21. Sustainability

21.1. Introduction

Sustainability is the avoidance of the depletion of natural resources to ensure that environmental conditions are preserved for future generations.

A sustainable built environment is made of healthy and comfortable places to live and work. Sustainability brings a huge range of benefits to building owners, at the same time improving the conditions around them and creating more cohesive neighbourhoods.

Small sites can be exemplars of sustainable development, with benefits including lower operating costs and improved long-term investment. People often think that sustainable projects must have certain kinds of products and technologies to be sustainable, but sustainable design is about good outcomes, not a checklist of products.

In the UK, 49% of all carbon emissions come from the building sector, a much higher proportion of carbon emissions than transport, agriculture or clothing. If we are to transition to a low-carbon economy then all new development should play its part.

The emerging Lewisham Plan outlines key requirements for sustainability in twelve sections under the heading of Sustainable Design and Infrastructure. This SPD explains those requirements in more detail, with a special section on energy use as well as links to further resources.

In this chapter we set out some key strategies to ensure that small sites development is sustainable. The appendix provides more detailed information including:

Further guidance around cost and best practices
A glossary of sustainable building terms and standards
Specific guidance on Lewisham’s sustainable design policies for small sites
Useful external resources.

21.2. Key sustainability issues

21.3. What do we mean by sustainability?

Sustainable development reduces the use of fossil fuels, conserves water, uses environmentally sound building materials, improves biodiversity and flood management and enhances the health and wellbeing of occupants with good ventilation, daylight and improved comfort.

A table showing that of Lewisham's greenhouse gas emissions, 51% is domestic, 26% is transport, 20% is business and 3% is other.
Figure 77: Diagram showing the sectors responsible for the Lewisham’s carbon emissions
A table showing that of the UK's greenhouse gas emissions, 27% is transport, 21% is energy, 17% is business, 15% is domestic, 10% is agriculture and 10% is other.
Figure 78: Diagram showing the sectors responsible carbon emissions across the UK

21.4. Sustainable development on small sites

Projects on small sites can achieve high levels of sustainability. With fewer people in the decision-making chain, good design can take the lead.

In addition, specific compliance requirements for projects under 500sqm – which includes a large proportion of development on small sites – are fairly simple, leaving owners more flexibility about how they set their own agenda whilst meeting the targets.

Improving biodiversity, flood management and provision for cyclists all benefits the surrounding neighbourhood. For owner-occupiers the return on investment is very strong, both in reduced energy and water bills, and in improved comfort and health. Developers also maximize asset value and minimize future risk.

At the same time, sustainable requirements can seem unduly difficult for small sites, so how to best to maximise the benefits, balance costs and comply with regulations?

The biggest hurdle may be cost, since budgets for small sites are usually limited. The good news is that there are ways to help manage and reduce potential costs, though the best overall approach is to take a longer-term strategy and consider total investment rather than focusing solely on build cost. In many cases there is a clear return on investment, with owner-occupants being better off financially in the long run, and even the medium-term.

For a project owner, it can be difficult to understand what to focus on. Good project planning is key, no matter how small the project, and this means understanding planning requirements from the outset.

It is especially challenging to navigate requirements in the current environment where regulations are changing and becoming much tougher. But this might bring advantages for smaller sites, since there is still some flexibility. Developers of small sites can choose how far to push their project in terms of energy use, material sustainability and so forth. Hopefully this SPD will show some key take-aways to focus on and make the journey that much more clear.

21.5. Sustainable construction misconceptions

Green building products are expensive, difficult to find and to build with
Green features can be added onto a project in later stages at no extra cost
Builders don’t understand green building and will price in extra risk
Build costs far outweigh operational costs so they should take precedence

21.6. Affordability

One of the biggest hurdles to sustainable investment is the perception of high up-front costs. As a developer looking at a small site, cost will be one of the most important factors in determining whether a project is viable.

21.7. Affordability tips

Relative costs are falling
The green building market is evolving quickly, offering more choice – with “normal” building products playing a part – and increasingly competitive pricing compared to conventional building methods. Contractors have better knowledge of sustainable construction and therefore reducing the price of risk. The benefits of real projects are now widely demonstrated, showing positive return on investment.

Capital costs vs. in-use costs and long-term costs
For small sites especially, up-front or capital costs aren’t the whole picture. There are plenty of sustainable strategies that are free or low-cost, or that increase costs in one place but reduce costs elsewhere.

Others add up-front costs but significantly lower operational costs, making a positive return on investment over time (especially in lowering energy bills). Furthermore, others – like investing in more robust materials, making buildings airtight and incorporating better site drainage – reduce future maintenance costs.

It is also worth considering that Building Regulations are becoming more demanding, and in only a few years some standard building practices, like gas heating, will be on their way to becoming obsolete. Buildings are meant to last, and designing sustainably is designing for the long term.

Focus on low-cost passive design to make the biggest energy savings
The cheapest ways to reduce energy use with the most co-benefits for the occupants involves simple, passive design: compact building form and layout, correct window sizing and placement, and building with sufficient insulation to keep occupants warm in winter and cool in summer, all of which improve personal comfort as well.

Aiming to achieve the same levels of energy use with solar photovoltaics (PV) is not only impossible in most cases, but also far more expensive to do and with no co-benefits. PV achieves the highest value when it is applied after other energy-saving reductions are already in place.

Key targets
Focusing investment on a few key areas with the biggest benefit for a project can ensure they are delivered in the final building.

For smaller sites, it can help to focus on a few key deliverables, for instance improving insulation and ventilation, and eliminating gas heating.

Sustainable strategy from the get-go
Make sure the architect or builder knows what your sustainability targets are, and make sure they collaborate with you to achieve your targets right from the start. There can be several ways to achieve energy savings, each with their own trade-offs. So discussing what you want to achieve right at the start when there is design flexibility will save build cost. It may help to hire an independent specialist to compare different strategies and find the “best value” way of doing things.

A photograph of a shiny contemporary house.
Figure 79: This new home in Sydenham Park Conservation Area is designed by Ian McChesney Architects using Passivhaus principles. The dark reflective surfaces mirror the surrounding trees and context, quietly absorbing it into its context (website: www.mcchesney.co.uk, photography: Adam Scott).

21.8. Steps in the Energy Pyramid

Figure 80 sets out a pyramid of hierarchy for sustainable design in small sites. The bottom steps of the pyramid have the lowest upfront cost (and are even sometimes cost free), whilst also having the largest impact on energy saving. The higher up in the pyramid, the more expensive and less impact the strategies have.

All projects should aim to use as many of the strategies in the first step as possible. For schemes to perform at a level of 35% less energy use than Building Regulations, the first three steps are needed, and to target a zero carbon development all steps are needed.

The strategies in the steps may vary depending on whether your project is new-build or a renovation:

Step 1 – Passive design

Step 2 – Low-carbon heating

Step 3 – Efficient electricity use

Step 4 – Renewables

Renovations and extensions
Step 1 – Passive design

Step 2 – Switch to low-carbon heating

Step 3 – Upgrade to efficient equipment

Step 4 – Renewables

A diagram showing the different ways of saving energy, with passive design as the most effective, and then efficient energy use, innovative solutions and offsetting energy use.
Figure 80: The Small Sites Energy Pyramid, demonstrating that the least expensive energy-saving methods are the most effective, and increasing capital investment often results in diminishing returns.

21.9. Policy requirements

Some policies have quite different requirements for small sites depending on whether they are classified as Minor (under 500sqm) or Major (under 2500sqm). The borough must support all sizes of project appropriately, and requirements for smaller projects are accordingly much simpler, requiring smaller project teams and quicker timelines.
The following tables describe some of these differing requirements. Further background and explanation to the policies outlined in the Sustainable Design and Infrastructure requirements of the Lewisham New Plan can be found in the appendix.

Sustainable Development and Infrastructure policies for Minor Developments
PolicyProject TypeRequirement
SD2Residential new-build onlyHQM Certification
SD4All developmentsBe able to connect in future to a HN
SD5All developmentsDescribe how heat risk is minimised
SD6In AQ focus areasAir Quality Assessment
SD7In flood zone 2-3Flood Risk Assessment
SD8All developments50% reduction in runoff, permeable surfaces
In critical areasMeet greenfield runoff rate, permeable surfaces
SD9Residential only105 litres per head per day + 5 litres external use
SD12All developmentsAdequate refuse storage
Sustainable Development and Infrastructure policies for Major Developments
PolicyProject TypeRequirement
SD2All major residential developmentsHQM Certification
All other major developmentsBREEAM Certification “Excellent” rating
SD3All major developmentsOn-site energy reduction of 35% of energy use (compared to Part L) plus minimise non-regulated emissions
All major developmentsIf zero carbon cannot be achieved on site, contribute to offset programme
SD4All developmentsDesigned for future connection to heat networks
SD5All developmentsDescribe how heat risk is minimised
SD6All major developmentsAir quality assessment
SD7All major developments in Flood Zone 1, 2, 3a, and 3bFlood risk assessment
SD8All major developmentsMeet greenfield runoff rate, permeable surfaces where possible
SD9All major developmentsNo deterioration of watercourse, meet local sewerage capacity
SD10All major residential developments105 litres per head per day + 5 litres external use
All major non-residential developmentsBREEAM Excellent achieved for the Water category
SD11New waste management projectsTo be prioritised
SD12All major developmentsCircular economy statement
All major developmentsAdequate refuse disposal