Demonising sprawl seems to be the mission of many planners, academics and journalists, but oftentimes zealotry leads to mistakes, as with this claim that infrastructure costs on the fringe are double those in established suburbs. I’m reminded again how easy it is to get the wrong end of the stick on this issue by a study released last week by the Architecture Faculty at Melbourne University.
The University’s media release tells us the study found “houses on Melbourne’s suburban fringe are responsible for drastically higher levels of greenhouse gas emissions compared to higher density housing or apartments in the inner city”. The Age ran with the media release, reporting that bigger dwellings and more car-based travel are the key reasons fringe houses consume more energy and emit more greenhouse gas than apartments.
I can’t refer you to a full copy of the study because the University didn’t make it available to the media or the public. That didn’t seem to worry The Age, but I think it’s an extraordinary decision – does the University exist to issue media releases or to undertake serious research? I contacted one of the authors who told me the study is a journal article and he couldn’t give it to me for copyright reasons. He gave me this link to the abstract. I’ve read the full article but if you don’t have on-line access you’ll have to spring for €35 if you want to read it.
A key part of the study is a comparison of the (embodied, operating and transport) energy consumption and greenhouse gas emissions of households in three building types – a 100 m2 two bedroom high-rise apartment in Docklands 2 km from the city centre; a 64 m2 two bedroom suburban apartment 4 km from the centre in Windsor; and a 238 m2 detached house in an outer suburban greenfield development 37 km from the centre (the latter is shown in the accompanying chart in two versions – a 2008 five star and a “future” seven star energy rated version).
I don’t know what the point of this sort of comparison is. Putting transport aside (you’ll see why later), there’s little policy value in comparing a $1 million plus Docklands apartment with a $500,000 plus suburban apartment in Windsor, much less comparing both with a $350,000 house and land package on the urban fringe (and I’d say Windsor is inner city!). Nor does a seven square two bedroom apartment seem like a practical substitute for the sort of household that buys a 26 square four bedroom house.
A better approach would’ve been to compare the greenfield house against a townhouse of similar value located in the established suburbs, say 20 km or more from the centre (or perhaps against a greenfield townhouse set within a walkable neighbourhood). Alternatively, the authors could have followed the ACF’s lead and compared the resource use of all suburban residents with those of inner city residents – but the catch here is the ACF found that, even though on average they live in smaller dwellings, inner city residents have a higher ecological footprint (see here and here)!
The study should be on firmer ground when it compares transport energy and emissions across the three locations, but it isn’t. The trouble is the study gets it completely wrong on this key variable and, frankly, the travel findings just don’t stand up. There are two key weaknesses.
The first is the authors’ decision to calculate the environmental costs of travel solely on the basis of the journey to work. This is a curious decision because work trips account for less than a third of all travel by Melburnians. Maybe that would be a ‘grin and bear it’ shortcut if work trips were representative of all travel, but they aren’t. Trips to work by car are much longer on average – and have lower occupancies – than those for non-work purposes. Further, public transport has high occupancies in peak commuting periods but when considered across all trips, emissions per capita for public transport are nearly as bad as cars. Because the authors assume 91% of the workers in the house drive to work compared to 50% in the suburban apartment and 25% in the Docklands apartment, restricting the travel calculations to work trips biases the findings against the house.
That questionable decision is reinforced by an even more puzzling one. For some unaccountable reason, the authors assume all jobs are located in the centre of Melbourne. They assume the workers living in the house therefore commute 37 km each way to work in the CBD. The reality is the median trip distance by car of outer suburban commuters is only around 20 km (and less than 10% work in the city centre). By significantly overstating the commuting distance the study further biases the calculations against the house. On the other hand, the authors underestimate the commuting distance of apartment residents, but the mistake is less significant for these two groups because car’s mode share is lower.
I also have some doubts about the reasonableness of the dwelling comparisons. Apart from being only 4 km from the CBD, the suburban apartment block used for the analysis is the Office of Housing’s K2 development in Raleigh St Windsor, billed as “the most environmentally sustainable public housing development in Australia”. According to the authors, it uses 25% less energy than comparable apartment developments. They are so impressed by its passive cooling design that they attribute no active cooling costs to it, a courtesy they don’t extend to the other dwelling types. K2 easily outscores the others on operating and embodied energy. My worry is that it’s not representative of suburban apartment developments generally, most of which are provided by the private sector on a strictly commercial basis.
Where the authors seem to be on firmer ground is when they discuss the historical evolution of the typical greenfield house. They show the average floor area expanded from 93 m2 in 1950 to 238 m2 in 2008, while the average number of occupants declined from 3.7 to 2.5 (although 2.5 seems low for a greenfield location). Over the same period consumption of heating energy fell from 740 MJ m-2 to 158 MJ m-2. In fact operational greenhouse emissions fell significantly between 2000 and 2008, notwithstanding a slight decline in household size. Taking this one step further by interpolating from the accompanying chart, it appears the house is quite competitive with the apartments on a per m2 basis in terms of per capita embodied and operating emissions.
While they’re often exaggerated, there are issues with sprawl, so it’s important that policy is informed by salient and reliable research. However arguing that “inner city housing is more energy-efficient than 7 star suburban homes”, even if done well, is trite and doesn’t do a lot to advance the cause of good policy. The priorities should be to ensure all households — whatever their location, dwelling type and demography — pay their external costs (that’s what the carbon price is about) and that the tax system doesn’t promote inefficient levels of investment in housing. And universities who want their research to be taken seriously should make it available publicly so it can be evaluated, not just seek to get by on a media release.
Update: I’ve also looked in more detail at the housing aspects of this research.