At NBS, one of the requests we receive on a regular basis is for advice on how to specify sustainability or, sometimes, how to write it into a contract. Before we tackle this, however, let’s address a more fundamental question: ‘Is it actually possible?’

If we accept that sustainability is a performance requirement, then the short answer is ‘yes’, but as you might expect, it is not as simple as calling up a single clause or contract condition.

Defining ‘sustainable’

It has become quite fashionable in recent years for construction clients, consultants and contractors to declare how ‘green’ they are, but we talk about ‘green’ in the context of the built environment the concept is even more diverse. Usually the focus turns to the use of natural resources or waste minimisation, but that’s not the whole story. For some, it’s associated with the UN Conference on Environment and Development (UNCED) held in Rio de Janeiro, Brazil, in 1992. Others associate it with Our Common Future externallink from the United Nations World Commission on Environment and Development (WCED) – also known as the Brundtland Report after the former Norwegian Environment Minister and Chair of the Commission.

Bruntland’s report includes what has since been widely adopted as the definition of sustainable development, i.e. that which can:

“Ensure that it meets the needs of the present without compromising the ability of future generations to meet their own needs.”

So, how is this achieved in practice?

Sustainable construction

In order to specify compliance with a performance requirement, we must first define what that requirement is, and then set out the criteria which will be used to measure and enforce conformity. Unfortunately, as we’ve noted, there are a lot of definitions; and therefore a lot of possible criteria.

If you were asked for a design that ‘complied with the Building Regulations’, you would immediately realise that there are a huge number of possible solutions. And so it is with sustainability, except that the range of solutions is much broader. For example, there is also a social dimension to sustainability, with the focus being on the needs of communities and individuals, and their relationship with the building itself.

Design and specification

Designers need to research and select products which meet certain performance criteria – perhaps those which have certain properties, or contain materials which can be assessed against published standards for embodied carbon or some other chemical constituent. The building itself is a sum of these parts, and combined they contribute to its overall performance in areas such as airtightness or durability.

It should be recognised that the majority of a building’s carbon emissions result from use rather than construction – things like heating and cooling, cleaning, maintenance and so on. To some extent these are influenced by the products used in construction, but they are also a function of the design – height, alignment, space enclosure, shape, location, and even human preference and behaviour.


One of the stated aims of the UK development control regime is to improve sustainability. This is addressed in a variety of ways, including Building Acts and Regulations which prescribe minimum standards for things like durability, acoustic or thermal performance and waste minimisation, or the prevention of use of ‘deleterious materials’ – those which may be harmful to the environment.

Specific legislation exists concerning health and safety in construction, such as the CDM Regulations, or those to do with lifting, working at height or in confined spaces, or with substances hazardous to health. These have a direct bearing on the sustainability of a project if human wellbeing is one of the assessment conditions.

Finally, pieces of legislation such as the Localism Act 2011 place power in the hands of local communities with regard to transport, planning and infrastructure.

Business case

A major obstacle to the sustainability agenda is the belief that sustainable buildings are more expensive. Some research has suggested that the cost of constructing a green building may be as much as 17% higher than the cost of building a conventional structure. However, research is emerging which suggests that there is a premium to be received by tenants of so called ‘green’ buildings – arising from businesses that see the advantages of enhancing their sustainable credentials as part of the Corporate Social Responsibility agenda.


When looking at a compliance model for sustainability, there is plenty of assistance out there. Assessment models such as BREEAM, LEED, CEEQual, Greenstar and others provide a series of matrices which allow targets to be set and compliance measured. It is important to note that these are not simply concerned with construction, meaning that location, land use, post-occupancy efficacy and user satisfaction may also be taken into account.

Building Information Modelling (BIM)  is potentially a vital tool in this process. BIM is concerned with information, and information which supports sustainable credentials can easily fall into this category, whether it relates to embodied carbon or risk analysis for health and safety.


Sustainability comes in many flavours, and it sometimes needs to be taken with a pinch of salt. Anyone who has boarded a plane in the UK recently will be fascinated to note that they all now seem to carry energy labels similar to those displayed on fridges and dishwashers. This is an EU requirement, but it is remarkable how highly some of them score when we consider the understood negative effects of burning jet propulsion fuel. The reason being is that they are compared with an industry benchmark rather than an independently assessed, challenging target.

In a similar way, a construction project can be designed to align with a particular version of sustainability. The challenge here is not just to make the design compliant, but to find the version that truly delivers the results we are all looking for.