School of Specification Introduction to the Urban Greening Factor – ADC

What is the Urban Green Factor (UGF) and why is it important?

The Urban Greening Factor (UGF) is a tool for evaluating the quantity and quality of urban greening provided by a development proposal. It became part of the London Plan Policy G5 in 2021, with the aim of ensuring better planned and better quality greening interventions for the capital’s hard working green infrastructure network.

How should the UGF be integrated into the design process?

It should be key consideration at the start of the design process and part of a holistic landscape-led approach, where buildings work to support quality landscape instead of retrospectively accommodating landscape and habitat around them. Early engagement with a landscape architect is recommended to ensure every practical opportunity is explored to achieve maximum UGF scoring. Professionals should utilise local and regional green infrastructure plans, maps and resources to maximise greening potential and deliver urban greening solutions that are relevant to the site and its needs.

Early engagement with a landscape architect is recommended to ensure every practical opportunity is explored to achieve maximum UGF scoring”

How is the UGF calculated?

UGF sets out weightings (factors) for each surface cover typology on a project. These are scored from 0-1 based on their habitat potential and their contribution to natural eco-systems, and are set out in a calculator that can be downloaded from the database of the relevant planning authority. As the design progresses, the anticipated area for each surface cover type can be fed into the calculator to assess the UGF. Within the calculator, the area of each surface type is multiplied by its factor. The collated score is finally divided by the total site area to calculate the overall UGF score.

What are the pros and cons of different UGF factor values?

The UGF factor values for each surface cover typology are generally arranged with depreciating values as follows:

• Semi natural vegetation and wetlands are high-scoring surface cover types, which often require large areas to be set aside within the site boundary.
• Intensive green roofs are often considered as part of densely developed sites with the potential for accessible roof terraces. Careful consideration should be given to building safety regulations and on-going maintenance and irrigation.
• Standard trees planted in connected tree pits encourages larger beds and understorey planting. The latter can be measured alongside the anticipated area of the tree canopy above.
• Extensive Green Roofs need to have a minimum substrate depth of 80mm.
• Flower-rich perennial planting provides varied seasonal interest that attracts wildlife and pollinators. However, it will require a careful maintenance regimes.
• Rain garden planting will have similar benefits and considerations as perennial planting but can also form part of the SuDS strategy.
• Hedges can mitigate against pollution and form habitat corridors, but will require regular clipping.
• Standard trees planted in pits less than two-thirds of the projected canopy area of the mature trees are particularly suitable for streets trees and roof terraces. Pits can have constrained soil volumes which can restrict tree growth.
• Green walls can provide large surface areas but they will need careful consideration to meet building safety regulations and often require an irrigation system.
• Ground-cover planting is low-maintenance and can include evergreens for year round interest.
• Amenity grassland has low habitat value but maintains a consistent year-round aesthetic and can be good for play.
• Water features provide minimal biodiversity benefits compared to wetlands.
• Permeable paving is preferable to sealed surfaces for ecological value.
• Sealed surfaces do not contribute to habitat or natural systems and can therefore significantly lower the overall UGF score.