Policy CC/DC: Designing for a changing climate

DRAFT version for various committee meetings.

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What will this policy do?

This policy will set out how the design of developments should take account of our changing climate, for example extreme weather events such as heat waves and flash flooding. 

Proposed policy direction

All new dwellings must be designed to achieve a low overheating risk using the Good Homes Alliance Overheating in New Homes Tool and Guidance, with more detailed modelling required for schemes identified as being ‘at risk’, using future climate scenarios such as those provided by 2050 Prometheus weather data for Cambridge. 

All non-domestic buildings must be designed to achieve a low overheating risk using the cooling hierarchy, with more detailed modelling required for major developments using future climate scenarios such as those provided by 2050 Prometheus weather data for Cambridge. 

All developments should take a design led approach to climate change adaptation with approaches integrated into architectural design.  For overheating, proposals should follow the cooling hierarchy as follows: 

  1. Passive design: minimise internal heat generation through energy efficient design and reduction of heat entering the building through consideration of orientation, overhangs and external shading, albedo, fenestration, insulation and green roofs. 

  1. Passive/natural cooling: use of outside air, where possible pre-cooled by soft landscaping, a green roof or by passing it underground to ventilate and cool a building without the use of a powered system.  Cross ventilation, passive stack and wind driven ventilation should be maximised and single aspect dwellings must be avoided for all schemes as effective passive ventilation can be difficult or impossible to achieve.  Windows and/or ventilation panels must be designed to allow effective and secure ventilation. 

  1. Mixed mode cooling: with local mechanical ventilation/cooling provided where needed to supplement the above measures using low energy mechanical cooling 

  1. Full building mechanical ventilation/cooling system, ensuring the lowest carbon/energy options and only considered after all other elements of the hierarchy have been utilised. 

All development proposals must utilise site wide approaches to reduce climate risks, including the integration of sustainable drainage systems as part of landscape design, the use of cool materials and urban greening, for example through increased tree canopy cover and an enhanced treescape and integrating green spaces into new developments. 

Why is this policy needed?

The Planning Act requires Local Plans to have policies related to climate change mitigation and adaptation.  At the same time as reducing carbon emissions, we must not lose sight of the fact that our climate is already changing as a result of past emissions.  Extreme weather events including flooding and heat waves are now becoming common place, and as such we need to ensure that all new developments are adaptable to this changing climate, in ways which do not energy use and associated carbon emissions.  Overheating, particularly in new residential buildings is becoming an increasing problem with climate change, with potentially serious consequences to health and life.  Overheating risks can and should be mitigated through consideration of various factors at early design stages at low or no cost. 

Analysis from the Committee on Climate Change has shown that a lack of adaptation measures in new homes built in England over the past 5 years has led to many new homes not being resilient to future high temperatures.  This will require costly retrofit to make them safe and habitable. They recommend that planning policy must change to ensure that further homes are not locked in to increased climate vulnerability.  In addition to policy CC/DC, policy CC/FM gives consideration to flooding and sustainable water management.  There are also links to our design policies in the Great Places chapter, in order to ensure that measures to reduce climate risks are integrated into the design of new developments from the outset. 

What consultation have we done on this issue?

Feedback received during the First Conversation consultation included support for policy related to overheating in new developments.  There was support for an approach that requires developments to respond to the most up to date risks identified by the Climate Change Committee and that demonstrates a clear adaptation strategy. We should take account of more frequent and intense flood events and water stress in the region. Adaptation policies need enough flexibility to accommodate and adapt to the fast-paced evolution of technology.  Guidance on retrofitting adaptation measures would be welcomed.

What alternatives did we consider?

No policy, rely on national guidance – Not considered a reasonable alternative, as local planning authorities have a legal duty to include policies related to both climate change mitigation and adaptation, as contained within the Planning Act. 

Existing policies in adopted 2018 Local Plans

South Cambridgeshire Local Plan 2018 

  • Policy CC/1: Mitigation and Adaptation to Climate Change 

Cambridge Local Plan 2018 

  • Policy 28: Carbon reduction, community energy networks, sustainable design and construction, and water use 

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