The starting point. Energy is no issue in non-residential buildings

In the European Union commercial buildings (non-residential buildings) consume more than 25% of all end energy used, causing a rising level of carbon emissions and rising energy costs. But, there is little effort and apparent incentives to design and build new commercial buildings with substantially lower energy consumption than usual. In the last years local initiatives and european projects have developed new methodologies to analyse the energy demand. Several new commercial buildings have been constructed in a low energy way. Reducing energy demand, efficient combined heat and power and integrating renewable energy. Low energy buildings are economical to construct, have lower cost to operate and are more comfortable.

Ways to recognize the energy problem

There are many reasons, why energy issues are not well integrated in the planning process of non-residential buildings. Even with rising prices, energy costs are only a relative small fraction of the overall costs of a building as capital costs/rent, maintenance, cleaning, security etc. and an even much lower part, when compared to the total cost of a working place including salaries.

A crucial point is the disintegration of energy aspects in the design and architecture competitions for new high rise buildings. The architecture defines shape and the outer façade of the building, but mostly it is not clear that “by the way” the architect decides on the energy demand with several decisions about the façade.

The next step, the planning of the installations for lighting, heat ventilation air conditioning (HVAC) etc. are typically made separately. To meet certain requirements and comfort conditions the installations get more expansive to “fight” against the unchangeable decisions from the architect´s side. The main problem is the lack of transparency and an open iterative procedure to find better solutions. An intrinsic obstacle is that the planners fee is proportional to the installed power of energy consuming systems. Oversizing is also the answer to the problem of guarantee.

The primary energy is the benchmark

As a first reaction to the energy problem in office buildings a movement of architects started towards “solar architecture” in the mid 1990(Behnisch, Herzog,…). But that the sun delivers (heat-) energy for free to save heating fuels, can turn into contrary especially in high rise office buildings with huge totally glazed facades, causing a high demand for cooling. Even more critical – electricity for cooling chillers and other purposes are sometimes not treated as “energy” because planners only think about heat or electricity is not seen as an environmental and cost problem. Therefore it is recommended to focus on the “primary energy” which integrates all energies from the well and mine to the building including losses of 50-70% in electricity production from nuclear and fossile condensing power stations.

As a result, energy efficiency issues are not treated well and are sometimes actively ignored. Even worse, bad experiences of the using phase are held top secret, not to run into regress quarrels with the architect and other equipment planners. Therefore there is nearly no feed back from failures and not enough presentation of success stories.

Huge differences in energy demand in high rise buildings

With rising energy prices as a “second rent” of office buildings and the political decisions to reduce the CO2-emissions and the energy dependency some initiatives have started to analyse the energy demand in detail since 1995. In a “benchmarking” comparison in Frankfurt am Main it turned out, that the range of primary energy comsumption (electricity*3 + heat) laid between 1000 kWh/m2*a (1970, fully closed façade and climatisation), 400 kWh/m2*a (1980-1990, semi climatisation) and 100-200 kWh/m2*a for new office buildings. Interesting, that the building air conditions and the users comfort is mostly better in modern low energy buildings.

Typically the next question is, if the additional costs for “energy efficiency investments” are economical within some years. This question is typically posed by investment companies, whereas in contrary “self user”-investors (banks, insurances) have a longer time scale (> 30 y) for amortisation and have turned out as forrunners of low energy office/high rise buildings. In some cases the investment costs for energy efficient buildings were lower, because optimisation of the façade, lower energy demand gave the possibility to reduce ventilation and cooling equipement or to turn to free cooling.

European directive gives new impulses

Knowing that electricity has a high impact on the environment (nuclear risk and waste, electricity from coal causes 40% of CO2-emissions in Germany), the European Directive on the energy perfomance of buildings gave new impulses. Based on the primary demand including electricity for lighting, ventilation, cooling, the land lords of buildings have to present an energy certificate (kWh/sq.m) together with recommendations for improvements. All EU member states have to implement this directive, but 25 different schemes turned out. Informative labels show both the energy demand under standard conditions and the real actual consumption.

Energy Performance Certificate

An example

Technical ways to low energy buildings

Technical improvements of low energy buildings are:

• Reducing the part of glazed façade elements;
• Double windows with internal shading;
• Concepts of free cooling at night;
• Thermoactive concrete ceilings as a self regulating heating and cooling system;
• High efficiency technologies in all fields as lighting, pumps, ventilation;
• User friendly controls combined with a building and energy management system;
• High efficient cogeneration for heat and electricity, sometimes with absorption cooling using waste heat in summer;
• Integration of renewable energies, as photovoltaics on wall and roof, heat recovery with heat pumps, wood pellets (grenules à bois) for heating.

Organisatorial ways to low energy buildings

Much more important than the technical components is the organisation of planning and construction. The main decision must come from the investor´s side. The top management must say “we want to have an energy efficient building, with less than 150 kWh/m2*a ”. This must be part of the architectures competition. Parallel to architectural and technical planning an “energy survey” must make sure, that the energy target is constantly calculated and controlled. Because some of the new calculation schemes (DIN 18599 (D), CEN-standards) are not easy to applicate to complex office and high rise buildings, it is recommended to run building simulation codes or even to construct model rooms with measurements.

To tackle the problems of incompetence of a separated planning process, the energy team should have a high responsibility towards other planning parts and should control and guarantee the energy target values in the first 2-3 years of usage. Such a kind of buildings must be eingefahren.

Shining examples

In Frankfurt am Main some good examples of low energy high rise buildings can be presented. First of all the “Commerzbank Tower” was the first high rise building, where windows can be opened in a height of more than 200 m. The energy demand for cooling and heating was dropped significantly. The Helvetia Insurance constructed a low energy building with less than 25 kWh/m2*a heating demand. The “KfW-Bank” (German state funding bank) constructed a very low energy building with less than 100 kWh/m2*a. Even without any active cooling the room temperatures could be held below 26° in summer 2003. Now the KfW has used this experience in a refurbishment project and two other projects of new low energy buildings. The target is to have a primary energy demand below 100 kWh/m2*a and more than 1/3 is delivered by renewable energies as solar power or biomass.

Commerzbank Tower

Frankfurt am Main

KfW Bank

Farnkfurt am Main