Backyard, now Costa’s gardens. We prefer real soil at ground level rather than inhospitable rooftops or tiny balconies. Let's suggest that about half the site area (700-900 sqm) is available for landscape, growing trees and vegetables in deep soil, drying clothes and outdoor activities.

Again, Australian apartment regulations were framed to replicate the ubiquitous detached home, rather than understand the quite different needs of apartment dwellers. So the outdoor is reduced to an ineffective balcony, unusable in most weathers, and only used sporadically or for a bit of storage. Meanwhile the residents, without their own ground gardens, discover the joys of the open space in local parks and communal gardens, known for centuries in Europe and Scandanavia.

When space is a premium, flexibility is the key. A balcony in a temperate climate is better used as a closed-in fully-glazed sunroom in winter, and then opened up as a veranda in summer. Making balconies mandatory only serves to drastically drive up costs for an under-used space, but opens a whole ocean of waterproofing (and building commissioner) issues.

Height

Many studies show the optimal maximum height for dwellings is where an occupant can clearly distinguish the features of a person in the street below, call to them, and provide passive surveillance and a connection to the surrounding community and landscape. It suggests four storeys, five at the most. Any higher, it divorces residents from the surroundings, and alienates them from the active world and community.

Whilst Oscar Newman is most closely associated with these ideas, you might also like to read about Alice Coleman, a geographer who championed the idea of defensible space in her critiques of the failed English public housing schemes, that we sadly slavishly followed.

Vehicles

Cars destroy good medium / high-density design. Space hungry, the circulation and parking sometimes take as much space as the apartment it serves. We can reduce the car impact three ways. First, build close to public transport for regular daily needs. Second, adopt car share on, or nearby, the property, perhaps even run by the small community of 12 units. Then we halve or quarter the number of cars that are needed.

Needed cars should be parked in carports, the open air or small garages without the need for mechanical ventilation. Basements are ruinous. They are expensive, material hungry, single use, inflexible spaces, that interfere with the hydrology of the water table, and demand mechanical ventilation. To be avoided.

So, our brief now demands parking for three or four cars at ground level, tucked under the building and not reducing the garden area or in a basement. And the plentiful pushies are locked in the dwellings or under the stairs, not outside where they disappear.

Materials

The building’s materials should meet the 3 ‘L’s’ of long life, loose fit and low impact. Ideally, the envelope would follow the key rules of high insulation and thermal mass. Heavyweight materials, masonry and concrete, are preferred to lightweight frame with plasterboard and autoclaved aerated concrete (AAC). Critically the mass also provides good acoustic isolation, so needed in apartment schemes.

The building needs to be durable, for longevity with low maintenance. Again, solid walls of brick or concrete masonry, with concrete floors meet the need. Pitched roofs, that accommodate photovoltaics, shed water to storage tanks most efficiently, and avoid the costs and ongoing problems of complicated trafficable and green roofs, pushing up apartment prices. Affordability to the fore with conventional materials.

Energy

All dwellings must be designed for minimal energy use (heating, cooling, hot water, and lights). In addition to the insulation and thermal mass outlined above, natural light and ventilation are critical. The energy demanded in communal areas must be minimised, encouraging the use of stairs. Without a basement there is less demand for mechanical ventilation and lifts. Open stairwells and internal passageways with light and ventilation should be the norm.

Accessibility

Accessible apartments at ground level can be directly connected to car parking. The idea of ‘adaptable’ apartments in the NSW ADG is a farce, an expensive one at that. Despite enquiries, I know of no apartments that have ever been adapted to accessible; there is no register, and no way for a disabled person to know what is available. The sooner the dumb bits of the ADG are dispensed with, and liveability code for every apartment is introduced, the better.

The brief, in summary

We are looking for about 12 apartments on 1500- 2000 sqm of land, in a single ‘community-style’ building, with half the site available for planting gardens and trees. No basement allows for good root structure to trees in deep soil. The building is located on or near a main transport route, has few cars to share amongst the owners or for residents with particular needs. The building is an integral part of a 15-minute city where all needed services (work, education, health, shopping) are within walking distance, or a maximum 15 minutes’ drive.

The building is about four storeys tall; three or four dwellings per floor; a central liftwell and modest foyer spaces; naturally lit and ventilated. The dwellings are made from well insulated heavy mass construction with good thermal and acoustic properties, also naturally lit and cross ventilated with at least two walls at right angles. The dwellings have no balconies, but sunrooms for the temperate climate, closed in winter and open in summer.

Any idea?

Sounds wonderful, but does such a typology exist? OMG, it does. It's the red, orange or yellow brick, three to four storey walk-up blocks of flats, so reviled by planners and architects. The most sustainable residential buildings in our cities are the ugliest and most hated.

I’ll let you digest that for a week, before returning to praise the unlovable even further, and to look at how the original model may be improved to meet today's standards. Meanwhile here’s some of my favourites (on the road to Bondi).

Reference: ToT 163: week 22/ 2023, Searching for the most sustainable residential typology.

Tone Wheeler is an architect / the views expressed are his.

Long columns are Tone on Tuesday, short shots every Friday in A&D Another Thing.

You can contact TW at toneontuesday@gmail.com

Tone Wheeler

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