Introduction

Adaptation - Design for Future Climate

Provided by Bill Gething: Principal of Bill Gething: Sustainability + Architecture

What, Why, When, How, Extras

 

What is it? 

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Accordia, Cambridge.

Climate Change poses two distinct design challenges:  

  • The first (mitigation) is to act to try to limit the amount of future change by reducing the emissions that are understood to be its root cause, notably from our use of fossil fuels.
  • The second (adaptation) is to recognise that change is inevitable and to design differently in response to that change.

The two are inextricably linked – the better we are at the former, the less the need for the latter. 

 

 

Why use it?

Our approach to building design is based on past experience of a familiar climate. We now know that the climate is changing so we can no longer rely simply on that experience.

Buildings last a long time and we must, therefore, change our design approach so that the buildings we construct now are able to cope elegantly with projected changes in their lifetime.

When to use it?

Unless designing very short life buildings (less than 10 years) and depending to some extent on location, the rate of projected change is such that the climate will be sufficiently different in a building’s lifetime that this difference will need to be taken into account.

However, different aspects of climate change will affect elements of the building (and its siting) over different timescales, Elements that cannot be sensibly upgraded later (like foundations) need to be dealt with longer term changes from the outset; others (like shading) might be catered for by way of a strategy for future upgrades.

How to use it?

Key points:

  • 'Climate' should not be confused with “weather”. It is perhaps most simply described as weather averaged over a reasonably long period, conventionally 30 years.
  • The latest UK Climate Projections (known as UKCP09) provide a huge amount of information for a number of climate variables, however, they are presented in quite a complex, probabilistic, form based on a range of three global emissions scenarios which will have significantly different outcomes but with no steer on which of these is most likely to occur. Whilst this is scientifically rigorous, it presents the industry and our clients with multiple layers of uncertainty that make decision making difficult. The process of developing consensus and “translation” of these projections into codes, regulation and guidance which are familiar to the construction industry has started but it may take some time for adaptation issues to be fully assimilated.
  • Not all aspects of climate that are of direct relevance to building design are covered in the full probabilistic projections included in UKCP09; wind and storminess for example. Other approaches to predicting the likely change in these are being developed by organisations such as the Association of British Insurers in collaboration with the Met Office but, again, these have yet to be assimilated into codes, regulation and guidance.
  • The headline climate impacts are that we can expect: hotter, drier summers; warmer, wetter winters; rising sea levels and an increase in the number of extreme weather events.
  • Impacts will be location specific. There is likely to be regional variation; the climate in different parts of the country will change at different rates and in some aspects this may lead to greater divergence than we are used to. Different places will also present different primary challenges; for example flooding may be a key issue in one location and (almost) irrelevant in another. Beware of universal solutions.
  • Take care that adaptation strategies do not work against mitigation strategies. There is no point in trying to solve an adaptation problem by increasing fossil fuel consumption, for example.
  • Not all problems are best solved by building design alone. “Soft” adaptation strategies may be more economical and effective. Changing working hours, for example, might mean that the building need not be used in the hottest part of the day, avoiding the need for air-conditioning.
  • Adaptation strategies for the existing stock offer huge potential.

Design procedure:

  • Step 1 - Comfort: Keeping cool internally: We have yet to understand the extent to which we will adapt to hotter temperatures ourselves. That said, hotter summers are likely to have the greatest impact on future building design if we are to avoid reliance on increased air conditioning. This is an area where tools to inform design decisions have already been developed, albeit using they 2002 Climate Projections. Design Summer Year hourly data is available from CIBSE to feed into building environmental design software to analyse how well a building will cope through the century for 14 UK locations. CIBSE are currently working to develop the tool to reflect the latest 2009 projections.
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     Accordia, Cambridge.

    Step 2 - Comfort: Keeping cool in external spaces: Consider the role of shade, from planting or man made structures; urban green space and water to reduce the urban heat island effect; and options for planting –whether to go for drought tolerance or to incorporate sufficient water storage for irrigation to support planting that increases cooling through transpiration.
  • Step 3 - Comfort: Keeping warm: Higher average winter temperatures will reduce average winter energy consumption and may affect the viability of heat reclaim devices. Cold snaps and the imperative of reducing energy consumption are likely to mean that high levels of insulation are still desirable.
  • Step 4 - Construction: Foundations: Although annual rainfall is not projected to change significantly overall, the distribution of rainfall between summer and winter will. Consider the extent to which shrinkable soils will be affected.
  • Step 5 - Construction: Structural stability and weather tightness: Increased storminess is not covered in the core probabilistic projections of UKCP09. Guidance is being developed by the Association of British Insurers and it is anticipated that the British Standards Institution will assimilate adaptation measures in due course.
  • Step 6 - Construction: Materials: Consider how materials may change their performance under a different climate. For example, brickwork which may provide acceptable resistance to driving rain at present in a particular location may become saturated if subjected to longer or more extreme periods of rainfall in wetter winters. This may have significant implications for internal insulation of existing properties (as part of a mitigation strategy for example) where joist ends may become colder, damper and thus more prone to rot than expected.
  • Step 7 - Construction: Work on site: Consider how hotter summers will affect conditions on site - will site accommodation be adequate, will conditions inside the building be acceptable under construction before the services are active, will we need a new definition of “inclement weather”?
  • Step 8 - Flooding: This is another area where guidance is being developed rapidly by the Environment Agency in response to changing weather patterns and increasing hard surfacing in urban areas that exacerbate extreme rainfall events. Consider the options of avoiding risk by sensible siting, resistance to flooding by permanent or temporary barriers and, as a last resort, resilience to recover from flooding events as quickly and painlessly as possible.
  • Step 9 - Drainage: SUDS systems are rapidly becoming the norm so that rainfall is dealt with as close as possible to where it falls rather than concentrating it and passing it onto create a more difficult problem downstream. Increased frequency and magnitude of extreme event will need to be allowed for as will opportunities to store water so that it can be used for irrigation or other non-potable uses.
  • Step 10 - Water shortage: We are already becoming familiar with the fact that parts of the UK are less well supplied with water than some Mediterranean countries – a combination of increased population density and higher per capita water consumption. Reduced summer rainfall will put increased stress on existing reservoirs that will increase the need for water saving appliances and more effective use of water such as grey water recycling and rainwater storage.

 

Related strategies

Mitigation Rainwater catchment Solar controls and shading
Flood-risk: building placement Night ventilation Flood resilience
Stack ventilation Flood resistance Site planting
Cross ventilation SUDS Water conservation

 

Conflicting strategies

Passive solar heating: direct gain Passive solar heating: indirect gain Passive solar heating: isolated

 

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