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Environment and Energy


Version: July 2008



The University of Cambridge is committed to the concept of environmental sustainability. University Environmental Policy states that: “In achieving excellence in teaching and research, the University of Cambridge aims to manage its activities, buildings and estates to promote environmental sustainability, to conserve and enhance natural resources and to prevent environmental pollution to bring about a continual improvement in its environmental performance.”

The University has a strong track record in procuring high-quality, long-life buildings that are constructed efficiently and aims to ensure that its buildings are designed and constructed in accordance with best practice principles. It subscribes to the principles set out in the 1994 Latham Report (Constructing the Team) and the 1998 Egan Report (Rethinking Construction) for the delivery of exemplary sustainable buildings to manageable timescales and budgets.


2.1 Whole Life Costs

Good environmental practice usually goes hand in hand with good economic practice. Measures to reduce the consumption of energy and water not only benefit the environment by reducing emissions and conserving resources, but will also result in substantial financial cost savings over the lifetime of the building. The cost of energy and water are likely to rise significantly faster than RPI over the coming decades as resources become more scarce and environmental controls on utility companies increase. Cost savings that might seem marginal at today's prices could well increase considerably as these price rises come into effect throughout the life of the building.

It has been estimated that for educational buildings the Design : Construction : Running Costs are in the ratio 0.1 : 1 : 2-3 (salary costs un-assessed). Combining economic and environmental assessment tools to obtain "best value" solutions in both financial and environmental terms has the potential to make a significant contribution to achieving sustainable development. (Other estimates put the running cost ratio even higher).

Financial assessments of any project should therefore consider the building's Whole Life Costs, including its design, construction, running and eventual deconstruction, rather than focussing purely on initial design and construction costs.

2.2 Integrated Passive Design

The redeposit draft of the Cambridge Local Plan requires that all new developments will be required to minimise energy consumption and maximise energy efficiency. This should be achieved through the sustainable design of buildings including their location, grouping, orientation and layout, making use of passive solar heating and natural daylight and ventilation. Also, by using sustainable building materials and construction techniques. Detailed guidance for Planners and Developers about the Council's requirements is provided in the Cambridge City Council Sustainable Development Guidelines.

Design teams should ensure that integrated passive design features are built into the design of new buildings from the earliest stages of the design process to maximise the possibilities for reducing environmental impact and running costs of the building over its lifetime. They should be able to demonstrate a proven track record in the successful design and construction of buildings using integrated passive design principles.

The main elements of integrated passive design are:

  • Orientation: making best use of high summer sun angles and low winter sun angles on southern exposures while minimising excessive solar gain on east and specifically west exposures from low year-round sun angles.
  • Glazing: sizing, positioning and detailing windows to get the most benefit from the sun while avoiding overheating in summer and heat loss in winter.
  • Thermal Mass: providing sufficiently exposed thermal mass to store heat from the sun in the winter and act as a heat sink for cooling in the summer. The benefits of thermal mass are often lost through excessive wall, ceiling and floor coverings.
  • Insulation: specifying high levels of insulation to reduce unwanted heat loss or heat gains through the roof, walls, doors, windows and floors.
  • Natural Ventilation: designing clear and robustly controlled air flows through buildings for daytime and night time cooling. Building air-tightness forms a critical component for achieving effective natural ventilation.
  • Zoning: providing thoughtful zoning to allow different thermal requirements to be compartmentalised. Substantial savings can be achieved.

Exemplary sustainable buildings do not have to cost more, provided that good passive design features are fully integrated into the design process from the earliest stages rather than tacking on expensive overtly environmental features to fix problems that could have been designed out in the first place.

Good passive design buildings are generally well liked by their occupants and provide healthy and pleasant environments to work in. However, occupants should be provided with some form of simple direct control over their local environmental conditions to make them more accepting of the wider temperature ranges over the course of a year than would be found with air-conditioned buildings.

Fully integrated passive design features are fundamental to the building's efficient operation and must not therefore be discarded or compromised in any subsequent value-engineering exercises.

Further detailed guidance on aspects of integrated passive design that should be considered by design teams can be found in Annex B.


3.1 BREEAM Assessment

A BREEAM (Building Research Establishment Environmental Assessment Model) assessment should be carried out on all new buildings of over 1000 m² with a target to achieve a rating of 'Excellent' with a minimum rating of 'Very Good' in cases where there are good and explicit reasons why an excellent rating could not be achieved. Similarly, an EcoHomes assessment should be carried out on any residential development of over 10 dwellings with a target to achieve a rating of 'Excellent' with a minimum rating of 'Very Good' in cases where there are good and explicit reasons why an excellent rating could not be achieved.

Many of the credits awarded under the BREEAM and EcoHomes systems will already be available as a result of the University environmental policies and existing travel patterns. It is therefore important that in carrying out the assessment, particular emphasis is focussed on achieving high scores relating to CO2 emission targets to ensure that the building performs well from the point of view of energy efficiency and its contribution to global warming.

The BREEAM assessment should be of a 'Bespoke' type and should be implemented from the very start of the project process to enable it to inform the design of the building.

BREEAM and EcoHomes are the recognised standards in the UK for assessing the environmental sustainability of buildings and houses. The University is currently in discussion with HEEPI (Higher Education Environmental Performance Initiative) to develop a Higher Education framework to increase the applicability of buildings in the sector. There may also be a modified form of BREEAM due to its inclusion as a key component of the Government's Code for Sustainable Buildings, which is expected to be introduced in 2005.

3.2 Part L Building Regulations

In order to meet the requirements of the EU’s Energy Performance of Buildings Directive, the UK government revised the Building Regulations 2000. These changes came into effect April 2006 and apply to both construction of new buildings and renovation of existing buildings with a total surface area of over 1000m 2. The government estimates that the improved energy efficiency measures will save up to one million tonnes of carbon per year by 2010. For example, Part L aims to reduce carbon emissions by 25% from 2002 standards in new buildings, equating to a new reduction of 40% from pre-2002 levels. Distinguishing the Part L revisions from previous Parts is the fact that although Part L establishes target, the revisions are not prescriptive. Instead, they allow building designers an element of flexibility in how they achieve the target emissions rate.

The Building Regulations divides Part L two major sections: domestic and non-domestic. L1A and L1B cover domestic dwellings and parts L2A and L2B deal with the non-domestic counterparts. Given the composition and size of its estate, Parts L2A and L2B are of greatest interest to the University.

3.2.1 New Buildings

Part L2A covers the energy efficiency regulations set forth for new, non-domestic buildings. In the 2006 revisions, it performs the following:

  • Caps carbon emissions allowed to be designed into the building
  • Imposes minimum construction quality criteria

CO2 target

The revisions to Part L set maximum carbon dioxide emissions for whole buildings. The target emission rate (TER) is measured in kgCO 2/m 2/year. The predicted emissions from the actual building design are known as the building emission rate (BER) and may not exceed the TER.

Quality of Construction & Commissioning

The minimum construction quality criteria imposed includes the following:

  • The builder should have an appropriate system of site inspection in place to give confidence in the construction process.
  • Upon completion, the building will be subject to two tests: air permeability and pressure testing; and commissioning of the building services systems.

3.2.2 Insulation / thermal bridging

University buildings should be well insulated, not only from heat loss but also from heat gain. According to the building regulations 2006, “building fabric should be constructed so that there are no reasonable avoidable thermal bridges in the insulation layers cause by gaps within the various elements, at the joints between elements and at the edges of elements,”(L2A, pg 22). Insulation should be provided to achieve at least the U-values as shown in Table 4 below. Details at junctions should be designed to minimise the effects of thermal bridging.

Table 4: Limiting U-Value Standards (W/m2K)

Element (a) Area-weighted Average Value (b) For any individual element
Wall 0.35 0.70
Floor 0.25 0.70
Roof 0.25 0.35
Windows1, Roof Lights/ Windows2 & Curtain Walling 2.2 3.3
Pedestrian Doors 2.2 3.0
Vehicle Access & Similar Large Doors 1.5 4.0
High Useage Entrance Doors 6.0 6.0
Roof Ventilators (incl. smoke vents) 6.0 6.0

1Excluding display windows and similar glazing. There is no limit of design flexibility for these exclusions but their impact on CO2 emissions must be taken into account in calculations.

2The U-values for roof lights and roof windows in this table are based on the U-values having been assessed with the roof lights or windows in the vertical position.

In addition, Part L2A recommends that builders have an appropriate system of site inspection in place in order to give confidence that the construction procedures actually achieve the require standards of consistency.

3.2.3 Air Permeability

The exfiltration of warm air can account for as much as 30% of the heat loss through a building's envelope. As insulation standards improve, heat losses and gains as a result of air exfiltration and infiltration will become more significant. Achieving good air tightness performance is also a good indicator of good construction practice.

Air leakage tests should be carried out on any new building with a floor area greater than 500 m² in accordance with the guidance provided by CIBSE TM 23 to show that the air permeability of the building does not exceed 10 m³/h/m² at a differential pressure of 50Pa. This is the “reasonable limit for design air permeability” as recommended by Part L2A.

3.2.4 Energy Performance of Buildings Directive

Part L2B applies to refurbishments and renovations in non-domestic buildings with over 1000m2 of useful floor area. It provides:

  • Definition of ‘consequential improvement’, the type of work expected/permitted, and criteria for the improvement’s feasibility
  • Guidance on efficiency measures that should be brought to bear when large extensions, small extensions, conservatories are added, when there is a material change of use or alteration or when controlled or fixed services (lighting, heating, cooling, and ventilation) are upgraded or expanded.
  • Guidance on dealing with ‘thermal elements’ (walls, roofs, and floors) and taking reasonable steps to limit heat gains and losses.

Consequential Improvement

In a building over 1000m 2 where the proposed work consists of an extension, the initial provision of any fixed building services, and/or an increase to the installed capacity of any fixed building service, the revisions require the whole building to comply with Part L if this ‘consequential improvement’ is technically, functionally, and economically feasible.

Thermal Elements

According to the 2006 revisions, floors, roofs, and walls must meet differing specified U-values in the event of ‘Provision’ (when an element is new or replaced), ‘Renovation’ (when more than 25% of an element is being renovated), and ‘Retention’ (when an element is retained as part of a material change of use or becomes part of the thermal envelope). Renovation requires the whole building to meet the specified U-value. With retention, the whole building must be upgraded provided it can be done within a 15 year simple payback.

Building Work Guidance

Additional building work guidance outlined in the 2006 Part L revisions include:

  • Part L regards large extensions as new buildings. Thus, they must follow L2A in addition to the ‘consequential improvements’ to the remainder of the building. (large extensions = greater than 25% of the total useful floor area of the existing building)
  • Heating, hot water, lighting, and cooling and air handling plants must meet minimum efficiency criteria and be correctly commissioned. The minimum efficiency may not be less than that of the system being replaced. Where a new fuel type is being used the efficiency should be adjusted by the relevant CO2 emission factor.
  • New building systems must have separate controls for each ‘zone’ corresponding to solar exposure, occupancy period, or type of use. Central plant serving the zone-based systems should have a default setting of ‘off’. Heating and cooling may not be permitted to operate simultaneously.
  • Energy meters should be installed to assign at least 90% of energy consumption to its end use category.
  • Fittings, including windows, roof lights, doors, and vents must be draught proofed to specified standards.

3.2.5 Building Services

The 2006 revisions requires controls for heating, ventilation, and air conditioning subdivided into building ‘zones’ with default setting as ‘off’. Furthermore, they expect energy meters to enable at least 90% of energy consumption for each fuel to be assigned to its end use category. In fact, the revisions required automatic meter readings and data collection facilities for buildings over 1000m 2. They also provide additional requirements for the performance and efficiency of heating and hot water, cooling, air handling plant and pipe and duct insulation, as well as lighting standards and controls.

3.3 Climate Change

Design teams should demonstrate clearly how the building will cope (or be adapted to cope) in so far as it is practicable with the effects of climate change.

Under the UKCIP 'medium-high emission scenario' average UK temperature will rise by up to 3.5°C by 2080, by which time, temperatures in London will be similar to those currently experienced in Marseilles. Building designs should be based on UKCIP 'medium-high emission scenario' projections rather than on historical climatic data. It is especially important to consider overall temperature ranges as well as peak temperatures where night-time cooling is an integral part of the cooling strategy.

Recent studies by Arup suggest that mixed-mode ventilation stems incorporating both passive and mechanical ventilation, coupled with high thermal mass with exposed surfaces and extensive solar shading are likely to be best able to cope with the effects of climate change.

The design of drainage systems and below-ground works should take into account the possibility of increased maximum run-off rates, increased risk of flooding and rising groundwater levels.

3.4 Materials

Locally sourced and/or reclaimed material should be used wherever possible.

Major building elements (i.e. upper floor slab, external walls, roof and windows) should achieve an overall 'A' rating as detailed in the Green Guide to Specification 'A' (BRE 1998).

Timber, including structural timber, cladding, carcassing, internal joinery and panel products should usually be FSC (Forestry Stewardship Council) certified unless there are other overriding considerations for using alternative sources of timber.

In the choice of materials consideration should be given to the embodied energy of any given material.

Insulants should not contain, or require during manufacture, ozone-depleting substances.

Paints and other wall coverings should be low or free of volatile organic compounds (VOCs).

Substances containing CFCs (chlorofluorocarbons) and HCFCs (hydrofluorocarbons) should be avoided.

Fire suppression systems should not contain halons or penta/octa/deca-BDE (bromodiphenyl ether) flame-retardants.

3.5 Drainage

All laboratory wastewater systems should be segregated from domestic wastewater systems to permit the sampling of effluent by the Regulatory Agencies to assess Trade Effluent Consent conditions to comply with the requirements of the Water Industry Act, 1991. Sampling facilities should be provided at the exit point of laboratory waste water systems to permit the taking of samples of effluent by the regulatory authorities.

External drainage systems should be based on SUDS (Sustainable Urban Drainage Systems) requirements to help manage run-off that might otherwise cause flooding and also help to preserve water resources.

3.6 Ecology / Conservation

Developments of greater than 1,000 m² floor space or housing developments of more than 10 houses will require the completion of a biodiversity checklist, in accordance with the requirements of the Cambridgeshire County Council Biodiversity Action Plan. This must give details of how the development will seek to protect existing habitats and species, and give details of mitigation, enhancement or compensation strategies.

3.7 Transport

Showers and changing rooms should be provided for buildings with a projected population of 50 or more employees.

Drying rooms with lockers for hanging wet clothes and for keeping a change of clothes should be provided in all new buildings.

Sufficient secure covered 'Sheffield' cycle racks should be provided close to the building entrance to comply with Cambridge Local Plan requirements.

3.8 Recycling and waste management

Adequate facilities should be provided for the storage and collection of segregated recyclable wastes (e.g. paper, cardboard, glass and aluminium cans).

For scientific and technical sites additional consideration must be given to the provision of adequate facilities for the storage and collection of other wastes (e.g. chemical, clinical, radioactive and other hazardous wastes such as waste oils).

3.9 Construction Waste

Contractors should develop a construction waste minimisation plan. Key waste streams should be identified at the start of the project and measures implemented to reduce these wastes. Clear and accessible space for waste segregation and good storage facilities for raw materials to minimise damage should be provided during construction works.

Targets should be set with the aim of minimising waste production on each project. Waste streams arising during construction should be measured and compared with established benchmarks (e.g. the BRE SMARTWaste web-based tool).

For more information see the other guidance on Buildings provided by the Environmental Office:

3.10 Post completion

On completion, new buildings should be subject to POE (Post Occupancy Evaluation).


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