BIM and Sustainability :
In today’s fragmented world of highly specialised expertise in narrow fields we risk losing sight of these aims. The paradigm of sustainability is simply an effort to bring these aims back into focus. Daniel Lindahl identifies five broad areas of focus for sustainable building…
What is Sustainability? At is simplest, living within your means, or not taking on debts you are unable to pay back. More broadly, for us all as a community (local and global) living in a way that has no adverse impact on our planet, i.e. living within our global means. It’s all about sensitive appropriate design. However, it needs a pragmatic approach as the path to sustainability may take several unexpected turns and the aims of sustainability are sometimes at odds with each other.
This article will deal mostly with good architectural practice, and will only touch on BIM where this facilitates good sustainable building design.
In 1972 Welsh architect Alex Gordon wrote about the need for “Long Life, Loose Fit, Low Energy”; Today this would translate to sustainability, flexibility and energy efficiency. His paper crystallised the counter-culture reaction to corporate excesses in the 70’s, and though largely forgotten today, helped bring the concept of sustainability into today’s mainstream thinking.
I have here identified these five broad areas of focus for sustainable building and will elaborate on them in more detail: context, labour, materials, operation and longevity. However, as there is no preset template for sustainable design this article is really more of a checklist of the aspects of a building project that should be considered with a view to achieving sustainable outcomes.
The Local Environment
Choosing the right site for the project is one of the most important aspects of a project. The building needs to fit in with the terrain so that cut and fill is avoided, minimised, and equalised to avoid the need to carry soil to or from the site during construction. There should be minimal disruption to natural water flows and the ground water table. This can be achieved through sensitive design where minimal paved areas which are highly permeable, and retaining roof water in tanks or dams on the site for garden or other non-potable use.
Careful assessment of existing flora and fauna where this is relevant is also necessary and existing vegetation and wildlife corridors need to be preserved where possible. It is important to analyse the local microclimate to make best use of the local breezes, sunlight, and rainfall for passive climate control as well as power generation. There are many buzzwords in this vein around the theme of sustainable design, such as “biophilia” and “green building”, but really it all amounts to building in harmony with nature.
The Local Community
A new building, its function, and occupants, also needs to exist in harmony with its neighbours. Sustainability requires a symbiotic relationship between the different parts of a neighbourhood. Shops, services, and other commercial enterprises function better if they complement each other rather than being in direct competition. Community well-being and harmony comes from shared values and sensibilities though this should not negate the need to challenge established and unquestioned norms from time to time.
The Local Infrastructure
Existing water supply, waste disposal, transportation network, power and telecommunication utilities are often inadequate for large projects and need to be augmented. In other areas these services can exceed demand. Fitting the projects location to services that already exist as well as adopting alternatives that reduce dependence on such services is an important aspect of sustainability.
I believe that in the future this is an aspect of town planning that can greatly benefit from BIM, through the integration of all the BIM databases for the various projects within a community.
The construction process needs to be carried out with minimal disruption to the surrounding community, and in such a way that pollution in the form of dust, silt and noise is reduced to a minimum or eliminated completely.
Site access, on-site storage of materials, means of moving building components in place, all need to be carefully planned to minimise handling time, effort, and cost. Some BIM-software programs are now capable of generating construction animations to explore alternatives for cranage and other site logistics. This is as yet little used in projects to date, but offers great scope for making better project planning decisions.
Existing Local Resources
Employing workers from the local labour pool for a project will reduce commute times, travel costs and the associated carbon emissions. It will also enhance project buy-in and support from the local community.
While procurement methods may seem to have little to do with sustainability, competitive tendering is by its nature adversarial and wasteful of human resources in the bidding process, and does little to foster harmony. It also encourages cutting corners and promotes a focus on short term gain, rather than the long term thinking needed for true sustainability.
Non-adversarial procurement methods such as negotiated contracts, partnering, alliances, are more collaborative and encourages all in the team to think about long-term gains.
It would seem obvious that building materials should be non-toxic. However, over the years more and more of the materials in common use have been found to be harmful. Among these are: lead, asbestos, arsenic, as well as many plastics still in common use such as BPA and PVC. These create high levels of toxic pollutants either in production, installation, or ongoing use. The pollutants are chemical wastes in production, off-gassing of paints and vinyls through their early life, as well as release of dioxins in fires or disposal.
There is currently strong debate about whether PVC should be banned, and some countries have already begun to do so. It is one of the most common plastics used in buildings, chiefly in the form of plumbing pipes, insulation, siding but also many other items. Of particular concern in all plastics is the use of volatile carcinogenic halogens, chiefly chlorine, bromine and fluorine.
Renewable building materials are mainly: timber, grass and palm-leaves (for thatched roofs), and fabric from natural fibres. Non-renewable building materials are: extractive minerals such as steel, copper and aluminium, stone, clay in the form of bricks and tiles, glass (from sand), and petrochemicals that go into plastics and synthetic fibres.
At its simplest level, renewable sources are preferable to non-renewable, but there are many nuances to this. Tropical hardwoods can almost be classified as a non-renewable material, since cutting them and bringing them to market causes widespread environmental damage and their regrowth is much slower than the rate of harvesting. Stone, clay, and sand are plentiful, so their use as building materials is not likely to ever cause any depletion, and their non-renewable status can largely be discounted.
Most renewable materials are subject to various forms of decay, mainly in the form of rot, insect attack, decomposition, wear, UV breakdown due to sun exposure, or dilapidation caused by gravity in sagging structures. If exposed to weather they usually need applied finishes to extend their service life. However, many of such applied finishes have a degree of toxicity, and the need to regularly re-apply the finish makes this a less sustainable solution.
Non-renewable materials are often more durable and usually do not need applied finishes. However, some of the softer materials can still be subject to abrasion due to wind, sand, rain, regular use, and dilapidation from earthquakes or subsidence, as well as corrosion in the case of metals.
The greater durability of non-renewable materials will sometimes tip the scales in their favour for a sustainable outcome.
Embodied energy can be thought of in two ways. Natural embodied energy is the energy stored in carbon-based products such as timber. This is generally beneficial for sustainable building as new growth plantation timber sequesters a lot of CO2 through photosynthesis and when it is used more new growth takes its place.
However, in the context of sustainability the term embodied energy usually means the energy input required first in the extraction: fuel for mining, forestry machinery, cutting; secondly in the processing and manufacture: production of metals from ore, steel sheet and beams from iron, cement from lime, bricks from clay, milling of timber; thirdly transportation costs; and last, the energy required to trim, work, and use those materials in the construction project.
These types of embodied energy, particularly transportation over great distances, are often a decisive factor in evaluating sustainability.
The extent of raw materials used in a project can be reduced significantly at several levels in their journey from nature to components in the finished building. With good foresight and planning waste can be minimized in the manufacturing process, in the extraction, the milling, and in the determination of optimal milled or manufactured unit sizes,
Similarly foresight and planning for waste reduction at the project level can be achieved through the architect’s determination of design dimensions and patterns to make full use of boards and sheets as marketed, and in the intelligent use of off-cuts in the project for smaller components. The only limit to this is the designer’s imagination.
Often builders burn all off-cuts in the project clean-up at the end of the job. This is a practice that needs to be eliminated, as it not only wastes resources, but creates pollutants.
One of the most critical aspects of sustainable design is in planning for low energy use in the ongoing operation of the building. A thorough evaluation of design options and materials used in regard to orientation, heat transmission, heat retention, natural cooling and ventilation, and daylighting, will assist in optimising the design.
Today’s BIM-software programs can greatly facilitate this. ArchiCAD has a built-in energy evaluation functionality with detailed calculations of heat transmission, and infiltration for all building operation types, materials, openings, shading devices, orientation and location. This program tool has direct links to all region specific climatic data, evaluating different HVAC options, calculating energy consumption, costs and CO2 emissions over a year.
Revit has conceptual energy analysis tools which give a broad analysis of the impact of various building forms. For more detailed analysis at the materials level there are also external plug-in programs available.
Renewable Energy Sources
With increased awareness of their harmful effect on our planet our dependency on fossil fuels (coal, oil, nuclear) is slowly changing.
Clean, renewable energy sources have been around for a long time. Long before electricity was harnessed for power, water wheels and windmills were used to grind flour and mill timber. Waterwheels evolved into hydroelectric power, the mainstay of power generation in the early days. Solar hot water generation has also now been in use for several decades.
Today’s resurgence of interest in clean energy sources has led to great developments in technology and advances are made in the use of clean wind powered energy, photovoltaic solar power cells, wave energy, as well as capping of garbage dumps to generate methane fuel from waste. There are also many new developments in the use of daylighting for offices and other deep plate buildings. By the means of light shelves, tubes, or other devices, natural day light is reflected and directed to all working areas, eliminating the need for electric lighting in the daytime.
There will no doubt be several further developments in all these directions. The aim is for communities to be self-sustaining in clean power generation, and we are finally getting to the point where this is looking achievable.
Climate Control Systems
Passive climate control defines systems that function without energy input, monitoring, or adjustments. Passive systems are the top priority when designing for sustainable building. This means incorporating all possible non-mechanical means to achieve a comfortable indoor temperature together with good ventilation. Depending on the climate, passive systems typically incorporate: thermal insulation, triple glazing, thermal mass, trombe walls, convection chimneys, evaporative cooling, breeze control, directional sunscreens, etc.
There are also several active climate control systems, most notably air conditioning. These cannot be regarded as parts of the arsenal for sustainable building due to their heavy use of electricity. However, there have been several noteworthy developments towards energy conservation among these, and today’s heat pumps are far more efficient than the AC systems of a few decades ago.
Other innovations in active systems include smart glass which can be electrically controlled to become opaque and block out light, intelligent building systems which sense the number of occupants in a space and adjusting the climate control accordingly, geothermal space heating which circulates water through boreholes up to 200m down into bedrock tapping the higher core temperatures at that level, and heat exchange ventilation systems which heat up the incoming fresh air with the outgoing stale air.
Operational Logistics and Management
For a building to continue to function in a sustainable manner all aspects of how it is being used on an ongoing basis need to be carried out with that vision in mind.
Its supplies should be locally sourced, and easily and logically stored and accessed. Waste disposal needs to be easily managed, making full use of recycling, composting, and reuse. The building’s passive and active systems also need monitoring and regular cleaning and maintenance.
A good passive system can easily be rendered useless through the occupants’ ignorance of its function. One good example of this is a case where the architect came back to a building after some time to find the daylighting system was not working as expected. The light shelf near the top of the windows, which was to reflect light back to the ceiling further into the building was now filled with a long row of books!
A complex design is rarely optimal. Good planning and design with open permeable spaces and related functional areas grouped together is usually best achieved through simple, easily read solutions.
This is where the ‘loose fit’ paradigm comes into play. When planning for a particular use it’s a good idea to always consider the possibility of future changed use. Make spaces slightly more than minimum requirements. Design more for optimising materials use and site use than for minimum functional use.
Accommodate future changed practices, the incorporation of new technology, and multi-purpose spaces. A narrow passage, for instance, is simply a dead transition space. With 0.5m extra width it can be a library. This kind of thinking should be applied in all space planning.
Plan for growth. Make provision for future expansion sideways and upwards. Bear in mind that property values always grow faster in the heart of our cities, and a building that will not accommodate growth and increased site density will become obsolete much sooner than expected.
Plan for full accessibility by all potential interest groups, not just for what current legislation requires. Disability standards are frequently updated, and it’s a good idea to do some private research and experimentation to discover what actually works.
Infrastructure Present / Future
Service runs within the building should be simple, well documented and easily accessed for future changes and maintenance. Try to also discover or anticipate any future changes to surrounding roads, transportation network and service grids.
For a long life it goes without saying that a building needs to have a sound structure, able to withstand use and weather without knocks, wear, dilapidation and aging. However, a sustainable design would also factor in the ease of dismantling the structure and other building components in the future, when demolition or alterations become inevitable.
In the 70’s many office buildings were erected with in-situ post-tensioned concrete beams and floor plates to achieve larger spans. Many of these would now be nearing the end of their useful life, but their demolition is problematic as the built-in stresses would be explosive and difficult to control.
Building codes usually cover this, though sometimes inadequately. Good sustainable design needs to factor in all potential risks such as fire, storm, or earthquakes, as well as other personal hazards like slippage, falls, and injuries.
What I have outlined above is what I would hope most architects would consider self-evident aims of good design for all time. In today’s fragmented world of highly specialised expertise in narrow fields we risk losing sight of these aims. The paradigm of sustainability is simply an effort to bring these aims back into focus.
I have only mentioned BIM in passing, but would add here that the collaborative nature of BIM is the perfect vehicle for restoring this big picture thinking to all the experts working on their specialised parts of a project, and serves to maintain that vision. Reference Daniel Lindahl