Case studies

EXECUTIVE SUMMARY

This document brings together examples of low energy concrete buildings from across Europe and presents them in an accessible format. It is hoped that the information provided will be of assistance to marketers and other interested parties within the cement and concrete sector. The case studies provided are particularly relevant to the building applications and climates throughout Europe.

Sustainability is an issue that continues to grow rapidly within the construction industry, influencing many of the activities and processes within the sector. Increasingly, it is the need to both slow the onset of climate change and also mitigate its effects, which are behind the rapid move towards improved sustainability in building design and operation. In practical terms, this has resulted in a much greater emphasis on enhancing the performance of the fabric and the lowering of CO emissions resulting from building occupation. The drive to cut emissions and reduce energy usage is reflected in tightening construction regulations and standards across Europe. Underlying many of these changes is the introduction of the Energy Performance of Buildings Directive, which came into force on the 4 January 2006.

The Energy Performance of Buildings Directive (EPBD)

The EPBD should greatly improve awareness of energy use in buildings, and is intended to promote increased investment in energy efficiency measures. The key objectives of the Directive are to improve energy performance by requiring:

a methodology to calculate the energy used by buildings;
minimum energy requirements for new buildings and large buildings undergoing renovation;
energy certification of buildings;
regular inspection of boilers and air conditioning systems.

Legislation must be in place by January 2006, and will affect all buildings, whether they are domestic or non-domestic. A key factor underlying the creation of the Directive is the fact that there are around 160 million buildings in the EU, which are responsible for over 40% of its energy use, and around 40% of its CO₂ emissions.

Low Energy Concrete Buildings

In meeting the challenges of the EPBD, the priority for architects and engineers is to make greater use of passive techniques to achieve a comfortable environment, which means working with the climate, building location and the properties of construction materials to minimise energy use. The Directive therefore represents a good opportunity for the cement and concrete sector to promote the energy efficiency and thermal performance benefits of high thermal mass concrete buildings.

The thermal mass provided by concrete makes it a particularly effective material for regulating the internal environment of buildings and minimising the use of heating and cooling energy. Thermal mass is essentially a measure of a material's ability to store and exchange heat with the environment. In practical terms this means that concrete buildings often have a relatively long warming up and cooling down period, which ensures a very steady internal temperature. Buildings with a low thermal mass are much more sensitive to changes in the internal and external temperature, resulting in the potential for a much greater variation in internal conditions. In low energy building design, the beneficial properties of thermal mass can be used in several ways to reduce energy use and provide good internal comfort:

In cold weather, it can be used to store passive solar gains during the day for night-time heating: Concrete floors and walls can absorb heat from the sun during the day, and then slowly release it at night as the temperature falls. This is called passive solar design, and can be used to significantly reduce heating energy requirements. The same principal also applies to heat from internal appliances such as lighting, cookers, and electrical equipment, which is also captured by the thermal mass.
Thermal mass can increase the efficiency of heating systems, enabling relatively small boilers to be used, operating at peak efficiency. The thermal stability of the building also prevents inefficient cycling of boilers, enabling them to switch off for long periods without a significant drop in internal temperature.
Thermal mass can help reduce the occurrence of overheating in the summer: Excess heat is absorbed during hot weather, helping stabilise the internal temperature. This heat is then purged at night by allowing the cool night air to ventilate the building. This technique can avoid or limit the need for energy intensive air conditioning.

Research carried out by CEMBUREAU shows that the benefits of solid buildings appear in all European climates, and the advantage with regard to annual energy consumption for a solid compared to a light-weight building varies between 2 and 20 percent depending on location/climate. However, even a modest reduction can have a significant impact in terms of improving the life cycle performance of a building, and lowering its environmental impact.

Case Study Buildings Included in this Guide

The case study buildings included in this document generally make use of one or more of the techniques outlined above as part of their overall low energy design. For simplicity, they have been grouped according to use i.e. office, residential, or other types of building.

The next section of this document contains a short summary for each case study, and also contains links to the full text. As might be expected, in many cases the information provided is in a broader context than simply low energy design which is of course only one of a number of design considerations. However, this is useful as it highlights the broader role that concrete can play in providing practical and sustainable buildings that fulfil a range of requirements including good durability, sound insulation and overall structural performance.

Inventory of Research Projects

Also included in this document is an inventory of research projects and programmes that focus on the use of thermal mass in building design across Europe. This provides background information on current areas of research within this field, and highlights some of the issues currently being examined.