Dev32 - Minor Applications
Policy DEV32 requires all development to contribute to the 50% carbon reduction target by 2034, against a 2005 baseline, as well increasing the use and production of decentralised energy.
The checklist below should be completed as part of the Design and Access Statement, and used as a guide for applicants bringing forward minor development proposals, providing prompts that can help achieve greater carbon savings. Information from applicants will also assist with future policy and strategy development.
DEV32 carbon reduction checklist for minor applications
Resource minimisation evaluation
- Are any existing buildings being reused?
- How are materials being reused or recycled from the existing building or site?
- What is the sqm of floor and existing walls (external and internal) that are being disposed of off-site?
- What is the sqm of roof surface being disposed of off-site?
- What new materials are being used to create the new building?
- Have materials been considered on the basis of carbon saving?
- Are you proposing to use local materials providers? If so, what materials are being sourced locally?
- Is timber being sourced from sustainable sources? If so, what accreditation scheme is being used?
- Chatham House: Making Concrete Change: Innovation in Low-carbon Cement and Concrete
- UK Green Building Council - Embodied Carbon Practical Guidance
Climate resilience evaluation
- Has the proposal been positioned and designed to make best use of solar aspect - has orientation and positioning influenced the proposal?
- Has passive solar gain been incorporated into your design?
- How has the development been designed to avoid overheating?
- Is the development resilient to high rainfall or flooding (inland or coastal)?
- Is water being re-used or collected onsite?
- What Biodiversity gains are being secured by the proposal?
- The Committee on Climate Change have recommended ceasing connection to mains gas for cooking and space heating from 2025 for domestic buildings. What energy/technology will be used for cooking and space heating, and what alternatives were considered?
- How has energy demand been reduced through building fabric design?
- Will building regulations thermal efficiency standards be exceeded? If so, by how much?
- What energy efficiency measures are being used in the building?
- What renewable energy technologies were considered at the design stage of the project?
- What renewable energy technology is being used in the proposal, and why were specific technologies not chosen?
- Is the proposal equipped to install electric vehicle charging points either immediately or at a future date?
DEV32 and replacement dwellings
For replacement dwellings to demonstrate carbon reduction, a comparison exercise needs to be undertaken that considers the impact of releasing embodied carbon from the existing dwelling, with the carbon cost of the replacement dwelling. Comparison studies have shown that to knock down and replace a dwelling - without reusing any of the materials onsite - takes up around 10 times as much carbon as retrofitting the existing building. Renovating and retrofitting energy efficiency measures are also more cost-effective than demolition and rebuilding.
Comparable studies use a 100-year time frame to calculate the carbon cost of a building - this includes both the carbon embodied in the structure and the use of the dwelling by the occupants. It is very difficult for any replacement dwelling to generate a net carbon reduction given the loss of embodied carbon from the original structure, regardless of the energy efficiency of the replacement dwelling, and that is because the vast majority of carbon cost comes from the construction, and not the use, of a building.
Energy efficient building using energy from one of the mainstream providers will generally emit around 500-700 kg per annum. This can be reduced significantly by changing energy supplier to a provider who only suppliers certified renewable energy.
Average amount of carbon embodied within an existing building is likely to be measured in the tens or hundreds of tonnes. In addition to the carbon cost of the demolition of an existing building, a replacement dwelling will incur an additional carbon cost in the construction of the new building, typically this will exceed the carbon cost of the existing dwelling due to an increase in building footprint.
A dwelling is proposed to increase in floorspace, by far the most effective method is to extend an existing building whilst renovating and retrofitting the adjoining original structure. The checklist below has been created to assist applicants in reducing the carbon cost of their project.
- What is the approximate amount of carbon embodied in the existing building? Detail what assumptions have been used to calculate the embodied carbon.
- Using the same assumptions, what will be the amount of carbon embodied in the structure of the replacement dwelling?
- Are any recycled materials or products being used in the proposal?
- What is the net increase in sqm of floor and walls (internal and external) in the replacement dwelling?
- What is the net carbon cost of replacing the existing dwelling (remember to subtract the carbon cost of any materials from the existing building being re-used in the construction of the new building)?
- What is the approximate carbon cost of using the existing building per annum? Electricity info: Carbon calculator
- What will be the approximate carbon cost of using the replacement building per annum?
- What is net difference in carbon (from operational use) per annum between the existing building and the replacement?
- Does the current building have an up to date EPC? If so, what thermal efficiency improvements are identified as part of the EPC?
- What options have been considered to improve the thermal efficiency of the current building?
- What constraints prevent you from renovating and extending the current building to achieve the same result as replacing the original dwelling?
- Are there any biodiversity gains being secure from the proposal that could not be achieved through renovation alone?
- What planning benefits are being secured by replacing a dwelling rather than renovation, retrofitting and extending of the original building?