advanced office buildings with efficient … office buildings with efficient technologies in...

© Copyright 2001-2002 Rahul Walawalkar, Dr. Amitabha De, Trupti Mogare, Jyotika Sahariya 1 of 1

Advanced office buildings with efficient technologies in Frankfurt am Main

Dr. Werner Neumann City of Frankfurt am Main – Energiereferat – Municipal energy agency Galvanistrasse 28 D 60486 Frankfurt am Main Email: [email protected]

Keywords Office buildings, efficiency, integral planning, primary energy, banks, high rise building

Abstract How to construct a low energy office especially in high rise buildings has become an important task. Recent studies of the City of Frankfurt have shown, that the specific primary energy demand may vary between 200 and 1000 kWh/m2 * year, dependent on different comfort levels and efficiency of installed equipment. (average value 500 kWh/m2) The results of this study will be presented in another report on the IEEBC conference. Since 1990 there is an interesting development towards a more efficient use of energy in office buildings. The planning methods have changed and new technologies will reduce the energy demand of new office buildings significantly by a factor of 4 and more related to existing office buildings.

Background The electricity demand is an important part of the total energy demand in Europe. Electricity is the dominating factor of the energy demand in office buildings. There is a high potential of efficiency in existing office buildings. It will be shown how the energy demand of new office buildings has dropped significantly in the last decade. This will be an important contribution to the European Commissions aims for reducing CO2-emissions and the security of European energy supply.

Reduction of primary energy demand in advanced office building Until the year 1990 high rise office buildings have been constructed with a totally closed façade combined with internal heat- , ventilation- and air conditioning- (HVAC) systems. In the past it has been the main guideline that office rooms should be independent of the outside climate and weather conditions. The Frankfurt Fair Tower (next to the Frankfurt fair) constructed at the end of the 90ties, seems to be the last high rise building of this “generation” of office buildings. The façade is closed airtight and there is an air conditioning system with induction air inlet together with a four-rod static heating and cooling device. But there was no central energy management system and users could heat and cool simultaneously in the same room. A black sun shading at the inside of the window sometimes acts like a solar collector, not keeping heat outside, but in contrary heating up the office rooms. At the opening of the building, the design temperature was set to 21°C for summer and winter. All these features cause a very high energy demand for heating and cooling. (Meanwhile some of this mistakes have been corrected) Nevertheless, the supply of energy is rather efficient, by steam transmission from a local CHP station, combined with absorption cooling.

In the year 1990 the City of Frankfurt on the Main joined the network of the "Climate alliance of European cities" – (an alliance of more than 1000 cities in Europe) as a founding member. This City network has set up the objective of reducing the CO2 -emissions by 50% until the year 2010. Therefore, it has attached great importance to ensure that new buildings have a low energy demand. Starting in the year 1992 there have been several plans for new high rise buildings. The City’s aim has been to reduce this additional energy demand. The Commerzbank, one of the biggest German banks, has set up the goal for an energy saving and ecological building as well. It became clear, that the main issue of ecology in office buildings is


the energy demand. In the final outcome, it turned out that the highest office building in Europe has been designed with an energy demand 30% less than in the first planning stage.

In January 1993 the Environmental Department and the Municipal Energy Agency ("Energiereferat”) of the City of Frankfurt founded the "Energy forum for banks and offices", starting with an information meeting for investors, architects and planning consultants and the formation of a working group with the responsible persons of four projects. We invited experts from Switzerland, because there has been specialized experience on planning methods to reduce the electricity demand in office buildings.

At first glance the aims of the city to protect the environment and to reduce the CO2 emissions differ substantially from the investor’s aims. The city tries to reduce CO2 emissions in order to combat global warming. Rising temperatures on our planet will lead to weather and climate changes, floods, aridity. The big insurance companies are fully aware of the problems which will arise from climate changes. This awareness is based on reliable scientific results. By contrast, private investors are not concerned about this problems. They want to construct buildings with good comfort, often combined with high cooling demand and the price of the building should be low compared to the general building standard. Especially for investment funds, which will sell or let buildings and often do not know the future tenants´ demands, energy demand plays almost no role at all. Energy costs are only a very tiny part of the total costs for an employee’s working place incl. salaries. But now in some offices the costs for energy, water, maintenance and facility management of the building have reached significant levels, and are called the „second rent“. With a higher supply of free office rooms in Frankfurt and dropping rents for offices the demand of energy has got a higher significance. Low energy demand may also be a form of insurance against higher energy prices in future. This argument is getting more important for investors, who will mainly use a new building for their own employees.

National laws setting limits to energy demand exist only for heating demand but there are no limits to an extraordinary consumption of electricity. We therefore offered advice for investors, architects and planning consultants and started a common action on a voluntary basis. We asked: „How much energy will your building need?“ and showed ways to calculate this. It may be astonishing - that in most cases this calculations have not carried out previously. Everyone knows about the power demand measured in kilowatts of the equipment to be installed, but nobody cares about the amount of energy which will be consumed in future. But if this aspect is taken into account, a wide field for the optimization of the building’s equipment will open. We therefore offer data sheets to calculate the future energy demand and floor-space specific data (kWh/m2), and it emerged that there can be great differences. Meanwhile a list of benchmarking values for the different purposes of energy consumption has been established, which can be used to compare different buildings or different planning approaches. The Swiss standard SIA 380/4 on electricity demand has been our guideline. Software to use this standard is now available. We can recommend that everybody should use this standard or adapt it to national conditions. We actually have launched a SAVE proposal to disseminate the experience of electricity saving in office buildings integrated with the purchase of green electricity.

The most important way to efficient office buildings is the method of so called “integral planning”. Typically all different parts of an office building are planned in a separate way by different planning teams – façade, heating system, cooling, air conditioning, lighting, office equipment and the energy supply system. This results in an oversize of all components. Potentials to save energy remain invisible, because the different planning teams only look for their specialized part.

In integral planning, there will be an additional planning consultant responsible to integrate the different parts. The façade of the building will be optimized for low heat losses and high gains of daylight, but low external heat gain. This will reduce both heating, cooling and lighting demand. The lighting installations have high efficiency lamps with electronic ballasts, a daylight control and an occupancy control. Thus a lower installed specific power for lighting is combined with lower running costs. Lower electricity demand for lighting, reduces the cooling demand. Lower electricity demand for office equipment (flat screen monitors) and switching off stand-by losses have the same result. Briefly one can say, that saving a kilowatthour of lighting and other equipment will save another kWh in cooling and air conditioning demand. The investment costs for an advanced façade may be higher, but there will be a significant saving in the HVAC system. It will be necessary to integrate the future running costs into the optimization of the


construction. In an inefficient building the running costs of a building over 20 years may be higher than the construction costs.

The Commerzbank tower (architect, Sir Norman Foster, London - up to now the highest office building in Europe – 299 m) has integrated all of these features of integral planning. The most important difference to the old fashioned type of office buildings has been a new designed façade, where the windows can be opened to let fresh air in. If the window is opened, heating, cooling and ventilation devices will be automatically shut off, resulting in a reduced energy demand. The facade has an unglazed wall base, which has better insulation than glazing and reduces heat from the sun. The window consists of two window-panes, whereby the inner one may by opened and between the inner and outer pane air may circulate, thus dissipating heat in summer. Between the window-panes a variable blind can control light and reflect outer heat. In comparison so-called "solar facades" may produce more cooling problems by capturing solar heat than they solve. The window can be controlled individually by the employees and in case of stormy weather, all windows will be closed automatically.

Figure 1. Commerzbank tower, Frankfurt am Main

In the same way one can optimize the electricity demand for lighting. A usual standard is to have a level of 500 lux for a working place in offices. But nowhere it is recommended, that this level should be reached in every corner of your office. Therefore it turned out, that 300 lux for general lighting may be sufficient and only on the desk 500 lux should be reached. It is easy to understand, that you will save a lot of lamps and a lot of electrical power. Often it is more appropriate to have a uneven distributed lighting rather than a constant light level in all parts of the room, especially for computing working places.

After the Commerzbank Tower has been constructed with this new window construction, in the Main Tower another approach was chosen. The windows can be opened by shifting the window to the outside. Additionally in the Main Tower the heating and cooling system is connected to an underground thermal storage, with heat exchanging tubes placed in the ground underneath. Some parts of the stored heat from summer (cooling) can be used in winter for heating purposes. The supply of heat and electricity comes from an on-site combined heat and power plant, which will reduce the primary energy demand by 30%.


Figure 2: Sectional drawing of improved window design

Two new approaches to window constructions in Frankfurt high rise buildings, left “Main-Tower”, right “Commerzbank Tower” (drawing by courtesy of E. Kaiser, Frankfurter Allgemeine Zeitung, Aug, 18th, 1998) The picture shows two approaches to new window constructions of the new high rise office buildings in Frankfurt am Main. In one case the inner part is a tilting window, in the other case a part of the window is a ventipane, which is shifted to the outside.

Meanwhile is has become state of the art to construct the façade of office buildings in a similar way as these two avant-garde buildings.

In the Commerzbank tower, the energy demand was reduced by 30% in comparison to the very first planning. Then the method of integral planning has been applied i.e. of the new police head quarter in Frankfurt. It turned out, that by redesigning the first planning for electricity (lighting, air conditioning etc.) the electricity demand could be reduced by 50% with 1 Mio. Euro less investment costs. This shows how powerful the method of integral planning may work, reducing investment costs in the same way as future running costs and reducing the environmental impact of CO2-emissions.

Most of these new office buildings have an energy supply by combined heat and power. In some cases the heat is delivered by a heat transmission line from a central heat and power station. In other cases (European central bank, Main Tower, KfW-Bank, Federal Bank of Germany) there is a CHP power plant as an integrated part of the building. A detailed report on CHP will be held in another section of the IEEBC.

These buildings show that starting with conventional planning methods a reduction of 30-50% of the energy demand is possible, if the method of integral planning is applied. But starting with the new century a new generation of even more efficient office buildings was born.

The new office building of the Helvetia insurance company in Frankfurt was designed as a low energy office building as one of the important objectives. The outer façade is completely glazed with a triple pane glazing. The type of glazing reduces the transmission of infrared light and is sufficient for daylight use. This type of glazing reduces both heat losses in winter and heat gains in summer. The building has no separate heating and cooling system. Heating and cooling supply are integrated in a system of long tubes


distributed in the concrete of the floor and the ceiling. Water flowing through these tubes has only a little temperature difference to the wanted room temperature (+ 3°C in winter, - 3 °C in summer). Due to the big surface of heat exchange and the heat capacity of the concrete this system ensures a smooth, self regulated heating and cooling at a very low level of consumption based on the good insulation of the building. The heat energy demand of the Helvetia building is only 25 kWh/m2*year compared to a typical value of 150-200 kWh/m2*year in other office buildings. Obviously there are high efficient lighting systems with direct/indirect lighting and the primary energy will be in range of only 150 kWh/m2*year including office equipment. Some hundreds of measurement devices document the temperature and energy flows in this building. The additional costs for measurements were financed by a local subsidy program in Frankfurt.

Another new office building in Frankfurt just under construction will have a primary energy demand of only 100 kWh/m2*year (office equipment not included). This aim was set up by the KfW-Kreditanstalt für Wiederaufbau, the federal based German subsidy credits bank of Germany. The KfW offers credits with low interest rate for enterprises and private persons for environmental projects, energy saving and renewable energies (100.000 solar roof program). Now the KfW has decided to implement energy saving and renewable energy in their own new office building. As in other cases there will be an optimized façade, windows can be opened, heat recovery, efficient lighting systems and efficient office equipment. Additionally the heat will be delivered from a wood pellets boiler, which will provide 100% CO2-free renewable energy from biomass. (pellets = pressed pieces of sawmill dust). This will be the first pellets-boiler in an office building with this size. In another existing office building the KfW runs a CHP plant with absorption cooling with a high efficiency.

The examples show that there is no typical way to low energy office buildings, but if the investor wants to have a low energy building, all different building designs of architects can be transformed to a low energy level. New office buildings can have an energy demand less by a factor of 4 to the average of existing office buildings.

Summary First the investor has to decide on the comfort level which is wanted. The inside temperature may vary proportional with the outside temperature (max. 26/28°C), still ensuring a good comfort level esp. in summer. This will reduce cooling demand.

The architects work will be to optimize the façade for low heat losses in winter, low heat gains in summer and variable shading.

A specialized consultant should integrate the different parts of planning relevant for the energy demand (heating, cooling, lighting, air conditioning, ventilation etc.) and will set up a forecast of the future energy demand and costs.

A significant reduced energy demand can be provided by combined heat and power plants, absorption cooling. In future time renewable energies will play a more important role.

This is the basis, that the building will be prepared for a Facility Management System, which not only will integrate energy and water demand but all other parts of FM.

The conclusion is, that efficient office buildings combine a good comfort level with a low energy demand and can be combined with new flexible models of office organizational schemes.

References Dr. Werner Neumann - New ways towards ecological offices - More office and less energy - Conference "Electricity Efficiency in commercial buildings“ , Amsterdam, Sept. 21-23, 1998 Dr. Werner Neumann – Integrated design of office buildings Conference „Promoting greater energy efficiency in buildings – Bruxelles – Oct. 12th, 2001

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ENERGIEREFERAT

STADT FRANKFURT AM MAIN Dezernat für Bildung, Umwelt und Frauen

Advanced office buildings in Frankfurt am Main

Dr. Werner NeumannMunicipal Energy AgencyCity of Frankfurt am Main

2nd International Conference on Energy Efficiency in Commercial BuildingsNice, May 2002

Folie 2 Mai-02

Climate Protection in Frankfurt am Main


Energiereferat 79A

High potential for reducing energy demand in office buildings

Primary energy from 200-1000 kWh/m2

Cities aim as member of Climate Alliance to reduce energy demand and CO2-emissions1990 first project of an energy efficient high rise building (Commerzbank)Meanwhile planning process has changedEnergy and CO2 will be intregrated in architecture and planning of equipment

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Folie 3 Mai-02



Energiereferat 79A

The usual way – non-integrated planning of buildings

Usually the different parts of a building are planned and designed separately:

facade, shading, windows, insulationheating, cooling, ventilation, air-conditionlightingoffice equipmentenergy supply, boiler, CHP, solar energy

Folie 4 Mai-02



Energiereferat 79A

BUT – many parts have influence on other parts of the building

better insulation reduces heat demandbetter shading reduces cooling demandbetter use of daylight reduces electrical lighting demandbetter daylight and occupancy control reduces electricity demandmore efficient lighting reduces cooling demand etc etc etc....

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Folie 5 Mai-02



Energiereferat 79A

The main part of the work : integration

variation of parameters – optimizationset up guidelines for efficiencyhigher investments in one part will give higher savings in another partoptimization is „contraproductive“ for the interests of separated planners the architect should be the „integrator“ but mostly does not fulfil this duty

Folie 6 Mai-02



Energiereferat 79A

Calculation of electricity demandSeperate building into zones of same type of usage and different types of purposes

40 W/m2300 kWh/m2

0 W/m210 W/qm10 kWh/m2

Office equipment

30 W/m2100 kWh/m2

0 W/m220W/m24 kWh/m2

Cooling

12 W/m210 kWh/m2

5 W/m24 kWh/qm

7 W/m26 kWh/m2

Lighting

computingfloorsoffice rooms

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Folie 7 Mai-02



Energiereferat 79A

Folie 8 Mai-02



Energiereferat 79A

New types of facades of office

buildings in Frankfurt

Left: Main Tower

Right: Commerzbank

Windows can be opened reducing air-conditioningand ventilation

demand

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Folie 9 Mai-02



Energiereferat 79A

Another new approach: facility management

start with the question of energy demand and total costs of the buildingtotal costs are construction costs plus lifetime costs (notice!: the last ones are higher!)what will be the „second rent“ ?will the building be „variable“ and be comfortable?will the building have an energy management?construct the building starting from the „inside“!

Folie 10 Mai-02



Energiereferat 79A

A new „philosophy“ of buildings

set up ecological and economical guidelinesdefine the comfort level of the buildingset standards of efficient equipmentcalculate future energy demand optimization of facade and architecturestart the process again and again

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Folie 11 Mai-02



Energiereferat 79A

The result – a new generation ofenergy efficient buildings

Commerzbank: 30% less energy demand, new facade design, district heat, absorption coolingNew police headquarter: 50% less electricitymit 1 M € less investmentMain Tower: new facade design, underground heating/cooling storageHelvetia Insurance: low energy building, < 25 kWh/m2 heat, triple glazing, efficient lighting, self regulating heating/cooling in floor/ceiling

Folie 12 Mai-02



Energiereferat 79A

Continued....

KfW-Bank: planned < 100 kWh/m2 primary energy demand, wood pellets boilerEuropean Central Bank, German Federal Bank, KfW-Bank, Main Tower: CHP on site electricity generation with absorption cooling

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Folie 13 Mai-02



Energiereferat 79A

On the way to efficient buildings Investor has to define comfort levelArchitect has to optimize facade designSpecial consultants integrate demand and supply side with architectural designUse most efficient equipmentDemand should be covered by CHPThe building should be prepared for „facility management“ Reducing energy demand will save both investmentand running costsContribution to Kyoto aims of Climate Protection

Folie 14 Mai-02



Energiereferat 79A

Benchmarking of existing office buildings

Comparison of total energy demand of 13 office buildings in Frankfurt Implementing Energy Controlling Identifying Saving Potentials Specific values make buildings comparableMinus 25% of demand is possible

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Folie 15 Mai-02



Energiereferat 79A

Primärenergieverbrauch

0

200

400

600

800

1 000

1 200

1 9 KFW Ost 12 3 5 13 8 2 4 10 11 7 6

< 20m < 20m < 20m 20 - 60m 20 - 60m > 60m > 60m < 20m < 20m > 60m 20 - 60m < 20m < 20m > 60m

vor 90 vor 90 i. P. vor 90 nach 90 nach 90 nach 90 nach 90 vor 90 nach 90 vor 90 vor 90 nach 90 vor 90

˜ ˜ ˜ ˜ ˜ ˜ ˜ ˜ ˜ ˜ ˜

Objekt

kWh

pro

m2 E

nerg

iebe

zugs

fläch

e (E

BF) u

nd J

ahr Wärmeenergie

Nicht zugeordnetDiverse TechnikLüftung/KlimaBeleuchtungZentrale DiensteArbeitshilfen

„Faktor 4“ - Primary Energy Demand

of Office Buildings

Folie 16 Mai-02



Energiereferat 79A

New: electronic ballasts for retroFIT of existing office buildings

SAVE IT EASY

Minus 30%

EASY 2 FIT

Minus 40%

advanced office buildings with efficient … office buildings with efficient technologies in...

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