The aim of the latest Biffaward study was to compare over one year - 1998 - the resources used, the wastes produced and the emissions from each stage of the construction cycle from mineral extraction to waste disposal. But putting the idea into practice has proved far from straightforward.
"The one thing that can be said with certainty about the numbers is that they are wrong," confess the study's authors, Richard Smith of consultancy Viridis, Jeff Kersey of the Construction Industry Research and Information Association and Polly Griffiths of the Transport Research Laboratory.
But they do claim them to be at least within the right orders of magnitude, despite the numerous assumptions, omissions and estimations in their research. One of their key recommendations is for a permanent industry monitoring exercise to be established requiring standardised reporting of data to enable similar exercises to be undertaken more accurately at regular intervals.
The authors contend that their overall objective has been fulfilled - to provide a clearer picture of the industry's environmental impacts in a way that can allow policy-makers to make strategic choices.
The study takes a much broader definition of the construction industry than usual, stretching it from raw material extraction to include clients, owners and operators of buildings and providers of products and services such as lighting and wiring producers where they have a significant direct relationship with construction activity.
The big picture
While one of the aims of the study was to break down the industry's impacts in more detail, its findings about the big picture are just as striking. Some 275 million tonnes of new building stock accumulate each year in the UK. This figure, in the absence of any credible methodology for "weighing a hospital" was derived through a crude calculation of the amount of material resources the industry consumes. Some figures were derived using economic activity data as proxies with deductions for the amount of waste and emissions.
"This is starting to put real numbers on what has been speculation in the past," concluded Barrie Mould, technical director of the consultancy Atkins, speaking at the launch of the report. Knowing the amount of stock accumulated is crucial, he says, even if the calculation is inexact.
"Whichever way you look at it, it's a big number," says Dr Mould. Even though he feels more detail is needed, some implications are already obvious.
For example, with so much new build going on, business is set to boom for firms like Atkins offering facilities management services. From this perspective, Dr Mould says it is clear that issues such as the energy efficiency "locked in" to a building at the design stage become highly significant.
While the report did not assess energy consumption during building use, this is determined to a large extent at the design stage. He suggests buildings should be designed for upgrading to accommodate more energy-efficient heating and lighting technologies as they develop.
A key conclusion is that there is huge potential to reduce resource demand by designing buildings for longevity and ease of rebuild and refurbishment. By comparison, initiatives such as recycling and "dematerialisation" - thought essential to curbing resource use and landfill demand in the short term - can only dent long-term resource consumption.
"We need to see buildings being designed to last 100 years, not 50 if we are to start to reduce raw material demand and the waste streams of the future," Dr Mould said.
Tinkering at the edges
Mr Smith of Viridis concurs: "The mass-balance shows that recycling and dematerialisation are only tinkering at the edges."
In order to create this stock each year, around 420 million tonnes of resources are needed, two-thirds of which are primary resources. The material efficiency of the sector - comparing the resources consumed to the amount of stock created - is 64%. Opinions are divided as to whether this is a high or low figure but in a sense the debate misses the point of the exercise as it is of more practical use to have identified the hot points of resource consumption and waste outputs within the lifecycle.
The tables show the material and energy flows through the sector. Some 150 million tonnes of waste are produced every year from UK construction activity - equivalent to three tonnes per person per year. Much of the data came from the Environment Agency for England and Wales, with extrapolations for Northern Ireland and Scotland. The total excludes liquid wastes as the researchers were unable to find reliable data.
Some 60% - 90 million tonnes - of the waste total arises from construction and demolition activity, and around half of this is estimated to be recycled. In fact, this is likely to be an underestimate as the researchers were unable to glean reliable data about waste reused on site during construction.
One recommendation is for companies to log these amounts in future. The authors comment that the recycling rate could be significantly boosted if there were not an outlet for the 20 million tonnes of construction and demolition waste deposited on sites exempt from waste management licensing.
The remaining 40% of the sector's waste is ascribed to product manufacture, but virtually all of this comes from quarrying. If one accepts that this is an inherently wasteful operation, it points again to the need to reduce demand.
But the authors also argue that, "although the current economic conditions may not be favourable, a significant quantity of this material is, from a technical perspective, potentially reusable if properly managed." Indeed, the advent of the aggregates tax even at a relatively low level has boosted interest in markets for quarry "wastes" (ENDS Report 323, pp 29-31 ).
Using Government energy statistics and apportioning these according to manufacturing sales, the researchers put the energy consumption of the construction sector at 7.8 million tonnes of oil equivalent in 1998 - equivalent to nearly a quarter of total industrial energy use in the UK. This excludes the consumption of heat and light during the occupation of a building.
The authors acknowledge that the relationship between energy use and sales has its flaws. Nevertheless, the figures shed light on the most energy-demanding areas of activity.
Mineral extraction and construction product manufacture, including cement whose manufacture is particularly energy-intensive, account for around half of the industry's energy consumption. Most of the energy consumed is based on fossil fuels.
The construction sector uses a much larger proportion of petroleum products - over half of its total - as a fuel compared with industry in general.
One reason for this is that transport of products, materials and wastes, and transport within construction sites, accounts for a surprisingly high 40% of the total. Mr Smith says the results point to significant savings that could be made by improved transport logistics.
The researchers appear to have had considerable difficulty in calculating the greenhouse gas emissions of the construction industry. They resorted to apportioning average emissions to construction activities according to sales data.
They came up with a total of 29.3 million tonnes of carbon dioxide - which is a whopping 18% of the total for all UK economic activity. The picture is heavily dominated by emissions during product manufacture and mineral extraction (71%) and from transport (14%).
Embarrassingly, however, the analysis goes awry when the authors attempt a consideration of other greenhouse gases. The report ends up with the absurd conclusion that the industry's global warming impact from nitrous oxide, methane, HFCs, etc is an order of magnitude higher than that attributable to CO2 alone.
The situation reveals some of the hazards of number-crunching-based research projects: the conclusions are sometimes plain wrong but the errors behind them can go unnoticed. In this case, ENDS has identified a data error concerning emissions of nitrous oxide. The report puts the sector's nitrous oxide emissions at 625,000 tonnes - with no explanation as to how such emissions, normally associated with agriculture, might arise in the construction supply chain. In fact, the official UK statistics reveal that total N2O emissions in 1998 were only 186,000 tonnes, less than one-third of the figure the report attributes to construction activity alone.
Scenarios for change
Where the report is successful is in bringing home the daunting scale of the material flows the sector causes. The implied challenge is in assessing scenarios for change that might reduce these impacts.
Various trends and influences acting upon the construction sector are addressed in the report. These include external factors such as economic conditions, demographic changes, climate and geography.
One such trend is the demographic pressure for 3.8 million new homes on top of Britain's existing 21 million. The report points out that these existing buildings require significant refurbishment and repair, which is usually undertaken by small firms with "a traditionally poor performance in sustainable resource use."
Climatic trends, meanwhile, are forecast to lead to demand for more "massive" temperature-proof concrete buildings.
Trends within the construction industry itself are driven by stakeholder and client pressure and are generally said to be heading in the right direction for sustainability. The report concludes optimistically that "most major companies now appear to be aware of resource use and waste quantification and minimisation issues."
However, a negative trend is the astonishingly large amount of "rework" going on. Nearly a third of construction is estimated to be redone to correct poor workmanship. The problem is said to be compounded by skills shortages in the industry.
The construction design process is likely to hold the greatest potential for significantly improving resource efficiency. Computer-aided design software is rapidly accelerating the pace of change as it becomes easier to calculate the energy implications and other environmental trade-offs of various design options. Information and communications technology is also improving logistical efficiency.
But the report's overall conclusion is that sectoral initiatives by the Government and industry have so far focused on specific objectives and lacked coherence across the sector. They say the absence of a body that can take a strategic overview to identify the trade-offs and improved efficiencies is a "fundamental obstacle" to making significant progress to improve resource sustainability.
At the report's launch, Mr Smith said that the Government's Waste and Resources Action Programme is well placed to take forward the mass-balance work and identify strategic opportunities. He commented that WRAP should do more to improve resource efficiency. The proposal is timely given that the Prime Minister's Strategy Unit has just proposed a bigger role for WRAP on waste strategy (ENDS Report 335, pp 21-26 ).