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Environmental Impact of New Housing Development


Sufficient and affordable housing is a highly important social and economic goal, but development can also have significant impacts on the environment and people.

 

The lack of a systematic tool to assess the environmental impacts of housing development meant that the benefit of adhering to higher building standards with lower adverse environmental impacts was excluded from, or underestimated in, value for money and cost-benefit analyses.

 

This project designed just such a tool: Environmental Impact of New Housing Development – Appraisal Tool (ENHAT).

 

The tool is designed to support the outline business case stage of a project and to enable users to do optioneering by looking at what might happen if the housing was developed in different ways. They are also designed to work alongside other guidance, such as the HMT Green Book or the DLUHC Appraisal Guidance.


Approach


eftec, in collaboration with SQW and Daedalus Environmental, developed ENHAT and the user guidance to address:

  • What are the environmental impacts of housing development?

  • How can those impacts be quantified?

  • How can those quantified impacts be assessed in terms of the cost or benefit to society?

  • How can these costs and benefits be aggregated and communicated to help the user make better decisions about the location and design of new housing?


Scoping the impacts of new housing development

 

The environmental impacts were organised into stages of development: land take, construction, and use (occupation of the homes).

 

Each of these stages can have impacts on the environment and people locally, regionally, or even nationally. An impact pathway approach was used to link the development activity and environmental outcomes and impacts as shown below.



Quantifying the outcomes

The outcomes are quantified by using existing evidence and methods, and where these were insufficient, primary economic valuation research. In particular, new evidence was produced to understand:

  • Brownfield disamenity

  • Greenfield amenity

  • Recreational feature amenity

  • Air pollutant removal

  • Carbon sequestration

  • Habitat provision

  • Embodied carbon in construction

  • Energy use

  • Water use

  • Climate adaptation

  • Blue green infrastructure (a bundle of benefits)

Monetising the impact

Monetary valuation of environmental outcomes also used existing evidence and value transfer. In addition, bespoke evidence was developed for use in this project through stated preference methods for disamenity benefits (the value of removing disamenity from brownfield development).


Conclusions


The ENHAT tool and guidance provide an approach to quantify and value the social and environmental impacts of new housing development.

 

The examples provided within the guidance demonstrate that these impacts can be very large.

 

They also show adopting better standards can significantly reduce negative impacts and enhance positive ones.

 

We hope this evidence and the ENHAT tool will be used to influence decisions about where and how to build new homes for better outcomes for all.


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