We have confirmation that tower blocks are energy inefficient. This might not come as a great surprise but a new study by Professor Philip Steadman at the Energy Institute, University College London, has shown that office and residential buildings use more energy in operation, per square metre of floor area, the taller they are.  The findings have been published by Create Streets.

The research was divided into four parts:

1. An analysis of operational energy use in some 700 UK office buildings of varying height

2. A statistical analysis of operational energy use against height of all residential buildings, grouped at the level of neighbourhoods, in twelve London boroughs

3. A study of the relationship of built form to density 

4. An analysis of the possible physical causes of the observed increase of energy use with height, using computer simulation.

The only conclusion that might be surprising is the extent of the difference:

“Comparing buildings on 6 storeys and fewer (‘low-rise’) with buildings on 20 storeys and more (‘high-rise’), electricity use in the high-rise is nearly two and a half times greater than in the low-rise (a 135 per cent increase). The increase in fossil fuel use (by 40 per cent) is less marked. Carbon emissions are more than doubled going from ‘low-rise’ to ‘high-rise’. “

Many will then shrug in a defeatist manner and repeat that miserable old canard that high rise, for all its faults, is necessary to achieve high density. Steadman rebuts this claim:

“Many people believe that high densities can only be achieved with tall buildings. This is by no means true in all cases. Density is powerfully affected by built form. In the 1970s Leslie Martin and Lionel March showed that, all other things being equal, slab blocks could achieve higher densities than towers on the same sites; and that court forms could achieve higher densities than slabs. The ratio between the densities of the three types of form (courts: slabs: towers) could go as high as 3: 2: 1. Meta Berghauser Pont and Per Haupt have recently measured the densities of large numbers of Dutch residential estates and have provided empirical confirmation of these counterintuitive theoretical findings.

“A spreadsheet model has been developed in the present project, incorporating Berghauser Pont and Haupt’s ‘Spacemate’ tool. This allows the user to specify a total floor area for a building, and the size and shape of the site. The model then determines the number of storeys needed to accommodate this floor area in a range of built forms – either towers, slabs, courts or cruciforms. Plan depth, and the spacing between a building and its neighbours, can be controlled. The building form is shown graphically, and its position is plotted in the Spacemate graph whose axes measure Floor Space Index (density) and Ground Space Index (ground coverage).

“It is thus possible to work out, for a given site and a specified density, what range of built forms is available to the architect and developer. Given that the project has found large increases in operational energy use with increasing height of buildings, this density work shows how lower-rise buildings could in many circumstances reduce energy consumption without sacrificing density. Tall towers could be replaced with slabs or courts in many actual and planned developments in London, to provide the same floor area on the same sites. These options depend critically however on the sizes of sites.”

This point too is hardly a surprise when you look at all the wasted space surrounding a typical tower block.

Given the terrible expense of keeping a flat in a tower block warm in winter it is perfectly understandable that councils who spent huge sums to insulate such blocks with cladding regarded themselves as undertaking a moral crusade to save lives. Of course the potential unintended consequences are now all too apparent.  But if anybody was in any doubt about the flawed nature of tower blocks in terms of energy efficiency they should read this report.

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