Green Buildings: Why and How to Build Them
John Straube
The
Problem
The construction and operation of buildings consumes about a third of the world’s energy consumption, and 40% of all the mined resources. Striving to make buildings more sustainable, while saving construction and operating costs, and improving health and occupant well being is not only possible and practical, it should be the goal of most architecture.
The environmental “problem” we face is an increasing population with increasing consumption per person and increasing damage per action. This can be placed in the context of an equation as
Environmental impact = population x consumption/person x damage rate/consumption
The world’s population continues to grow, and grow fastest
in the developing world. The best
estimates predict a doubling of population in the
Figure 1: World Population Projections (UN Population Division)
The fact that much of this growth will be in the third world is relevant because the standard of living (and the rate of energy and resource consumption per person) is increasing quickly in these countries. Hence, we will not only have 3 billion more people in 50 years, but most of these people will wish to consume considerably more per capita than presently. At the same time, many of the buildings constructed in the developed world in the last 30 to 50 years have a shorter useful service life than older buildings. For example, although a turn of the century solid brick home is still functional today, it is unlikely that a home built in the 1980’s will be sufficiently functional to still be in service in 2080. This means that many of the buildings that already exist in developed countries will need to be extensively rebuilt or replaced.
Whereas 30 per cent of the world population lived in urban areas in 1950, the proportion of urban dwellers rose to 47 per cent in 2000 and is projected to attain 60 per cent by 2030 according to a recent UN report. This increasing urbanization changes the types of solutions that will be required to allow us to build and live sustainably.
The environmental damage (i.e., ecosystem destruction, species extinction, and pollution) caused by our consumption is significant. Some consumption causes more damage than other types. For example, traveling to work with a large sport utility vehicle or pickup truck consumes more energy and emits more pollution than the equivalent trip by subway. The consumption levels of the Western world increased with our “progress” (e.g., we drive further to work and play than ever before), and the development path taken by developing countries is typically following the same path, i.e., more damage for many of the same activities (e.g., as Indians and Chinese become wealthier, cars are chosen for the same journey that would previously have been conducted by walking or taking public transit). The fact that 33% of the world population growth over the next 50 years will be in the emerging economies of China and India underscores the scale of this potential phenomenon.
If developing countries even come close to the developed world’s rates of energy and resource use on a per capita basis, the consumption and damage will increase much more quickly than the population, and environmental damage can be expected to increase five or ten fold above current levels.
The hope is that if the industrialized world can reduce its consumption and its impact it can demonstrate to the remaining ¾ (or more) of the world’s people how to avoid an environmental catastrophe.
The developed world, and
The solutions, like the problems, are complex and multi-disciplinary. Building professionals have a unique potential to make a significant contribution to the solutions, since they are the best prepared to deal with this complex socio-techno-economic problem. Better technology will help, but more will be achieved by changing the way we work, design, travel, build, and live.
Figure 2: Year 2000 Energy Consumption of Commercial US Buildings as a
Function of Year Built
Solutions
The terms “sustainable”, “green” and the like have become a part of many discussions, product advertisements, and everyday speech. However despite the growing pervasiveness of such terms, it is remarkable how imprecise and poorly understood the concept of sustainability is. It is also not widely appreciated how difficult it will be to move toward a sustainable society or how significant the required changes will be.
The United Nations Bruntland Commission Report is the source and inspiration for the popularization of the concept of sustainability. The definition of sustainable development given was:
“Sustainable development is
development which meets the needs of the present without compromising the
ability of future generations to meet their own needs. “
A more correct and rigorous definition can be found in most chemistry, biology, and even economics textbooks:
A sustainable society, process, or product is one that can be sustained
or continue to be produced over the long term, without adversely affecting the
conditions necessary to support those same activities in the future.
When applied to human impact on the environment, the conditions referred to above are the natural systems (e.g, soil, ecosystem, water, plants, etc). that provide all of our material and energy resources including clean air, water, food, etc. Applying this definition to that of a building:
A sustainable building is one that can be produced and continue to be operated
over the long term without adversely affecting the natural conditions necessary
to support those same activities in the future.
In more practical terms, this means that a sustainable building cannot, in construction, operation, or disposal:
1. consume no non-renewable materials that cannot be easily and harmlessly recycled and/or returned to nature
2. consume non-renewable energy
3. destroy natural habitat, bio-diversity or bio-mass
4. produce pollutants of a type or quantity that cannot be harmlessly broken down by natural systems
These are very difficult criteria to meet, and in fact require all aspects of human activity to be modified to meet them. For example, until steel is recycled in a non-polluting manner with renewable energy sources, then no steel of any type (including nails or screws) can be included in a sustainable building. Clearly we are very far from producing even a single truly sustainable building. However, to move toward these goals is easy and possible. A more useful goal would be to:
Use energy and material more effectively both in the production and
operation of buildings while polluting and damaging natural systems as little
as possible.
A reasonable measure of a green building might be one that is significantly better than similar, or average, buildings of the same size and type in the same area. Hence the question to ask of anyone claiming to have created a green building is:
1. Does it use less non-renewable energy to operate?
2. Did it use fewer resources to build?
3. Will it last as long as useful?
4. Does it produce less pollution and damage natural systems less?
In a remarkable number of so-called green buildings, the answer to few of these questions is yes.
“Green” buildings are simply good buildings in most ways. That is, they are:
· Energy efficient – in operation and in construction
· Resource efficient – in operation and in construction
· Non-polluting – in operation and production
· Durable – so that they can be used for a long time
· Adaptable for many uses – so they can be re-used easily
· Healthy – few chemicals given off, no mould, fresh air
· Beautiful and comfortable – so that people will want to re-use them and enjoy while doing so
Sustainable building ratings like LEED, BREAM, etc. use different methods, with unique advantages and disadvantages, to rate environmentally sound buildings.
Several aspects of green buildings must be considered
Site choice and modifications affect the energy and resources required to construct the building (e.g. the less modifications the less resource use). The type of site and the way in which the architect changes the site will have a profound effect on the local ecology, water run-off, building energy use and durability (by shading wind, sun and rain), etc. In cases where a building is being re-built or renovated, adding plants and animals may be a part of the strategy. Hence, a sustainable building design must include the site.
Transportation Planning is an important part of any building design, since transportation consumes as much energy (and creates more pollution) than the energy used in the building sector. Designing buildings that minimize the need for transportation and encourage the use of less polluting transportation modes (walking, biking, public transit, rail or ship vs truck, etc. can have a large environmental impact. The addition of day care and a shop for daily needs in an office building can, for example, help reduce the need for additional travel. The most important intervention in this aspect is better planning – higher density towns and cities are critical to a sustainable future.
Resource efficiency of non-renewable energy and materials. This includes water of course. Renewable energy and materials are the ideal goal, but one must be careful not to violate other principles. Requiring too many resources (e.g., requiring a huge amount of wood to do the job of a small steel column), or too much energy (e.g., adobe may be renewable, but it requires so much energy to heat an adobe building in a very cold climate that it may not make sense), or by generating energy with damaging systems (e.g., photovoltaics generate a significant amount of pollution and consume a lot of energy in production and transportation).
The energy consumed during the construction and operation of buildings forms a major share of total human energy consumption – if one includes community planning in the category of “building”, then buildings consume 50-60% of all energy, with transportation around 25-30%, and industry about 20-25%. Hence, energy consumption must be given serious consideration.
Recycled non-renewable materials, while often an excellent means of reducing resource use, may in some cases use more energy than a different non-recycled virgin material. The obvious example is steel, which is both plentiful and easily recyclable, but consumes so much energy in production that it is difficult to qualify it as a “green” material. Of course, an attempt to quantify materials as green is fraught with difficulty. Steel is a low-impact way to form roof decking in commercial construction. Open-web steel joists are often the most efficient way to span large distances, although wood and concrete certainly have their place.
The best way to assess resource efficiency is to count – the amount of materials, the amount of Joules, including all transportation impacts. Resources like ATHENA are available to make this type of assessment more manageable.
For some reason, health and indoor environment are often confused with sustainable buildings. While it is clear that healthy buildings will likely survive and be used for a long time, there is little other connection to sustainability. This author would suggest that all buildings, sustainable or not, should be healthy for the occupants. Perhaps the connection is that buildings that are healthy for the community, for the ecology, for people in other countries, as well as for the occupants are sustainable.
These attributes require one to consider more aspects in the design of a building than normally done, e.g.,
Material Life-cycle: a cradle to grave view of all materials, from resource extraction to material disposal/reuse including pollution created. The complexity of some materials and their life cycle is so high that this is often reason enough to avoid them.
Good Building Science: which means assembling building materials and systems in such a way that the enclosures controls heat, air and moisture so that a durable, energy efficient building is provided (even if made of, for example, natural materials that may have lower performance than substitutes) without using an excess of materials.
Building Life-cycle: Which requires a flexible/adaptable design to allows for possibilities for re-use of building for different functions, re-arrangement of building, change in energy sources, sustainable lifestyles, etc
The Process
Changing the process we use to design, construct and operate buildings is the most effective means of achieving more sustainable built environment. Technology will assist us in this, but is a useless tool unless applied properly by designers, builders, and occupants.
Although many improved processes can be discussed, the following addresses what I believe to be some the most important points: pet strategies instead of well-defined goals, irrational belief in a strategy instead of rational accounting of energy and resources, and assumptions that a particular design works rather than assessing successes and learning from failures.
Decide on Shared Goals
Declaring a goal of “creating a green building” is practically useless for achieving the same. Designers and clients (and ideally the community) should define specific shared goals or values that they wish to achieve in the building design and common definitions for the project (e.g., define “local” in the goal “use local materials”). This may include low operational non-renewable energy use, little ecological damage (or an increase in ecological diversity), or low pollution emissions, or very low non-renewable resource use, or local resource and energy use, etc. Generally, a whole range of goals can be defined and then ranked in priority through group sessions.
Choose Strategies
Given the design goals, a range of strategies can be
chosen. For example, it is at this stage
that photovoltaics (PV), wind power or co-generation can be discussed as
strategies to meet the goal of energy self sufficiency. Too often, designers choose a strategy and
force the design goals to fit to the need for PV or green roofs, or rain water
collection. Consider not only one
strategy or competing strategies but combinations of strategies in your
scenarios. For example, the combination
of PV and wind power as electrical generation can often make sense in
The most difficult part of choosing strategies is recognizing the synergies for a holistic or systems approach to building design. For example, the cost of wind-generated electricity is high and is hence often discarded, but if the use of fewer energy efficient appliances and daylighting are applied to dramatically reduce electricity demand, alternate power sources may make sense. Similarly, highly insulating windows are often rejected based on first cost, but if the cost savings reaped by smaller AC, boiler, fans, and duct sizes are considered, a building can often cost less and use less energy while improving comfort.
Develop Metrics
Given the goals originally set, measures of performance should be set. Good measures include total embodied energy (in GJ/m2), annual purchased energy use (in GJ/m2), total tons of CO2 produced (or preferably absorbed), etc. The most difficult goals to measure are pollution production in construction (since many materials and workers come from far way) and ecological impact. Nevertheless, setting goals without measurable targets has far less impact than no targets at all.
Measure Performance
If you can’t measure it, you can’t control it. It may be energy, resource use, or pollution. To assess strategies, the performance of various scenarios must be assessed. This often requires computer energy-use models, daylighting models, and other such tools. However, the most useful tool that a green architect can use is a simple spreadsheet program that accounts the amount of materials used, the total energy use of a building (for lighting, plug loads, air leakage, conduction).
It is critical that the resources consumed during construction be accounted for. The choice between linoleum and VAT flooring material can be debated, but the use of half of much of either is always preferred. Assessing the need for square footage is the largest source of savings. A 2100 sf house is always superior to an equivalent 4000 sf house. Additional and potentially unnecessary finishes (like linoleum over concrete, when stain and sealer may be enough), high embodied energy or distantly sourced materials (like chromed interior metal or Italian marble) can easily be seen as less sustainable when the choices are simply compared in a list.
Measuring performance is used iteratively during the design phase. One must find energy and structural engineers that can help assess multiple concept designs so that the optimal solution can be achieved. Developing a design that is then handed to an engineer for tweaking will not result in optimal buildings. Energy and material use must be considered often, early, and quantitatively in the design process.
Finally, the resulting building should be monitored, an audit of how much construction waste was generated, how many cubic meters of concrete consumed, and how much energy it actually requires to operate must be measured and documented if a building is to be declared sustainable.