Energy consumption in buildings currently accounts for over 40% of all energy consumed in Europe. This is by far the greatest share of total energy consumption, ahead of transport and industrial production. Approximately 85% of the energy consumed in buildings is attributed to heating and hot water generation, which means that the potential for energy savings is huge: according to the EU Commission, the energy efficiency of European building stock can be increased by 50%. Improvements can be made not only to heating systems and other technologies, but also in the area of insulation. Higher targets for energy savings and reduced CO2 emissions can be achieved by combining perfectly co-ordinated components to create efficient, fully integrated systems.

Of particular note is the potential for making heating systems (for room and water heating), air conditioning and lighting more energy efficient using the following technologies, in order to attain the energy standards of low-energy houses and passive houses:

  • oil and gas heating (for example, condensing boiler technology)
  • heat distribution (for example, pumps), heat emission (for example, radiators and underfloor heating systems) and controls (for example, valves)
  • ventilation technology (for example, ventilation devices with heat recovery)
  • air-conditioning technology
  • combined heat and power generation
  • heat insulation (energy-efficient products and components)
  • lighting technology (for example, daylight redirection systems)

Another option is to replace conventional fossil fuels, such as oil or gas, or combine them with renewable energy sources. Finally, renewable energy resources are available in almost unlimited quantities and provide options for long-term, sustainable energy as they reduce our dependence on fuels that have a limited supply. Renewable energy sources also make a valuable contribution to environmental protection and climate control because they significantly reduce CO2 emissions.

The key application areas for renewable energies in buildings are as follows:

  • solar thermal technology for domestic hot water and/or to support heating systems
  • photovoltaic technology to generate electricity for domestic use or for grid supply
  • innovative wood-burning solutions, for example, using split logs, wood pellets or wood chips
  • solutions that leverage environmental heat or near-surface geothermal heat, for example, using heat pumps for heating

Germany has an established tradition of energy saving that stretches back at least as far as the oil crises of the 1970s. Since then, German regulations have been placing increasingly stringent demands on heating insulation and heating systems. The German Energy Saving Ordinance (EnEV) has been in force since 2002 and was amended in 2007. The EnEV envisages a holistic view of the building envelope, systems engineering and the preparation and conversion losses of the fuels used. A further planned amendment of the EnEV aims to tighten the rules on energy consumption in buildings by 30% before 2009.

For several years, the Federal government's energy saving regulations for buildings have been accompanied by its concerted promotion of the research and development of innovative technologies for the "buildings of the future", which allow standards to be raised.

State sponsorship (for example, through financing with KfW Förderbank) is directed in particular at energy-efficient and environmentally friendly applications that are not yet economically viable. For many years, German industry has been adapting to these challenging conditions and availing of the opportunities for sponsorship, and now offers particularly efficient technologies. For example, the German heating industry achieved fresh export success last year thanks to a growth of over 100% in the market in some European countries. It currently enjoys a market share of 60% in the EU and 33% worldwide. Germany holds a 90% share of the global renewable energy market. Even in the highly competitive photovoltaics market, Germany is the clear front-runner with a share of 50%, surpassing even Japan.


Picture: BDH

Condensing Boiler Technology

In Europe, the main technologies used for room heating and the heating of drinking water are hydraulic heating systems with oil and gas central-heating boilers. Since the largest portion of energy is consumed by the generation of heat in buildings, the renovation of heating systems is one of the areas offering the greatest potential for savings. The German heating industry is at the forefront of efficient high-tech boiler development.

Low-temperature boilers, where the temperature of the water in the boiler is adjusted in line with the external temperature, set the standard for many years. Even with these boilers, the flue gas loss and standby loss were only between 10% and 12% of the effective heat energy.

The latest-generation boilers are called condensing boilers. These represent an enhancement of the low-temperature boiler and reduce heat loss considerably. As a result, the amount of heat now released from the fuel is almost at the limit of what is physically possible. Condensing technology also utilises the condensation heat contained in the flue gas, which would otherwise remain unused. An additional increase in efficiency is achieved through lower flue gas temperatures, which mean that less flue gas is lost. As a result, condensing boilers can achieve efficiency values in excess of 98%.



Condensing boilers are cost-effective because the cost of purchase is recovered in terms of energy saved within just a few years. Replacing an outdated heating system, for example, with an oil condensing system in a single-family or two-family house in Germany costs, on average, ¤8,000. At a heating oil price of 60 cents per litre, a current annual heating oil consumption of, say, 4,500 litres (for heating and hot water) and a reduction in consumption of 30%, approximately ¤1,350 can be shaved off the annual oil bill. This means that the cost of the condensing boiler system would be redeemed over approximately 6 years.


Picture: BDH


Since renovation projects often take a long time to complete, older builds often do not meet the latest insulation standards and use disproportionately large amounts of heat energy for room heating. However, with a professional energy-saving renovation, any building can be as well insulated as a new build.


Picture: dena

Inappropriate insulating measures, on the other hand, may cause structural damage. Expert consultation and planning is therefore just as important as successful project execution by an experienced company and the use of suitable building materials.

Picture: Solarpraxis

Thanks to Germany's long tradition of energy saving in residential, commercial and industrial construction, German engineers and building contractors can be counted on as reliable partners for projects both at home and abroad. German partners are involved in many such projects all over the globe at all levels, from consulting to planning and execution.

Potential savings
German building stock currently consumes approximately three to (in the worse cases) ten times as much energy for heating as new builds. Up to 80% of the heat energy consumed for room heating can be saved by having insulation installed by a professional contractor and through energy-efficient renovation. Energy-efficient renovation of older builds has the added benefit of increasing thermal comfort at lower room temperatures.

Insulating techniques
Conventional building materials tend to be very good heat conductors. In other words, they do little to stop heat loss through the transfer of heat from inside the building to the exterior. Technology cannot eliminate this natural flow of heat but insulation can reduce it significantly.

To increase the insulating effect of a wall construction, additional insulating layers with low heat conductivity are added to older buildings. These insulating layers are usually positioned on the "cold" side of the existing structure. In the case of external walls, this is the exterior of the building.

In this case, the insulating materials must either be naturally weatherproof or fitted with weatherproof protection.

The following are all commonly used insulating materials and some also serve as thermal insulation composite systems:

  • Foamed plastic (polystyrene, polyurethane etc.)
  • Mineral wool, glass wool, cellular glass
  • Mineral materials, such as porous concrete, pumice stone, perlite
  • Injected cavity fill made of cellulose flakes, hemp-clay mixes
  • Wood fibre, wood shavings, cork
  • Plant or animal fibres, such as hemp, flax, coconut, wool
  • Reed plates
  • Calcium silicate plates (for example, for internal insulation)


Picture: Solarpraxis

Innovative insulation systems are also possible, for example:

  • Vacuum insulation
  • Transparent heat insulation

It is generally recommended that the following parts of a building be insulated:

  • Roof or top floor ceiling
  • Exterior walls
  • Basement ceiling, basement exterior (where relevant)
  • Glazed surfaces
  • Heating system and heat storage unit

Special regulations in Germany
The energy performance certificate introduced in Germany assesses the energy efficiency of buildings (for example, new builds and old builds that are to be rented, let or sold). Based on this rating, specific renovation measures are proposed to improve the energy efficiency of existing buildings.

The energy performance certificate is an inexpensive way for owners to obtain initial information about how to renovate their buildings. It records the most important details of the building, provides information about its current level of energy efficiency and indicates whether renovation would make sense in each case. Specific recommendations for renovation in the energy performance certificate provide a starting point for renovation planning or for a further, detailed energy consultation. In Germany, expert initial consultations are provided by, among others, energy consultants, planning offices and skilled craft companies. For many years, the Federal Ministry of Economics and Technology (BMWi) has also been promoting qualified, unaffiliated energy consulting, and has therefore played a role in the establishment of Germany's nationwide network of independent energy consultants.


Picture: dena

For potential buyers and tenants, the energy performance certificate provides a welcome point of comparison and a decision-making tool for selecting a building or apartment based on projected energy costs. Minimum energy-efficient standards must be met when performing extensive building renovations in Germany. These standards and those for new builds are regulated by the Energy Saving Ordinance (EnEV). Over the years, German regulations governing standards for energy efficiency have become increasingly rigorous and this trend will continue for the foreseeable future. The EnEV ensures that the insulation and technologies used in new builds meet high standards and specifies prerequisites for renovation based on the latest technological developments, while simultaneously taking account of economic viability.

As a result of the provisions enshrined in the legislation and the high demand for renovations, which can only be met by degrees, a large percentage of the labour force employed in skilled crafts or in the planning/consulting sector is currently involved in energy-efficient renovations.

German specialists are also employed as consultants or skilled craft providers on a global scale. The Federal Ministry of Transport, Building and Urban Affairs (BMVBS) and its partners foster a well-structured, high-quality transfer of knowledge as part of these projects. The BMBVS and the German Energy Agency (dena) support energy-efficient construction and renovation through well directed international projects, for example, in China. Specific measures include the publication of reference books, the hosting of regional seminars and conferences, representation at trade fairs and exhibitions, and the promotion of products and services from German companies.

The close collaboration between Germany and its international partners under the auspices of the International Energy Agency (IEA), for example, in the context of the "Implementing Agreement on Energy Conservation in Buildings and Community Systems" (ECBCS), affords German science and industry greater opportunity for teamwork on a global scale.

Combined Heat and Power Generation

In conventional power plants, only one third of the energy consumed is fully utilised. Combined heat and power (CHP) generators provide a viable, environmentally friendly alternative. CHP plants work on the principle of combined heat and power generation, whereby the energy consumed is simultaneously transformed into both electricity and useful heat.  As a result, up to 40% of the primary energy can be saved compared with centralised power generation and decentralised heat generation.

In addition to medium-sized and large CHP units, German companies also offer "mini CHP systems" with a capacity of up to 30 kW. Mini CHP units essentially comprise a combustion engine, a power generator and a system of heat exchangers.

The electricity generated in the generator can either be used in the building directly or fed into the public grid. The waste heat generated by the combustion engine is recovered by heat exchangers and can be used for heating purposes. The heat is usually stored in a buffer storage unit until needed.

The size of a small CHP depends on its capacity but is not generally larger than a standard boiler. The engines also make very little noise and therefore can easily be installed in basements. The capacity of a mini CHP unit can provide enough thermal heat for a large single-family house or multiple family dwelling. The greater the heating load required, the greater the amount of electricity generated and the sooner the cost of the CHP system will be recovered.

Small CHP units can be used in residential buildings, in recreational buildings (including hotels, guesthouses and restaurants), public buildings or healthcare facilities (including hospitals, care homes and health centres), in other words, wherever heating is required on an ongoing basis. In addition, standalone mini CHP systems without a connection to the grid provide an attractive alternative to traditional power generators in isolated areas.

German legislators recognized the environmental benefits of CHP systems many years ago and implemented appropriate measures such as the Heat-Power Cogeneration Act (KWK) and the Energy Saving Ordinance (EnEV) to promote and extend the use of combined heat and power generation. Electricity tax is not applied to the consumption of electricity generated by CHP, while the fuel used to generate the electricity is exempt from energy tax.

Germany currently has some 2,500 CHP units with capacities of between 50 kWel and 2 mWel. Since 1990, the electrical power of CHP engines has increased in Germany from 500 mW to more than 4,100 mW, which represents 3.5% of the national energy supply. Experts predict a further increase to 10%. In other words, a large number of manufacturers and a wealth of expertise have been present in Germany for several years. German manufacturers are continually pushing the boundaries of their technological innovations to make them even more effective and to identify new applications. These include, for example, the use of micro gas turbines to drive mini CHP systems.


Picture: Solarpraxis

Low-Energy Houses and Passive Houses

Particularly energy-efficient buildings offer economic benefits in the face of rising energy prices, help combat climate change and provide a very pleasant room temperature.

In Germany, buildings that meet the low-energy house standard have an annual energy requirement of between 30 and 70 kilowatt hours per square metre. The term "passive house", meanwhile, refers to particularly efficient buildings that do not require an active heating system to achieve a comfortable room temperature. To meet this standard, the annual energy requirement per square metre for room heating must be reduced to less than 15 kilowatt hours, while the building must also be equipped with ultra-efficient ventilation and heat recovery systems.

To achieve these values, renovation of the building envelope and the heating and ventilation systems must be planned and executed by professional experts. Energy-efficient optimisation of the building envelope includes doors and windows, as well as insulation of the exterior walls and basement, roof, roofspace and floor slab. Thermal bridges, in particular around windows and in entrance areas, are to be avoided as far as possible. Savings can be made in the building's HVACR (heating, ventilation, air conditioning and refrigeration) through efficient heat generation and distribution, a large proportion of passive solar energy utilisation and sophisticated ventilation technology.


Picture: Solarpraxis

Due to the multitude of energy-efficient buildings that have already been constructed in Germany (including passive houses), German companies have had the opportunity to acquire extensive expertise in meeting specific challenges in relation to building construction and technology. Changes in consumer behaviour play a key role in this context because the active ventilation systems required (in passive houses in particular) render many old and particularly inefficient practices superfluous, for example, tilting windows to ventilate a room.


Picture: Solarpraxis

Knowledge gained from and technologies used in the construction of energy-efficient buildings (for example, passive new builds) can also be applied to the renovation of building stock, including the optimisation of heating technology to ensure low wastage, ventilation measures and the avoidance of thermal bridges. German companies can achieve savings of more than 80% in a typical old build.

The "Energy-Optimised Construction" (EnOB) programme of the Federal Ministry of Economics and Technology and the "Low Energy Standards for Existing Buildings" project of the German Energy Agency (dena) provide impressive demonstrations of how, through best practices in energy-efficient renovation, existing buildings can meet the same standards as a low-energy house (see


Picture: BDH

Heat Distribution and Emission

Reliable and efficient heating of a building requires heat generation and distribution and a tailored heat supply to heat consumers.

A building's heat distribution system, which comprises pipework, pumps and line fittings, transports heat from the heat generator to the heat transfer point.

The heat transfer system, meanwhile, comprises radiators or heating panels and room temperature controls. A comfortable room temperature is easily achieved using the heat radiated by the system.

Picture: BDH

If the individual components work together efficiently, energy and costs are saved while comfort levels are increased.

Some key considerations in relation to efficient heat distribution and transfer are outlined below:

  • The latest energy-saving heat circulation pumps require less than half of the electrical energy required by conventional, unregulated pumps. Electronically commutated (EC) motor pumps are much more effective than the asynchronous motors used in the past, even when working with partial loads. Since EC motors use permanent magnets and therefore require little or no magnetising current, energy losses are very small.
  • Regulated pumps also eliminate bothersome noises in the heating system.
  • Configurable thermostatic valves enable precise room temperature regulation.
  • Time-controlled and temperature-controlled valves automatically ensure a comfortable level of room heating.
  • Perfectly proportioned and hydraulically balanced heating surfaces increase comfort levels and save energy.

Individual renovation steps in the area of heat distribution and transfer, such as hydraulic balancing, the installation of configurable thermostatic values or the replacement of obsolete thermostatic heads, produce the greatest energy savings per investment cost.


Picture: BDH

With modern, large-area radiators, comfort levels are increased, while the temperature of the working medium in the heating system may be dramatically reduced (low-temperature heating). Lowering the room temperature also produces significant energy savings. For example, lowering the temperature by 2°C using correctly proportioned and regulated radiators reduces heating costs by up to 12%.

The German government promotes efficient heat distribution and transfer through its programme of incentives, including direct subsidies for particularly efficient circulatory pumps.


A large proportion of electricity consumption in buildings is accounted for by artificial lighting. This is directly reflected in the running costs of many buildings. In the housing sector, at least 10% of electricity is consumed by lighting. In the office and commercial sector, lighting can even account for up to 50%. The bulk of this consumption is still based on economically and environmentally inefficient technologies like the traditional light bulb.

Light is still generated primarily by electricity passing through a light bulb, the oldest and least efficient technology. At most, just five percent of the electricity flowing through is converted into light. The unused remainder is transmitted into the environment as heat. Energy saving lamps are an alternative. Although they have been on the market since the 1980s, they are only gradually becoming widely used. At the same time, the previous concerns about light quality and warm-up periods are no longer valid. Such lamps are now on sale in the various designs of traditional bulbs and some are even dimmable.

The commercial sector still tends to use obsolete lighting systems. They generally consist of traditional fluorescent tubes, many of which have poor reflectors (or none at all) and inefficient ballasts. The light generated is absorbed within the tube itself and emitted into the room without direction. Simple retrofitting of reflectors can minimise the energy loss. Furthermore, modern ballasts can cut power consumption even further.

More than 2 billion light bulbs are sold every year in Europe. One can calculate that a shift to energy saving lamps would save 7.5 billion kWh and 4.5 million tonnes of CO2 in Germany alone. Assuming an electricity price of 20 cents per kilowatt-hour, this would imply savings of ¤1.5 billion for the residential sector as a whole.

The potential amount of energy to be saved in terms of lighting is enormous. Various measures can dramatically reduce the energy consumption both when planning and when modernising a building:

  • optimised use of daylight when planning a building (shade, electronic light intensity control, etc.)
  • use of highly efficient illumination
  • modernisation using energy-efficient lighting systems
  • use of intelligent lighting control

Over the last 15 years, the German lighting industry has developed new technologies which are three times as efficient as older systems. And the important energy savings go hand in hand with other benefits:

  • lower maintenance costs
  • lower waste-disposal costs
  • better ergonomics
  • better light


Picture: dena

Air-Conditioning Technology

Air-conditioning technology is technology that creates and maintains comfortable ambient conditions in a room in terms of temperature, humidity and air quality. This includes air-conditioning systems that convey heat into (heating systems) or out of (cooling systems) a room (for example, using airflow or ventilation technology) or systems that increase or reduce humidity by conducting air or water as heat carriers.

Picture: BMWi

When planning to construct a new building, it makes sense to install an air-conditioning system tailored to suit the requirements of the specific building. The operating costs should also be as low as possible and the energy used as efficiently as possible. Most importantly of all, regulation and control of the various technologies used should be co-ordinated as efficiently as possible.

Air conditioning based on efficient systems and renewable energies can be very energy-efficient. German companies have expertise in the two key areas, which are outlined below:

Heat recovery ventilation (HRV)

With heat recovery ventilation, the energy content of the air extracted by the ventilation system is used to heat the air entering the building. The fresh air supply is usually pre-warmed during cold weather. During warm weather, particularly efficient ventilation systems use the evaporative heat loss to cool the air supply. Another option is heat recovery from waste water. For example, warm waste water (from showering etc.) can be used by heat exchangers to heat cold water, thereby saving energy, costs and CO2 emissions.

Solar cooling

In addition to the solar energy that can be used to heat water and support room heating, any excess energy generated during the summer months can be used to cool a building. This approach works well because a building's cooling requirement increases in tandem with the amount of solar energy that can be generated, which means that the greatest cooling effects can be achieved when they are most needed. For this purpose, a thermal cooling machine can be used in conjunction with a solar heating system. Unlike conventional cooling machines (i.e. compression cooling machines), this uses a thermal compressor. The advantages of these machines over conventional cooling machines are that cooling agents, which are harmful to the environment, are not required and that environmental heat instead of valuable energy (usually electricity) is used to operate the compressor.


Picture: Solarpraxis

Combining Building Technologies to Best Effect

The greatest energy efficiency is achieved by combining various energy-efficient technologies. Of course, competent planning and selection of measures, and their careful execution, are absolutely essential. The special provisions in German legislation encourage full utilisation of the scope and potential of these technologies and promote diversity in the approaches used. As a result, German engineers are driving the energy-efficient merging of insulation and heating technology and the development of the necessary control systems. German companies are global leaders in energy-efficient boiler technology, renewable energies and control systems, offering the greatest number of solutions and the most advanced.

Examples include: 

Buildings with optimised insulation, such as passive houses, are virtually air-tight. In these buildings, ventilation systems provide the hygienically required air renewal and maintain a constantly optimised quality of air, while minimizing the supplementary heat requirement. A central ventilation system is an ideal solution for utilising the heat in the extracted air to pre-warm the incoming fresh air. Air-to-air heat pumps can reduce the ventilation heat requirement by up to 95%, for example.

Where solar radiation (which is free of charge and of CO2) is used as an energy source, an intelligent combination of technologies involving heat stores and heat generators provides the solution for periods of low sunlight:

  • Well-insulated heat storage tanks with a tall and narrow design and minimised heat stratification, used in conjunction with intelligent control technology, enable the use of various levels of heat and the storage of heat from various sources, while keeping heat loss to a minimum. These are used both by the solar heating system and by the secondary heat generator, for example a pellet or condensing boiler or a heat pump in order to reduce partial-load conditions or cycling.
  • Other storage solutions are also available. The structure of the building itself can balance day/night differences if the thermal mass of its components is activated (for example, with water pipes in the ceiling). In addition, latent heat storage (with PCM, or phase change materials), such as encapsulated paraffin in the surface of interior walls (for example, plaster, gypsum plasterboard or chipboard) can maintain the desired temperature over longer periods.

In terms of systems engineering, geothermal probes significantly enhance the potential of solar heating systems and heat pumps. During the summer months, the soil around the probes can be regenerated using the surplus heat from the solar heating system. This type of coupling also protects the solar unit against stagnation, which would damage its components. During the summer, solar units can normally provide a building's entire hot water requirement, which saves heating costs and, of course, reduces CO2 emissions.

Pellet boilers and condensing boilers can similarly be used in combination with solar heating systems. By having these boilers provide almost all of the hot drinking water required during the summer months, inefficient partial-load conditions are avoided. This protects the environment, reduces costs and enhances the durability of the boilers themselves.