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Defining Environmentally Sustainable Building Budgets

Determining whether a building is sustainable requires a benchmark based on scientific knowledge of the earth’s carrying capacity. Environmental budgets or targets can be used to evaluate or compare building designs or performance. We propose a method for deriving targets based on global population projections through the year 2100 to allocate resource consumption and pollution emission budgets equally to all the earth’s inhabitants.

This article appeared in the newsletter from the Committee on the Environment, American Institute of Architects, AIA COTE notes, Summer 2006.

By Hal Levin

We propose a method for developing budgets based on calculation of fossil carbon emissions, an indicator of carbon equivalents greenhouse gas emissions, contributors to climate change. We use scientists’ calculations of the capacity of the earth’s atmosphere to balance the heat entering and leaving the atmosphere as a result of all forces including but not limited to human activities. The overwhelmingly dominant human contribution to climate change appears to be the human impact on the global carbon dioxide concentration. For 400,000 years before industrialization, the global average concentration never exceeded 300 ppm. Since industrialization, it has risen from 285 parts per million (ppm) CO2 to approximately 380 ppm, with a steep climb in the past few decades. Climate scientists predict that our present rate of growth in carbon emissions will result in a global average of 700 ppm CO2. Most climate scientists agree that we should stabilize the concentration between 450 and 550 ppm by the year 2100 in order to limit global average temperature to a 2 degrees Celsius increase above current climate. A substantial amount of science is available regarding the potential impacts of this amount of warming, and the consequences appear rather significant but are hoped to be tolerable. In fact, a recent European Commission report says that even limiting global CO2 to 450 or 550 ppm will result in a 25 to 75 percent risk that global average temperatures will increase by more than 2 degrees Celsius.

Some experts argue that we can’t wait until 2100 and that we should shoot for 2050 or sooner to stabilize atmospheric CO2. From a practical perspective, that does not appear to be achievable at present. Neither the United States nor the developing countries are signatories to the Kyoto Protocol. The extremely rapid diffusion of technology in many developing nations and their substantially higher rate of population growth compared with the developed countries suggest that they will have to radically alter their current path. But until developed nations set an example and develop the necessary technology and the policy instruments necessary to effect the change, it is difficult for leaders of developed countries to request that developing countries curtail their growth in the distribution of higher standards of living through appliances, automobiles, and other consumption that is energy intensive. The prudent approach is to reduce anthropogenic carbon emissions as much as possible as quickly as possibly—probably considerably faster than contemplated under the Kyoto Protocol and the most advanced current planning in Europe.

The approach proposed here involves a number of assumptions that are either subject to revision as we obtain new and better data in the next decade or two. It also involves some choices that warrant further discussion and revision to improve their fairness to all affected parties as well as their feasibility. The basic approach was first described in 1992 report by the Dutch government agency Advisory Council for Research on Nature and Environment (RMNO). The report, Ecocapacity as a Challenge to Technological Development, was borrowed and applied in reports produced by the Friends of the Earth Netherlands that also estimated the carrying capacity of the Netherlands that became a model for several European countries and finally for a report on Sustainable Europe. These reports translated “budgets” for resource consumption and pollution emissions into national targets against which national reporting could be compared. These activities contributed significantly to the current model for carbon emissions trading that has become widely accepted in Europe and that functions in the marketplace the way emissions trading of various air pollutants operates in the United States.

The Process
There are five simple steps in the process as follows.

Define the capacity of the resource or sink in question. In the case of fossil carbon emissions, this is based on the best available models of the impact of carbon emissions on global climate and uses the assumption of a 450 to 550 ppm global average CO2 concentration.

Translate the total emissions that are believed “sustainable” into a per capita budget. In the case of carbon emissions, to achieve 450 to 550 ppm global average CO2 concentrations would allow emissions of 1 to 2 kilograms of carbon per person per day (kg C/p-d) by the year 2100 with an expected population of about 8.5 billion people—the latest UN population projection. Compare this to the current global average of 3 kg C/p-day and the U.S. average of around 17 kg C/p-d. Of course various sources of energy have different implications, with electricity from coal emitting roughly twice that derived from natural gas. Hydropower is closer to carbon neutral, although there are some emissions related to the development and maintenance of hydropower electricity sources. Solar photovoltaic can also be close to zero on a life cycle basis.

Calculate the portion of total emissions attributable to buildings. Using the latest Department of Energy data on the distribution of energy consumption by sector and our own data on components of building-related energy attributed to industry, transportation, and agriculture, we estimated that building related energy consumption (including “plug loads”) is about 40 percent of total energy consumption. Thus, each individual’s emissions must be 0.4 to 0.8 kg C/d-p as a “sustainable” budget. Currently 5 to 7 kg/p-d are associated with building energy use. This estimate could be refined but is not likely to change more than about 5 to 10 percent. It includes construction, use, operation, maintenance, renovation, and demolition or recycling of buildings.

Determine the portion of total building use attributable to each building type. Again, based on DOE data on the shares of total energy used by each building type, we used the present share of each building type and allocated it to each. This allocation could be refined by analysis of the degree of conservation and efficiency already applied and the amount of further reductions deemed reasonably feasible and achievable in each type. Energy per square foot consumption represents a wide range with health care and food retail at the high end and public safety, public assembly, and storage on the low end.

Finally, to derive a target for a specific building, the budgets of its users are applied. For example, for a school, divide the number of students, teachers, and staff who study or work at the school by the total number at all schools at the same grade levels in the country. For offices, the value could be based on workers or work stations, for a library it could be based on daily average users, for a retail establishment on the number of customers or customer hours etc.

The proposal presented here is to compare modeling data for building designs or data from monitoring of built structures with the carbon emission budget targets to determine their “sustainability” with respect to carbon emissions. Similar budgets can be prepared, as was done by the Dutch in the reports mentioned above, for consumption of various renewable and non-renewable resources as well as for various pollution emissions and for land encroachment. Targets are set for biodiversity loss, ozone depletion, copper consumption, cadmium releases, etc.

An elaborated version of the derivation and a number of relevant references are part of a paper I presented in Tokyo last September at the Sustainable Buildings 2005 conference and two papers presented at Healthy Buildings 2006 in Lisbon, Portugal, in June 2006. These papers can be downloaded from

Other resources include:
EnergiePortal: Climate change:

ASHRAE web site pages for sustainability: