Evidence Based Sustainable Design

Do sustainable buildings have to cost more than traditional buildings?  We argue – no, at least not in CAPEX terms.  They require more creative thinking and planning, but not necessarily money.  In all technical endeavours, costs are saved through an insight and understanding, by simplifying solutions rather than making them complex. Efficient buildings are no different.

Key objectives for sustainable buildings are:

  1. Occupant comfort
  2. Commercial sustainability
  3. Environmental sustainability

Integrated and evidence based design sets out performance criteria and the methodology of achieving these objectives.  It is the process of quantifying outcomes of design decisions; where solutions are validated by practical experience as well as building modelling and simulation.  This approach results in a built environment outcome reflecting an innovative blend of design and technology solutions which satisfy the project’s environmental objectives within its commercial constraints.

Evidence based design attempts to achieve an overall optimal built environment outcome.  It examines the interaction and interdependence of design and technology choices, rather than celebrating individual solutions at the expense of the overall outcome.

Integrated design is at the heart of evidence based design philosophy.  It considers the whole building rather than its individual elements in isolation.  It evaluates the interaction of these elements and their impact on the overall sustainability outcome, in particular the energy efficiency and the indoor environment quality.  For example, comprehensive consideration of passive design solutions at the earliest stages of concept development often opens up opportunities for the application of simpler and cheaper climate control technologies.  TheWangarattaHigh Schoolcase study illustrates high level of integration between building design and the renewable energy based climate control strategy.  This approach resulted in achieving exceptional environmental and commercial outcomes.

Figure 1: Illustrates the traditional approach to design development, where disciplines’ teams work on their individual components.  Figure 2 illustrates the integrated and evidenced based design approach where all teams interact and contribute to design and cost optimisation.

Sustainable Design

Figure 1: Traditional approach to sustainable design       Figure 2: Evidence based design

Figure 3: Illustrates the evidence based design process where efficient design is guided by the past experience, modelling and simulation which combine occupant comfort, as well as commercial and environmental outcomes.

Design Process Pathway

Figure 3: The evidence based design process path

Meeting Commercial Outcomes

Commercial outcomes are at the heart of our integrated design approach.  Integrated design is a means to achieving desired commercial outcomes while satisfying other project objectives.  Traditional performance metrics include capital and operating costs.  For commercial property owners other considerations, such as market positioning and rental premium, are equally important.  These in turn are strongly influenced by the building environmental performance, as assessed and certified by a green building rating scheme.  This additional requirement radically changes the economic equation.  Justifying rental premium and attracting quality tenants on the basis of a landmark building form or celebrity architect may not be enough.  Building performance has to justify client’s willingness to pay the extra premium.  Indoor environment quality and reduced outgoings are key client considerations.  As mentioned earlier these outcomes result from a careful consideration of a wide range of design variables.  The integrated design approach becomes the only viable method to successfully reconcile competing objectives of aesthetics, capital cost, operating cost and environmental outcomes.

In order to ensure the commercial success of a project, early stages of design development need to be informed by input from all disciplines and stakeholders.  The design team needs to develop a common understanding of the project’s technical, financial and environmental objectives at the earliest stages of design development.  This understanding has to be shared and accepted by all team members.  Meinhardt’s multidisciplinary team adopts an integrated design approach where the earliest stages of concept development become an opportunity for value engineering seeking to reconcile competing project objectives.  Previous project experience and building modelling and simulation provide the required quantitative evidence for the client decision making process.  In this approach engineering outcomes plug directly into the client’s financial model at the earliest opportunity.  Design and technology choices are guided by the overall building efficiency rather than showcasing particular solutions or technologies.  Less becomes more; simplicity and ingenuity of design sell at a premium.  Focus on the properly defined commercial outcome is central to the design development process leading to a sustainable outcome.

Integrated Design Strategies

Integrated design strategies aim to combine passive design solutions with the building’s services to create a bio-responsive building that provide optimal indoor environmental quality and high level of energy efficiency.  The building’s form and fabric is in consideration of its internal and external environment.  Integrated efficient building design requires all design team members to be involved in the design process from initial conceptual and abstract stages through to detailed design so that the aesthetic vision of the building can be reconciled with energy efficiency and indoor environmental quality.  Early design decisions such as building form and orientation, daylight control elements, daylight admission, shading, high performance glazing and natural ventilation can accomplish energy performance and indoor comfort outcomes.  Figure 4 illustrates the integration of different building elements.

Appreciating User Needs

Occupant comfort can be broken down into its key elements of thermal comfort (air temperature, radiant temperature, humidity and air velocity), visual comfort (glare control and daylight availability) and air quality.

Elements of thermal comfort explain the response of building occupants in terms of heat transfer mechanisms; however they do not take into account the interaction of the occupant with the built environment.  The principle behind adaptive thermal comfort is that the user will adapt to the environment and interact with the passive design elements in the building.  For example having the ability to move around the building and operate windows, louvres and shading to suit specific working practices.  Provision of thermal comfort in passive designed buildings and their impact on adaptive thermal comfort needs to consider the user interface with the building and consider the cultural context.  For example if occupants are restricted by a rigid and formal dress code, they may not be able to dress to suit the weather conditions.  User operability of windows and shading should not cause disruption to normal work practices, such as creating draughts or glare issues.

A good passive design will cater for the user interaction and operability with the building façade and ventilation elements.  In order to meet the requirements of both the conventional and adaptive models of thermal comfort, the building envelope must be designed to facilitate internal comfort conditions.

The level of daylight into a space will influence glare levels and energy usage attributed to artificial lighting.  Admission of daylight through windows and openings in the building fabric is also associated with the provision of external views, internal aesthetics and the connectedness the occupants feel with the outside.  All these factors influence the occupant comfort.  Large extents of glazing without blinds can cause discomfort glare to occupants.  If the level of daylight though glazing is not in consideration of the glazing performance, then with the provision of certain levels of daylight will come increased solar gain.  Therefore optimal passive building design is a well considered balancing act between daylight, glare and heat gain/loss.  These three factors must be optimised while providing a space that caters to the aesthetic amenity and liveability of its occupants.  Often a combination of active and passive features are used to optimise natural lighting in the space and reduce cooling or heating energy demand, such as through the use of daylight admission and coupled with lighting controls.

A design for natural and mixed mode ventilation will go hand in hand with daylight penetration, heat losses or gains and views; as natural ventilation is often achieved through operable windows, louvres and other openings in the building fabric.  Similar to the previous discussion on the interaction of factors that must be considered when designing for optimal daylight, designing for natural ventilation must also consider glazing performance which accounts for heat gains and losses into the space, daylight ingress and access to views as these three elements are interrelated and have a strong bearing on each other and ultimately the overall energy performance and occupant comfort of the building.

When outside temperature conditions or the internal activities of a building prevent it utilising natural ventilation, active mechanical systems are needed to meet the heating/cooling and ventilation requirements of the occupied space.  Therefore it is necessary to select a mechanical system that can be integrated with the passive design elements in the building, for example a radiant system.  Ideally the system should also have the ability to be integrated with available low grade energy sources and sinks to minimise operational energy consumption.

In summary, successful reconciliation of environmental and commercial outcomes can only be achieved by careful consideration of key design, construction and operational variables.  We argue that this can only be achieved by considered and comprehensive response to the design brief and external environmental conditions.  Early stage quantitative analyses form the basis of such a response.  Elements of the evidence emerging from such analyses have to be then translated into an integrated design response.  Past experience also suggests that integrating input from key stakeholders and design and construction team early at the concept development stage also reduces the overall cost of the project.

By Dr Mirek Piechowski

Head of Building Science & Sustainability

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