LSC

Design issues

Sustainability

Photo Voltaic Cells - click for larger imageCurrently the majority of energy in the UK comes from fossil fuels. However there are three key reasons that this will change over the coming decades.

  • Fossil fuels are a finite resource.
  • Security of the current supply of fossil fuels is diminishing.
  • It is now widely accepted that it is very likely that Climate Change is predominantly a man made phenomenon linked to the carbon released into the atmosphere by man made activities predominantly by burning fossil fuels.

The main driver to reduce energy comes from the lack of alternative energy sources to fossil fuels to meet the current energy demand. The evidence showing the link between carbon emissions and climate change has resulted in carbon emissions becoming the focus of attention rather than just reducing energy.


Building Carbon Emissions and Building Regulations

The requirements of the EU building Performance of Buildings Directive (EPBD) were changed at the beginning of 2006 to solely focus on carbon. In response to this the UK regulation now requires a reduction of around 25% in direct carbon emissions from a building designed to 2002 standards. This represented a significant structural change in the method of approaching Building Regulations compliance in the UK.

The following graph in Figure 1 demonstrates how building regulations may evolve over the coming years. The Government announced in early 2007 that residential buildings will be expected to have a zero carbon footprint by 2016. The recently released Code for Sustainable Homes provides a guide to how this is intended to be implemented. This represents what is proposed as the path to carbon neutrality. It has been suggested that the Code for Sustainable Homes may represent future changes to the Building Regulations.

Figure 1 – A possible progression of Building Regulations for residential and non-residential Buildings. This graph was created from the following sources; Residential – Code for Sustainable Homes, Non Residential – Building Regulations Part L consultation document July 2004


What is the Carbon Footprint of a Building?

A carbon footprint is the measure of impact something has on the environment through its carbon dioxide emissions to the atmosphere. The footprint analogy is used as it suggests something we leave behind, for generations to come.

For the purpose of the design and operation of colleges it is suggested that the carbon footprint be defined as the operational carbon emissions arising from the building during its operation. This assessment would not include carbon emissions arising out of the following:

  • Carbon embodied in the design and construction process
  • Carbon emissions from transport
  • Carbon emissions from consumables, food and waste

A more thorough carbon footprinting assessment would include these items.


Design Approach to Minimising the Building’s Carbon Footprint

Through a structured and holistic approach the design of a low carbon building should render better solutions. A significant benefit should be the engagement and commitment of the Project Stakeholders.

Low carbon design necessitates a holistic approach, it can not be developed in isolation. Delivering a low carbon design may mean it is not possible to meet the ideal performance in every area (e.g. acoustics, comfort, smoke control etc) and specialist advice should be sought early in the design process.

As a simplistic overview, the initial strategy should consider the following three primary levels of design approach. In designing a low carbon college, the team should not move on to next element until they are satisfied that every reasonable opportunity has been exploited in the current stage.

  • Orientation, Massing and Geometry (RIBA Stage B-C) – A building’s orientation, geometry and massing should be defined at the earliest possible stage in the design process to promote excellent day lighting and ventilation (if naturally ventilated or mixed mode) and to minimise cooling loads in summer and heat loss in winter.
  • Building Envelope (RIBA Stage C-D) – A low carbon envelope should be sought that responds to the local climate and solar profile, i.e. one that allows the sun in when desired and keeps it out when not thus minimising over heating, cooling and lighting loads and maximising comfort.
  • Low or Zero Carbon Technology (RIBA Stage D) – Low or zero carbon technologies appropriate to site location should be considered only once the geometry and envelope concepts have conceived.

These three levels of design approach have varying levels of carbon effectiveness. A simple method of assessing their effectiveness is to consider the kilograms of carbon saved per pound spent, either in capital or whole life terms. Designing the building’s orientation, massing and geometry is the most cost effective way of reducing a building’s carbon footprint and should be considered at the earliest opportunity in the design process. The more expensive methodologies in level 3 should only be applied after these fundamental design approaches have been exhausted.