You can’t assess the Sustainability of Tall Buildings on a per building basis

A lot of nonsnse on twitter about the sustinability of tall buildings, following this article in the Guardian by Rowan Moore

The engineer Tim Snelson, of the design consultancy Arup, has just blown a hole in any claim they might have had to be environmentally sustainable. Writing in this month’s issue of the architecture magazine Domus, he points out that a typical skyscraper will have at least double the carbon footprint of a 10-storey building of the same floor area.

He is talking about the resources that go into building it, what is called its “embodied” energy. Tall buildings are more structurally demanding than lower ones – it takes a lot of effort, for example, to stop them swaying – and so require more steel and concrete. 

Snelson is correct but that is not the way to solely assess energy use, because people working in a tall building have o travel to work, as do people living in them.

If you build a two storey building one apartment each floor that is one less one storey house elsewhere you have to build. The sustainability case for tall buildings is that they enable compact central city places of work or housing with high cpacity mass rapid transit serving them. The more of them you build the smaller and more compact the city can become and the less car dependent sprawl you have to build. Also it takes up less space which also has an opportunity cost. Consider if Canary Wharf was built at two storeys. It would take up the whole of the Isle of dogs and take up the space of what is now planned as 50,000 houses. Image those 50,000 houses werent planned, you would need another Harlow somewhere in the South East of England.

Optimum Size of New Settlements in The Arc – Some History

When Ebenezor Howard was writing Garden Cities of Tommorrow he thought about their ideal size. He took as a model a reasonably well functioning small English Town, with its own school, hospital etc, and decided on Hitchin. Which had a population of around 20,000 in 1900, and around 35,000 now (declining then like most market towns, till commuter growth to London took off in the 1930s). Howard assumed a maximum population of around 32,000 for a Garden City so may have assumed continued growth at Htchin.

One thing I discovered was that Howard’s assumptions were based on the high household size of the time, and even at the relatively high densities he assumed in his book (as opposed to the lower ones designed by Unwin) it was not possible to fit five walkable schools into the catchment of a single secondary school or station, with modern family sizes) unless you increased the density to over 100 DPH, or had a polycentric form.

The Abercrombie Plan had a number of quite small new towns. For example Beconsfield only had a population today of 12,000. Some of the new Towns such as Stevenage were enlarged several times from their original design size.

By the mid 1960s lessons were being learned from the first generation of New Towns. The most successful were the lragest ones with the best transport connections. The Treasury pressed for the third generation of new towns – Milton Keynes and Telford – to be much larger, new cities of around 1/4 million design size, not just new towns.

I think the Treasury at the time were influenced by the first modern thinking in regional science emanating out of France. Growth pole theory suggested you would get higher economic growth from urban economies of scale from larger settlements. This has been borne out by history as for many years MK has been Britain’s fastest growing town.

Apparently Homes England have signaled they wish to see larger Garden Communities – of around 10,000. For the Arc they have said at conferences they are looking at 50,000 minimum. 10,000 is an arbitrary number. You need to think in terms of units a settlement around multiples of a primary school then secondary school. For a typical five feeder school secondary and typical pupil yields that equates to around units of 12,800 population.

Then you have the problem that Oxford and Cambridge are structurally very difficult cities to expand, with many benefits from quality of life, access to open space, walkability and cyclability owing to their compact nature. Once the current local plan round of growth is over there will be only limited opportunities to grow on either cities edge. There certainly is not a case to grow from there currently populations (around 150,000) to MK size (250,000), on the other hand you could grow MK to 1/2 a million (if you include adjoining areas in Bucks and Beds) and that is the ambition. Though not necessarily with the support of Central Beds or Bucks.

So even this crude calculation suggests a crude broad ‘landing zone’ for new settlement design size in the Arc. Grow MK by an MK, and to protect the compact form of Cambridge and Oxford, grow another Oxford and another Cambridge nearby – within short transit distance. That makes up around half of the 1.5million needed. The rest going on growth in Northamptonshire and the rest of Bedfordshire, as well as growth around smaller settlements across ll four counties.

This is managable and avoids the much worse alternative of scattered shotgun like pot shots at every village you see in call for sites.

This is not ‘concreting over the countryside’ it is its very opposite as a conventional local plan driven approach would produce. If you argue against that you are arguing Oxford or Cambridge should never have been built. Each takes up only a tiny front print of the huge arc area and the alternative would be massive sprawl. The new towns like old Oxford and Cambridge would demand their own Green Belts to ensure they dont sprawl beyond their optimum design size. Nor would they be huge estates of car orientated development, as we see for example in Northampton. International nest practice suggests a string of pearls approach based around transit orientated development (15 minute neighbourhoods) feeding into a dense urban core – much like Fred Pooleys original – but never built, plan for MK.

The ‘Virtual AONB’ of the Cambrian Mountains and Windfarms

The Cambrian Mountains (and severa smaller areas in wales) were recommended as National Park or AONB by the commission that made recommendations on all National Parks/AONBs in 1948. They were never designated. They were proposed again in 1965, opposition was such, even coming from the Campaign for Protection for Rural Wales, that the Minister dropped it without even an inquiry. Since then campaigners have sought an AONB, though Welsh Ministers have sought to avoid even addressing this issue. The objections though are similar to those to the Cairngorms National Park and North Pennines AONB, which two generations late were eventually designated.

However the key issue in planning terms is the lack of ‘the presumption against major developments’ test – which means no windfarms.

However the welsh government has commissioned a national landscape character assessment for Wales which grades the quality of everywhere. And this was used to ‘pre-assess’ areas for utility scale windfarms, and excludes the Cambrian mountains. So the AONB sort of exists in ghost form in the new Wales National Plan.

Im sure Boris would love the Welsh government to finally declare it as then he could reach almost in one fell swoop his international commitment to designate 30% of the UK as protected. Im sure a side deal could be done as part of the South West Metro connection to Bristol as part of the Hendry review – or somesuch.