CARBON IMPACT – MEDIUM

Greenfield sites are generally plots of land that have not been developed or built upon previously. This could include woodland (see adjacent), grassland, or agricultural land. Greenfield sites should not be confused with the “greenbelt” which is largely protected from development.

A benefit of greenfield over brownfield sites is that they are unlikely to suffer from contamination issues from past industrial uses and have minimal clearance and demolition requirements which can have high carbon impacts.

However, consideration should be given to the potential negative impacts on biodiversity, reduced availability of green space, and carbon released due to soil disturbances.

RECOMMENDATION – This is a better option than developing on a greenfield site with woodland or a highly contaminated brownfield site. However, steps should be taken to minimise carbon released from soil disturbances.

CARBON IMPACT – MEDIUM

Brownfield sites comprise of land which has already been built upon or developed in some way, but is now available for another purpose. If there are minimal clearance or demolition requirements then this may be the lowest carbon approach.

Many brownfield sites are located in existing towns and cities which means that existing infrastructure such as transport and utilities may already be in place, reducing carbon impacts from new infrastructure development.

Often overlooked for brownfield sites, consideration should be given to protect biodiversity which can often be at higher levels compared to more ‘natural’ areas.

Although this tool is focussed on new build development, efforts should be made to refurbish existing buildings (retrofit) and reuse materials wherever possible, either on the same site or elsewhere. If the buildings must be cleared then efforts should be made to ‘deconstruct’ rather than demolish to allow as many materials to be reused as possible.

RECOMMENDATION – This is a better option than developing on a greenfield site with woodland or a highly contaminated brownfield site. However, steps should be taken to protect or enhance existing biodiversity and reuse existing materials/buildings wherever possible.

The average form factor of the proposed dwellings on your development is medium (between 2.0 – 2.5).

Improve the efficiency of the dwellings’ form to reduce upfront carbon impacts. Consider building more apartment blocks and terraced homes.

This is the option with the second highest upfront carbon. This option has an estimated 20% less upfront carbon than option 1 (steel frame) but has slightly more than option 3 (timber frame) and around 20% more than option 4 (I-beam).

The highest carbon elements within this build-up are: 1) cladding (brickwork), 2) wall structure (block) and 3) insulation (PIR). The cladding makes up over 50% of the total upfront carbon. Consider switching to a lower carbon cladding material to reduce your carbon impacts.

There are no additional carbon sequestration benefits from this approach.

The specification for this build-up from outside to inside is brickwork, 50mm cavity, PIR insulation boards, blockwork, plasterboard, plaster skim.

RECOMMENDATION – Consider switching the structure from blockwork to timber frame or I-beams; the insulation to a bio-based alternative, and the brickwork cladding to timber cladding or render to reduce the carbon impacts.

This option has an estimated 25% less upfront carbon than option 1 (steel frame) and 5% less than option 2 (blockwork). However this option has slightly more upfront carbon than option 4 (I-beam).

The highest carbon elements within this build-up are: 1) cladding (brickwork), 2) insulation (PIR) and 3) internal lining. The cladding makes up over 50% of the total upfront carbon.

The timber frame provides some additional carbon sequestration benefits, locking up an estimated 25 kgCO2e/m², which is one third of the total upfront carbon of the option. Further carbon could be sequestrated if a bio-based insulation such as woodfibre was used instead of PIR.

The specification for this build-up from outside to inside is brickwork, 50mm cavity, breather membrane, OSB, timber studs with PIR insulation and timber battens, insulated plasterboard, plaster skim.

RECOMMENDATION – Consider switching the insulation to a bio-based alternative, and the brickwork cladding to timber cladding or render to reduce the carbon impacts.

The range in upfront carbon figures for all options in this section are fairly close but this option has the second highest upfront carbon.

However, this option provides very strong additional carbon sequestration benefits, locking up an estimated 80 kgCO2e/m², which is double the total estimated upfront carbon. The majority of the biogenic carbon is in the roof structure and the insulation, with some in the timber roofing battens.

The highest carbon elements within this build-up are: 1) cladding (concrete roof tiles), 2) roof structure (i-beams) and 3) insulation (cellulose).

The specification for this build-up from outside to inside is concrete roof tiles, roofing battens and counter battens, breather membrane, OSB, cellulose insulation between I-beams, OSB, vapour control layer, service void with timber battens, plasterboard, plaster skim.

RECOMMENDATION – The carbon sequestration benefits from this option are very significant and the highest upfront carbon element is the cladding. Consider switching to a lower carbon roofing tile material such as natural slate tiles to reduce the carbon impacts of this option.

Despite the use of aluminium this option has the second lowest upfront carbon – over 50% less then Option 1 (Aluminium).

This option provides additional carbon sequestration benefits, locking up an estimated 20 kgCO2e/m².

RECOMMENDATION – Consider switching to a lower carbon option such as timber frame windows to reduce impacts further, whilst still retaining carbon sequestration benefits,.