In a Nutshell
As the client, you should commission an interdisciplinary design team and ensure that the design and delivery process is properly managed so that the team works in an integrated manner. You need to set low energy (and low carbon emission) design goals and performance measures and develop appropriate design strategies.
Over-riding objectives will be to ensure that the building orientation, form, layout, fabric, insulation, day-lighting/lighting, ventilation, heating and other systems work together. An integrated approach is desirable that addresses whole system design and not each system separately in a compartmentalised approach. It is critically important that the interaction of the site, the building, and the facilities it provides are examined at the project concept and outline stage.
This guide provides an overview of some of the major issues to consider when designing to achieve low energy consumption and minimise associated carbon emissions. However, the guidance cannot be used as a substitute for professional advice and you should seek advice from appropriately qualified persons for your project.
The following issues are addressed:
- Management of the design process
- Whole life cost
- The design team
- Develop an energy strategy and targets
- Management in use
- Site selection and assessment
- Building plan form and orientation
- Building fabric and thermal capacity
MANAGEMENT OF THE DESIGN PROCESS
Feedback from clients and designers emphasises the importance of the management of the design process to achieve a low energy and emissions design. Experience has shown that it is very difficult to design a low energy building without the appropriate management of the design and construction process. The following elements are critical to success:
Management and responsibility. It is essential to appoint a named person as the low energy champion. Responsibility for the process may be shared by the team, but it may also be necessary to appoint a project manager to manage the process. There is a high risk of the “low energy baton” being dropped or falling between the different team members as the project advances.
Energy strategy and targets. You should develop an energy strategy and set objectives and targets for energy consumption in the building. You may also set targets for each team member at each stage of the development, and receive regular reports on performance, to agreed timescales, as the project advances.
Informed client, design and construction team. Make sure you and your design team have sufficient experience to fully understand the principles and practice of low energy design.
Commitment from each member of the team to low energy design and to the goal of creating a sustainable building.
Integrated decision making. You must ensure close collaboration between your interdisciplinary team members. The design and construction process should be a continuous and sustained team effort.
Communication. Effective communication within the design and construction team will help ensure that team members work together. Hold regular project team meetings to agree goals, budgets and track performance.
Whole life cost
A fundamental principle of low energy building design is to consider the whole life cost of the building and not just the lowest construction cost. Whole life cost includes the cost of design, construction, operation and maintenance and can even include the personnel cost of those who work in the building.
The adjacent diagram shows the relative costs of designing, building, maintaining and using a building. The cost of design is a very small part of the whole life costs of the building, but provides a significant opportunity to reduce the cost in use, including improved productivity of the building users.
The design team
It is important to get the different design professionals – architects, engineers and others – working together from the outset. This is necessary to ensure an integrated design approach, where each member of the team is committed to achieving a low energy design and plays their role in delivering it. Through integrated design the focus shifts from a compartmentalised approach (team members only involved on a ‘need-to-know’ basis) to an interdisciplinary one.
Your requirements for a low energy building should be presented during the briefing stage of the project. This will outline the range and extent of low energy measures and the strategies you wish to take into account.
Develop an energy strategy and targets
It is necessary to draw up an energy strategy at the beginning of your project to help co-ordinate the various performance-related issues that impact on the design process, the building, and its management in use. The energy champion should identify which design aspects should take priority in the design management process. Such a strategy can also be used as a reference for checking the design as it progresses and finally checking the completed building through commissioning.
Objectives and targets should be set for energy consumption. However, setting targets against current norms may not be sufficient for achieving building life cycle benefits. Your targets should be ambitious but also realistic. It may be possible to incorporate many energy-efficient features at little or no extra cost if these are taken into account from the outset and placed in the context of the building as a whole.
Management in use
You should consider at the outset, how you envisage the building will be used and operated. Your team should design out potential problems through minimising plant and equipment, for example by using natural ventilation instead of air conditioning. This will help avoid installing more complex mechanical and electrical equipment. A technologically complex building will require greater management in use, and may be more prone to breakdowns. Your energy strategy should take the desired level of technological complexity into account.
Energy analysis and reporting
Energy analysis based on building modelling will help assess the energy effectiveness of the design options. Your design team should therefore include computer building energy simulation capability.
Site selection and assessment
Building on a new site provides an ideal opportunity to incorporate energy issues into the design. Appropriate building orientation can help minimise energy demands by making effective use of sun, light, air, and shading.
At the outline proposals stage you should look at issues such as the building plan and form, thermal capacity, daylighting, ventilation and other strategies.
Building plan form and orientation
The building form affects the availability of daylighting and the potential use of natural ventilation where this is permissible.
Building form and orientation can help minimise energy consumption by:
- taking advantage of daylight to help reduce the use of electric lighting, while avoiding glare and solar gain problems.
- minimising solar gain in summer and maximising useful solar gain in winter.
- allowing natural ventilation to take place.
Deep-plan buildings tend to be highly energy dependent. On the other hand, narrow plan construction is better suited to the application of natural ventilation and daylighting.
Research has shown that people in the workplace prefer natural light to artificial light. Furthermore, the effective use of daylight can help reduce energy consumption. This should be complimented by the use of artificial lighting to supplement daylighting and the lighting system should operate in response to daylight levels.
Building fabric and thermal capacity
Well designed and constructed fabric can take advantage of the use of daylight, solar gain, natural ventilation and free cooling, when these are desirable, but also avoid them when not wanted.
The thermal mass of roofs, walls, floors (slabs) and internal walls can help stabilise internal temperatures and influence temperature swings, while thermal insulation will help reduce heat loss and gain.
The building should also achieve an acceptable level of air tightness to allow controlled ventilation and eliminate draughts.
The use of natural ventilation is preferable, but this depends on your circumstances. Buildings can be designed to eliminate or reduce the need for air conditioning. Building form and orientation can be utilised to facilitate natural ventilation, while exposed thermal mass combined with heat removal by natural or mechanical means can help lower peak temperatures. Shading devices and heavy, insulated walls can reduce solar gains. Energy efficient lighting and effective control systems can minimise heat gains from lighting, while energy efficient office equipment can also reduce internal heat gains.
An alternative to natural ventilation is mixed-mode systems which, combine natural and mechanical systems for ventilation and cooling.
Check the design for occupant comfort under all weather profiles, with due regard for behavioural issues. Ventilation in cold weather is of particular concern – occupants are very likely to close windows and thus reduce ventilation rates below ideal if they sense cool air or undesirable air movement.
It is necessary to carry out building commissioning to make sure that the facilities and systems are working correctly. You will need to check compliance with design, the energy targets and other performance requirements. Reputable studies in the US have found that energy savings of 15 percent are achievable through building commissioning.
Your design team will identify the elements for commissioning. For optimising energy efficiency, commissioning will include building fabric, mechanical and electrical systems. In the case where the design requires interaction between the building fabric and the building services such as ventilation or lighting, commissioning is particularly important. Check the building fabric and elements such as windows, doors, ventilation paths and shading devices.
Building studies have found an average of 28 significant building deficiencies on new build projects. Not alone is commissioning a necessary stage in the design and construction process, it is also a very profitable exercise.
Further information and guidance
The Minnesota Sustainable Design Guide.
The Guide is a design tool that can be used to overlay environmental issues on the design, construction, and operation of both new and renovated facilities. It can be used to set sustainable design priorities and goals; develop appropriate sustainable design strategies; and to determine performance measures to guide the sustainable design and decision-making processes.
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