Technical efficiency

The UK government’s Low Carbon Transition Plan, which was published in July 2009, announced targets to reduce Britain’s carbon emissions by a fifth by 2020. In view of the fact that nearly half of all energy consumption is related to the operational use of buildings, and in a bid to successfully meet this target, government guidance and legislation is putting emphasis on the need to improve the energy efficiency of buildings as a means of significantly reducing carbon dioxide emissions. In direct response to this, Corus Colors has launched a new technical paper – An approach to the design of cost effective low carbon buildings – providing guidance and advice on those practical measures that can be initiated at the design stage of any new building to improve energy efficiency and reduce associated carbon dioxide emissions.

When we take into consideration government legislation such as the Climate Change bill, which will commit Britain to an 80 percent reduction in greenhouse gases by 2050, there is more pressure than ever for the construction industry to address building energy as a priority, whether in the context of new build or refurbishment projects.

Addressing the energy performance of a building at its concept design stage can result in the finished structure’s operational energy demands being significantly reduced – helping to minimise its carbon emissions and saving money. While care always needs to be taken to avoid compromising the functional performance of a building, by considering energy reduction at the design stage you can achieve far more, and often at a comparatively much lower cost, than by leaving these considerations until later on in the build programme. Through, for example, the optimisation of building geometry and layout, within the constraints of the development site, designers can lay the foundation on which to develop a highly energy efficient building strategy that can then be used to inform the whole design and build process and thereby maximise benefits to the eventual end user.

There are a variety of considerations that need to be taken into account and reducing service demands is an one. Factors such as internal temperature and control parameters, ventilation, humidity and internal lighting levels all have a big impact on the service energy demand. Careful assessment of the requirements for a building’s internal operating environment can result in a significant reduction in energy demand and associated carbon dioxide emissions.

Priorities should therefore focus on minimising the demand for heating, ventilation and artificial lighting through a combination of efficient building design and energy conscious building use, for example, ensuring an office space is designed to incorporate natural light, reducing the demand for lighting systems, without creating excessive additional fabric heat losses.

Optimising envelope efficiency through minimising heat loss through the building envelope is priority in any building design – by considering energy performance at this stage, you can dramatically reduce the need for artificial heating systems along with the associated energy consumption. Designers should therefore seek to optimise design of the building envelope to balance heat losses and solar and lighting gains through detailed consideration of insulation, air-tightness, minimisation of thermal bridges and incorporation of roof lights.

Having taken the necessary steps to minimise both the demand for and waste of operational energy wherever possible, the next design priority should be to maximise service efficiency and focus on specifying the most energy efficient means of delivery of heating, lighting and ventilation.

The best choice of mechanical and electrical (M&E) plant varies from one building to the next based on individual building specifications such as roof height, requirement for ventilation etc. For instance, there are several technologies available for supplying heat to a building, such as blown warm air or radiant tube heaters. While each brings associated benefits in terms of energy reduction, these advantages will be realised to varying degrees depending on the individual building.  

Once a building has been designed to minimise its operational energy requirements, and incorporates efficient heating and lighting systems, carbon footprint reductions can be made by considering sourcing of energy from low carbon options.

Solutions available include perforated Transpired Solar Collectors (pTSC’s), photovoltaics, wind turbines, solar thermal panels and heat pumps. Whilst each of these requires an initial outlay cost, payback can often be relatively quick and often improvements will add to the overall or lease value of the building.

For example, a recent US based study by McGraw-Hill revealed that thermally efficient buildings command three percent higher rental rates and an average increase of 7.5 percent in building value. Alongside this, the study found that they can deliver a 3.5 percent higher occupancy rate and ultimately improve return on investment by an average of 6.6 percent.

In designing low carbon buildings, there is a clear hierarchy for the designer to follow. Initially this is to minimise the requirement of servicing,  then to optimise the building envelope, then to use efficient servicing strategies, and finally sourcing the residual energy requirement from, as far as is possible, a low carbon or renewable source. Not only will this enable designers and building owners to meet the minimum requirements for energy efficiency as stipulated by governing legislative requirements, but will also clearly result in direct economic benefits for building owners through reduced daily energy consumption and a building that commands a higher letting and sales value.

Ian Clarke is applications development manager for Corus Colors