Strategy for low emission refurbishment

In this exclusive extract from The Handbook of Sustainable Refurbishment: Non-Domestic Buildings by Nick V. Baker, we look at the opportunities for reducing emissions offered by building refurbishment.

The case for low emission refurbishment: Energy use in buildings

In the non-domestic sector in Europe, building refurbishments offer far more opportunities for reducing emissions than new building; the latter represents annually less than 1.5 per cent of the building stock. The usual motivation for refurbishment includes:

• Replacement of degraded finishes and components
• Tailoring space organization to new uses
• Improving environmental quality.

These reasons may be sufficient in themselves to justify the cost. If at the same time the building can be made more energy efficient, there will be a reduction in running cost and a reduction in CO₂ emissions. This will often be at a modest extra cost that can be justified by reduced running costs, or in some cases even, no extra cost.

Refurbishment versus rebuild: Economics and environmental impact

There are many instances when demolition and rebuild will be considered as an alternative to refurbishment. This could be justified purely on economic grounds, or the advantages offered by a new building could be considered to justify the extra cost. However, two non-economic factors should be considered:

1. The environmental impact of refurbishment versus newbuild
2. The socio-economic impact.

Initially, the environmental impact of refurbishment will almost always be less than demolition and newbuild. This is because all the materials carry embodied energy – to replace them causes new carbon emissions. Furthermore, the demolition process and waste disposal creates carbon emission as well as other waste disposal impacts. It is often argued that a new building will operate at higher energy performance than a refurbished one, and that during its lifetime, may have less environmental impact. Two important effects should be considered – that newbuild is only the lowest emitter after the break-even time period, and that this period can be extended by improved performance of the refurbished option. Also, if the break-even time is beyond the time of the environmental crisis (or emission reduction target), the life-cycle emission is irrelevant and the refurbished building is the best choice. It is also evident that the break-even point is sensitive to the actual performance of the buildings; new buildings have not in general performed as well as predicted and this will postpone the break-even point.

The second consideration is about social benefit and employment. Generally, refurbishment carries a higher proportion of labour cost than newbuild. For example, the repair of a concrete structure and the cleaning of concrete finishes will direct money to tradesmen that in the case of new build would go to investors in concrete and steel manufacture.

Implications for change of use

Refurbishment is often accompanied by change of use. This may be across recognized use types – for example a nursing area of a hospital becoming an administrative centre, or a change from residential to office use. Or it may be that within a use type the functional demands on spaces are changing due to reorganization and the impact of changes in practice and technology. For example, developments in IT have a continuing influence on office practice and the spaces that support it. It is difficult to generalize here, but it could be said that opportunities are sometimes missed because designers impose stereotypical solutions, often ignoring the serendipity of fitting a new function into a building generated by a different set of aims.

For example, in a conversion of an old factory workshop to modern office use, high ceilings with exposed structural slabs are often replaced with suspended ceilings for acoustic reasons, and under the misguided impression that the original spaces would be impossible to heat efficiently. This action not only destroys much of the architectural quality of the space, but will also have a negative influence on daylight distribution, natural ventilation and, possibly, thermal response.

Change of use may bring about changes in purely technical parameters. These include:

• Occupancy pattern and density
• Internal gains
• Lighting levels
• Ventilation rates
• Thermal set-points and response
• Acoustic properties (reverberation time, noise exclusion).

These changes may bring about benefits and disbenefits. For example, an historic warehouse converted into a library will create a difficult challenge to the designer if the intention is to provide daylight, due to the shallow floor-to ceiling height. On the other hand, a heavyweight building that required wasteful intermittent heating in its original function as a primary school, would not be so inefficient if used for a much longer occupied period as, for example, a health clinic. Furthermore, the intermittent heating would be less wasteful anyway if the envelope insulation was improved as part of the refurbishment package.

Thus, the inherent properties of the building, the operational requirements of the new use, and the technical options in the refurbishment all have to be considered interactively.

Impact on energy consumption

In spite of improvements to the performance of the fabric and systems, change of use may bring about an increase in the energy consumption. This does not necessarily mean that the low energy refurbishment has failed, since the measures adopted have undoubtedly led to lower energy consumption than if absent.

In measuring the success of the refurbishment then, it would be fair to make a comparison of the building's actual energy performance with, firstly, the existing building under the new use and complying with accepted comfort conditions, but without adopting low-energy measures. Secondly, a comparison should be made with a new building of similar use type. We might expect a performance somewhere between these two or with really successful refurbishments, even surpassing typical newbuild performance. Finally, a comparison should be made with the average emissions for the building stock of the same use type. As an example, a refurbished building emits 35 per cent of that predicted for the original building with a change of use, and 58 per cent of that of the measured average for the existing building stock, although it emits 10 per cent more than a new building. The fact that the refurbished building with its new use emits nearly twice that of the original building with its original use, is not of much relevance.

Find out more

The refurbishment of existing buildings is a neglected subject within sustainable architecture: attention is usually focused on new buildings.

Old buildings can use large amounts of energy and provide poor internal conditions for occupants. They may have high heating demand, poor lighting, poor ventilation, solar penetration and glare, and poor control of heating and cooling. Demolition is an option but the alternative of refurbishment is starting to be seen as more sustainable in terms of architectural value, materials use, neighbourhood disruption and waste disposal.

Building new is more carbon intensive and carries many wider environmental impacts. In addition, the potential impact of low energy refurbishment is much greener than that for new build since there are many more existing buildings that will be built in the next 10-20 years, the period over which many CO₂ emission targets apply.

This handbook offers architects, engineers and a wide range of building professionals practical advice, illustrated by real examples. It moves from principles of sustainable refurbishment to specific design and engineering guidance. It emphasises the need for an integrated approach by showing how refurbishment measures interact with one and other, and with the occupants, and how performance is ultimately influenced by this interaction.

To order a copy of this book, please visit RIBA Bookshops.

Published by Earthscan in association with RIBA Publishing. Copyright Earthscan September 2009.

Related NBS information:

Articles:

• Management of the indoor environment
• Healthy, efficient and sustainable buildings
• Sustainable property - does it make economic sense?

Selected links:

• Green building
• Sustainable development

Added February 2010

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