EXAMINATION OF LOW ENERGY RETROFIT MEASURES IN A DANISH, A GERMAN AND A GREEK OFFICE BUILDING

Transcription

1 EXAMINATION OF LOW ENERGY RETROFIT MEASURES IN A DANISH, A GERMAN AND A GREEK OFFICE BUILDING Niels-Ulrik Kofoed Esbensen Consulting Engineers, Vesterbrogade 124 B, Copenhagen, 1620 V, Denmark, Phone: , Fax: , n.u.kofoed@esbensen.dk Abstract This paper describes results from the EU project OFFICE - Passive Retrofitting of Office Buildings to Improve their Energy Performance and Indoor Working Conditions funded by the European Commission under the 1995 JOULE III Program. The objective of the OFFICE project was to promote passive solar and energy efficient retrofitting measures in office buildings. Ten European office buildings were included in the project situated in England, France, Greece, Italy, Norway, Denmark, Sweden, Germany and Switzerland. The retrofitting techniques examined include activities on three levels- measures, scenarios and packages. These were simulated using a number of exact and validated building simulation tools. The results reported were annual energy demands for the varies energy services (space heating, hot water, cooling, ventilation, lighting, equipment), economy (saved energy cost, saved running costs, capital costs, simple pay back period and present value of investment) and thermal comfort (overheating). In this paper, selected results from the Danish, the German and the Greek case study buildings are presented. The result when the package is implemented in the Danish building is that the total annual energy demand is reduced from 331 kwh/m² to 95 kwh/m² (71%). For the German package the result is that the total annual energy demand is reduced from 273 kwh/m² to 72 kwh/m² (74%). Finally, the total annual energy demand is reduced from 347 kwh/m² to 124 kwh/m² (64%) for the Greek package. The calculated present values are for all three packages positive, showing that it is profitable to carry out the retrofitting actions as proposed. 1. INTRODUCTION This paper describes selected results from the EU project OFFICE - Passive Retrofitting of Office Buildings to Improve their Energy Performance and Indoor Working Conditions funded by the European Commission under the 1995 JOULE III Program. The objective of the OFFICE project was to promote passive solar and energy efficient retrofitting measures in office buildings, while still maintaining satisfactory indoor conditions. This was done by examining different low energy retrofitting techniques and, based on this, global retrofitting strategies and design guidelines were developed. Ten European office buildings were included in the project situated in England, France, Greece, Italy, Norway, Denmark, Sweden, Germany and Switzerland. 2. METHODOLOGY The OFFICE project group was divided into three subgroups: The Experimental subgroup The Design and Evaluation subgroup The Design Guidelines subgroup The objectives of the experimental subgroup was to take care of the selection of case study buildings and registration of the selected buildings (through building audits). In addition the group supervised the short term and the long term monitoring campaigns completed for each of the buildings. The objectives of the Design and Evaluation subgroup partly was to help selecting appropriate retrofit measures for the case study buildings and partly to supervise the evaluation of these. The objectives of the Design Guidelines subgroup was to prepare a Design Handbook, a so-called Atlas and two different rating methodologies for assessing office refurbishment. The Design Hand, available from James & James during year 2000, contain a comprehensive description of different subjects related to retrofitting of office buildings. Subjects are for example heating, ventilation, daylight, cooling, Building Management Systems (BMS), acoustic, fire safety and simulation tools. The Atlas presents the results of an examination, where varies retrofit measures have been examined under different European climatic conditions. The work in the OFFICE project ran from 1995 to 1999 and went through the following nine main phases:

2 1. Selection of one case study building per country (two from Switzerland). 2. Registration of buildings concerning constructions, systems and user profiles. 3. Completion of short term and long term monitoring campaigns including occupant surveys. 4. Validation of simulation tools using the monitoring results. 5. Planning, evaluation and reporting of retrofit measures for each of the buildings under local climatic conditions. 6. Evaluation and reporting of the most important retrofit measures for each of the buildings under other European climatic conditions (Atlas). 7. Completion of a Design Handbook based on the results from paragraph Completion of the Atlas based on the results from paragraph Completion of the two rating methodologies including exemplification of the methods based on the results from paragraph CASE STUDY BUILDINGS The ten case study buildings were selected from an initial set of three candidates from each of the countries participating in the project. The selection was based on the basic requirement, that each of the buildings should represent a typical type of national office building ready for retrofit. In this way it could be secured, that building types with as large retrofit potential as possible were chosen. In addition the group of buildings should represent the maximum possible variety with regard to type and pattern of use. The ten buildings are listed in table 1. The ten case study buildings can be classified in five main types: Free standing, core oriented, mostly open plan, heavy structure (Athens, Florence) Free standing, skin oriented, mostly cellular, heavy structure (Bern, Copenhagen, Trondheim) Free standing, skin oriented, mostly cellular, light structure (Berlin) Enclosed, skin oriented, cellular, heavy structure (London, Lausanne, Lyon) Enclosed, skin oriented, cellular, light structure (Gothenburg) To take into account the very different climatic conditions in Europe, the buildings were selected from a wide range of climates: North European coastal (Copenhagen, Gothenburg, Trondheim) Mid European coastal (London) Continental (Berlin, Bern, Lausanne, Lyon) Southern Mediterranean (Athens, Florence) The buildings also represent very different energy demand profiles. This can be seen from the total energy demand of the buildings, which vary from 94 to 717 kwh/m² per year. Part of this is due to climatic differences, but the age and the function of the building has a vital influence too. 3. CALIBRATION OF SIMULATION MODELS A number of exact and validated building simulation tools have been used to simulate the proposed retrofitting measures, scenarios and packages. For energy studies, TRNSYS, DOE, ESP, TAS, Tsbi3, and SUNCODE have been used. For daylight studies, RADIANCE, SUPERLIGHT, and PASSPORT-Light have been used. It was actually proposed, that all design teams should use the same type of simulation tools. However, due to costs of such a procedure, it was decided to let the design teams use familiar design tools. Name of Year of Area: gross / Number of Location building erection conditioned [m²] occupants 1 Danfoss Headquarter Nordborg, Denmark ,400 / 7, Krokslätt Gothenburg, Sweden ,971 / 29, Postbank Berlin Berlin, Germany ,200 / 11, Sentralbygg I Trondheim, Norway ,440 / 6, Central and West House London, UK / City West Bern, Switzerland / LESO Lausanne, Switzerland / Cassa di Risparmio Florence, Italy ,872 / 1, Aget-Heraklis Athens, Greece ,292 / 6, Le Recamier Lyon, France ,040 / 4, Table 1. List of case study buildings in the OFFICE project.

3 As it was of vital importance for the OFFICE Project to base guidelines on well validated results, the building models were calibrated against monitored data on energy consumption and temperature pattern. The monitored data used in the calibration process were short term monitoring results from the summer 1997 and the winter The short term monitored data can be divided into two main types - Building specific data and Meteorological data. Building specific data includes measured energy demand and measured building temperatures e.g. room temperatures. The building specific data were utilized as basis for comparison with the simulated results and as basis for checking the input data for the building model. The meteorological data were used to create the weather files for the simulation tools. Most of the meteorological data were in fact, provided from nearby meteorological stations and not monitored on site. Retrofit measures in the OFFICE Project Case Study building Improve thermal insulation of opaque elements X X X X X X X X X Replace window frames in bad condition X X X X X X X X Improve insulation standard of window panes X X X X X X X X Reduce infiltration rate X X X X X X X Use of mass walls, solar walls, atria or double facades X X X X Use of reflective blinds or light shelves X X X Use of effective solar shading systems X X X X X X X X X X Use of night ventilation X X X X X X X X X X Use of exposed thermal mass X X X Use of ceiling fans X X X X X Use of indirect evaporative cooling X X X X Use of natural ventilation X X X X Use of solar protective glazing X X Daylight responsive control of artificial lighting X X X X X X X X Control of artificial lighting in response to occupancy X X X Use of HF-ballasts X X X X X Use of modern luminaries or reflectors X X X X Use of task lighting X X Reduction in installed power for lighting X X Use of heat recovery on ventilation air X X X X X Reduce ventilation rates X X X Reduce running time of mechanical ventilation X X Improve fan efficiency X X X X Improve mechanical cooling machines X X X Use of heat recovery from condenser coil X X Use of water reservoir for free cooling or for heat sink X X Use of efficient boiler system X X X Use of heat recovery from flue gases X X Improve HVAC distribution system X Reduce heating set-point X X X Increase cooling set-point X X Table 2. List of measures examined in the OFFICE project.

4 Some of the important experiences arising from the calibration process were: It was difficult (costly) to measure the different energy services separately. For example to separate total electricity demand into demand for lighting and office equipment. This made calibration of some of the energy services somewhat difficult and emphasizes, that building systems should be designed for monitoring, if results should be of high quality. The calibration process showed that often the official data concerning set-points and time schedules for the building services, did not correspond with the data used in reality. This highlights the need for better commissioning and quality control of such systems. With all the uncertainties involved in a simulation process it is almost impossible to obtain close accordance between simulated and measured results (especially energy results). Therefore, it is usually more important to calibrate simulation tools according to energy patterns than according to actual energy figures. 4. RETROFITTING TECHNIQUES The ten case study buildings were thoroughly investigated through energy audits and through short term and long term monitoring campaigns. Based on these activities, specific retrofitting techniques were chosen for each of the buildings. The techniques all aim at improving energy performance and indoor environment, using both passive solar techniques and energy conservation techniques. The examined retrofitting techniques include activities on three levels: Measures Scenarios Packages Measures are individual retrofitting techniques, such as improved insulation standard, use of solar shading devices and improved heating and cooling systems. In total around 30 different measures have been evaluated (see table 2). Note that the numbers in table 2 refers to the same building numbers shown in table 1. Also note that the categories in table 2 might include more than one measure. Combinations of retrofitting measures within the categories Building envelope improvements, Passive cooling techniques, Electric lighting improvements and HVAC improvements are called scenarios. Finally, combinations of the different retrofitting scenarios, which constitute an integrated retrofitting design approach, are referred to as packages. 5. EVALUATION The results reported for the measures were annual energy demands divided on energy services (space heating, hot water, cooling, ventilation, lighting, equipment), economy (saved energy cost, saved running costs, capital costs and simple payback period) and thermal comfort (overheating hours). For scenarios and packages energy demands per month, present value of investment and accumulated frequency curves for indoor and outdoor temperatures, were also reported. In total results for 136 measures, 46 scenarios and 11 packages were reported by the design teams. 5.1 Energy results The energy demands reported were gross energy demands delivered to the buildings. For electricity this equals the amount of electricity bought from the supplier to run the specific energy services e.g. the electricity needed to run the fans in the ventilation system or the electricity to run the chillers in the cooling system. Thus, the energy demands reported for cooling (chillers and fans), ventilation (fans), lighting and equipment are in most cases electricity. Space heating is in most of the case study buildings supplied through radiators, convectors or heating coils heated by circulating hot water. As for the hot water service, the heat source is usually district heating, oil or gas. In these cases gross energy demand of thermal energy, means the calorific value of the delivered district heating, oil or gas. 5.2 Economy results The saved energy costs is calculated as a multiple of the energy price and the energy saving. The energy saving is the difference between the simulated energy demand for the actual measure, scenario or package and the simulated energy demand for the reference building (existing situation). The running costs saved are the anticipated savings on maintenance due to the suggested measure, scenario or package (compared to the running costs in the reference situation). Example of such a saving is lower costs for window cleaning, when replacing non-openable windows with openable windows. The capital costs of a given measure, scenario or package is the actual investment needed to complete the retrofit. The simple payback period of a given measure, scenario or package is calculated as the capital costs of retrofitting,

5 divided with the total saving due to the retrofit compared to the reference situation. The total saving is the sum of the saved energy costs and the saved running costs. Note, that both total savings, energy savings and savings on running costs can be negative. This means, that the given measure, scenario or package actually have resulted in an increase in either the energy costs or the running costs. Simple payback period is an easy way to express the profitability of an investment (such as an investment in energy efficient retrofitting measures). However, the simple payback period method does not give an answer to whether a given result e.g. a simple payback period of 8 years, is a satisfying result. This mainly depends on the type of business the building owner is involved in. For example would some Danish housing companies be satisfied with a simple payback period of years for energy saving measures, while many production companies would prefer to invest in marketing campaigns or increased production capacity, in case the simple payback period becomes higher than 4-5 years. A better way to assess the profitability of energy saving measures is to use the present value method. The advantage of this method is that a number of economic parameters is taken into account e.g. lifetime of the measure, interest rate of alternative investment, tax rate and price rise on running costs and energy prices (due to inflation, taxes and general market development). Using the present value method, the profitability of an investment is assessed by comparing the profits (or savings) of an investment in present value with an alternative investment in for example shares. The criteria for profitability is that the present value of the investment is larger than 0. Table 3 show a spreadsheet used for the present value calculations. The figures for the Danish, the German and the Greek packages are included in the table as examples. Colored fields show input data and non-colored fields show figures, which is automatically calculated in the table. Note the differences between the key economic figures used in the calculation. In general, there is only minor differences between the figures used for Denmark and for Germany. There is, however, a clear difference between the Danish/German figures and the Greek figures. Shortly summarized the energy prices are notable lower in the Greek case, the nominal accounting interest is much higher, the tax rate is higher, the expected price rise on energy is much higher and the expected price rise on running costs is somewhat higher. In addition the savings on thermal energy and the investment necessary to complete the retrofitting package, is much lower in the Greek building than in the Danish and the German buildings. Calculation of present value Building: Danfoss HQ, Postbank Berlin and Aget Heraklis Building Packages Danfoss Postbank Aget Basic data Energy cost, electricity C Euro/kWh Energy cost, thermal C Euro/kWh Annual energy saving, electricity E kwh/m²/year Annual energy saving, thermal E kwh/m²/year 1 Input data related to scenario or package 1.1 Capital cost of measure in present value (=year 0) I Euro/ m² 1.2 Annual energy savings (year 0) = C1xE1 + C2xE2 b Euro/ m²/year 1.3 Annual savings on running costs (year 0) u Euro/ m²/year 1.4 Expected economic lifetime of scenario/package n Year 2 Economic data (all figured in decimal fraction) 2.1 Nominal accounting interest rn Tax rate for the interest rate s Expected price rise for energy ie Expected price rise in running costs iu Calculation of factual costing interests 3.1 For savings rrb For expenses rru Calculation of present value factors 4.1 For savings fnvb For expenses fnvu Calculation of the present value 5.1 Present value of savings b0 x fnvb B Euro/ m² 5.2 Present value of running costs u0 x fnvu U Euro/ m² 5.3 Capital cost in present value (from 1.1) I Euro/ m² Result: present value = B0 - U0 - I0 NU Euro/m² Table 3. Spreadsheet for calculation of present value. The low energy prices, the low saving potential and the opportunity to get a high interest in alternative investments (high nominal accounting interest) makes it more difficult to carry out profitable investments in energy saving features in the Greek building than in the Danish and the German building. On the other hand, the low capital costs due to low labor costs, the high tax rate and the high expected price rise on energy and running costs, favorites investments in energy saving features in the Greek building. All together the Greek package is more profitable than the Danish and the German packages. 5.3 Overheating hours Overheating hours is used to assess whether the thermal environment is acceptable in the case study buildings in all the examined situations. As national legislation concerning thermal comfort vary between countries, the reported overheating hours also vary. In Denmark for example, is it advised not to exceed 25 hours per year with indoor temperatures above 27 C and 100 hours per year with temperatures above 26 C (measured during the working period). This criteria is therefore used for the Danish case study building. 5.4 Areas All the results concerning energy and many of the results concerning economy are reported per square meter building. The reference area used is gross heated floor area.

6 6. RESULTS It is impossible to summarize all the results obtained in the OFFICE project on a few pages. Therefore only results for scenarios and packages for the Danish, the German and the Greek case study buildings, are presented. These three buildings represents North European coastal climate, European continental climate and South Mediterranean climate, the first and the last being the coldest and the hottest of the four climate types involved in the OF- FICE project. Danfoss Headquarter (Denmark), Postbank Berlin (Germany) and Aget-Heraklis (Greece) are multi storey buildings, which facade systems and technical systems, are in poor and outdated condition. As a result the energy demands of the buildings are very high and problems with draft, glare and overheating occur. The energy profile of the Danish and the German buildings is characterized by a very high heating demand and a relatively low cooling demand, while the Greek building is characterized by an extremely high energy demand for lighting, a very high heating demand and a high cooling demand. Table 4 shows the results for the examined scenarios and packages. Note, that the results of the OFFICE project show the consequences of retrofitting for the purpose of saving energy. In a situation where a building should be standard retrofitted anyway, the extra costs of using low energy techniques will be small, thus the investment will be more profitable, than if the building was retrofitted for energy saving purposes. 6.1 Building envelope scenario This scenario involves some of the same measures in the three buildings: Improved insulation standard of the envelope (opaque elements as well as windows) and reduced infiltration rate. In addition other heating reducing measures such as heat recovery of ventilation air, reduced ventilation rate and reduced heating set-point have been included in the Danfoss and the Postbank scenarios. Consequently, the total annual energy demand has been reduced from 331 kwh/m² to 103 kwh/m² (69%) in the Danfoss building, from 273 kwh/m² to 91 kwh/m² (67%) in the Postbank building and from 347 kwh/m² to 278 kwh/m² (20%) in the Aget building. In the Danfoss building and the Postbank building most of the saving is on the heating demand (reduced respectively 84% and 95%). The ventilation demand is reduced respectively 38% and 49%, and the cooling demand is actually increased respectively 1% and 29% in the two buildings, due to the less use of free cooling in the scenarios (lower ventilation rates). In the Aget building the cooling demand is reduced 19%, while the heating demand is reduced 30%. This puts the attention on the climatic differences between North Europe, where the main priority is to keep heat in and cold out, and South Europe where the priority is the opposite. The envelope scenarios are in all three buildings profitable, because of the positive present value of the investment. However, note that the envelope scenarios seem to be more profitable in North/middle Europe than in South Europe (when using present value as assessing method). This is a consequence of the cold climate and thus, the large potential for reducing the heating demand in North/middle Europe. Energy [kwh/m²/year] Costs [Euro/m²] Pre. Value [Euro/m²] Danfoss Headquarter Postbank Berlin Aget-Heraklis Energy Costs Pre. Value Energy Costs Pre. Value Energy Costs Pre. Value Reference building Building Envelope Passive Cooling Passive Cooling Passive Architectural Passive Architectural Electric Lighting Electric Lighting HVAC Package Table 4. Simulated results for the Danish, the German and the Greek reference buildings and for scenarios and packages (total annual gross energy demands, capital costs and Present Value).

7 6.2 Passive cooling scenario Two passive cooling scenarios have been examined for the Danfoss building. Scenario 1 combines the existing mechanical cooling system (by ventilation) with lower ventilation rates, and scenario 2 combines no mechanical cooling with the present ventilation rates. In both cases these measures are combined with an external BMS controlled solar shading system, exposed thermal mass and medium reflective openable windows, which allow for user controlled natural ventilation (venting) to assists the mechanical system. It can be seen from table 4, that the most energy efficient of the two passive scenarios are the one with mechanical cooling, where the total annual energy demand is reduced from 331 kwh/m² to 272 kwh/m² (18% saving versus 9% saving). This is due to the fact, that the energy demand for cooling already is quite low. As a consequence the energy saved by reducing ventilation rates (electricity for fans and thermal energy for pre-heating of ventilation air), are worth much more than the electricity saved by not using mechanical cooling. However, it should be emphasized, that it is not necessary to use mechanical cooling to obtain satisfactory thermal conditions in normal office buildings in North Europe. In the Postbank Berlin building the passive cooling scenario involves: Replacement of the existing clear window panes with new better insulated lightly reflective panes, increased use of night ventilation, use of a new effective BMS controlled internal solar shading system, use of a more effective lighting system controlled according to light levels (decreasing the internal heat gains), and finally, insulation of the envelope to keep heat out and cold in. The total energy demand is reduced from 273 kwh/m² to 132 kwh/m² (52%), divided on a 51% saving on the heating demand, a 57% saving on the cooling demand, a 70% saving on the ventilation demand and a 55% saving on the lighting demand. In addition to the above passive cooling scenarios two socalled Passive Architectural scenarios have been examined for the Postbank Berlin building. Except for one measure, the measures involved are exactly the same in the two cases (insulation of facade, new super low energy windows, reduced heating set-point, exposed thermal mass, effective external solar shading and automatic control of lighting). Passive Architectural scenario 1 involves using pure natural ventilation for both ventilation and passive cooling of the building (instead of using the existing mechanical ventilation- and cooling systems). In contrast to this Passive Architectural scenario 2 involves a combination of pure natural ventilation and mechanical cooling using a new installed chilled ceiling system (instead of using the existing mechanical ventilation- and cooling systems). The result is, not surprisingly, that the scenario without mechanical cooling is the most energy efficient. The total annual energy demand is reduced from 273 kwh/m² to 58 kwh/m² (79%), in contrast to a reduction to 63 kwh/m² (77%) when mechanical cooling is included. Both scenarios are profitable, even though the solution with mechanical cooling is a little less profitable, due to the high costs of the new chilled ceiling system. However, it should also be noted, that it does become warmer in the scenario without mechanical cooling. Thus, the requirements to the thermal environment must be less strict than in normal air-conditioned buildings, if such a solution is chosen. In the Aget building an external solar shading system is combined with night cooling, ceiling fans, free cooling via ventilation air and indirect evaporative cooling. In total 11% of the energy demand is saved in this way (from 347 kwh/m² to 311 kwh/m²). Of this, the largest saving is on mechanical cooling (43% saving). Both the Danfoss scenarios are not profitable due to the negative present value arising from the very high costs of the openable windows. In contrast to this, all the Postbank Berlin scenarios and the Aget scenario are profitable. This mainly reflects the difference in the cooling demand in the three reference buildings. In the Postbank Berlin building the reference cooling demand is high due to the large window area and the low cooling set-points. In the Aget building the high reference cooling demand is due to the high internal heat gains, mainly from the lighting system, and the warm Mediterranean climate. The low capital costs necessary to complete the retrofitting, also have an important influence on the profitability of the Aget scenario. 6.3 Electric lighting scenario For the Danfoss building two lighting scenarios are examined. Scenario 1 involves the following three measures: Use of HF-ballasts (High Frequency ballasts) in all areas plus combined occupancy and daylight responsive control of general lighting in office areas. Scenario 2 involves only HF-ballasts and daylight control. From table 4 it can be seen, that the two scenarios results in the same small 1% reduction in the total energy demand from 331 kwh/m² to 328 kwh/m² (44% saving on lighting demand and 2% increase on heating demand). This means that the most cost effective scenario are the one, which combines HF-ballasts and occupancy control (lowest costs). The savings are the same in the two scenarios, simply because the daylight responsive control method are so effective, that the lighting will be turned off during most of the day, thus an occupancy control system will have little extra effect. The total energy savings are also

8 small due to the fact, that a saving on internal lighting will result in an increase in the energy demand for heating. As a consequence of the small savings, the present value are in both cases negative, thus the investments must be considered poor from a pure economical point of view. The Postbank Berlin lighting scenario involves replacement of the existing windowpanes with more transparent windowpanes and improvement of the general lighting system by use of effective HF-ballasts and daylight responsive control. In this way, the total energy demand is reduced from 273 kwh/m² to 241 kwh/m² (12%), mainly due to the reduction in lighting demand (55%). Actually the cooling demand is increased (19%), due to the more solar gains entering the building because of the more transparent windowpanes. This is also the reason why, the heating demand also is reduced (12%). As consequence of the mixed result where energy demands are both reduced and increased, the present value are negative, thus the investments is not profitable. The Aget lighting scenario involves improvement of the general lighting system by reducing the installed power, using more effective lamps, reflectors and ballasts (HF) and by use of task lighting, daylight responsive control and timer control of the general lighting. In this way, the total energy demand is reduced from 347 kwh/m² to 263 kwh/m² (24%), mainly due to the reduction in lighting demand (75%), but also the cooling demand is reduced (16%). As with the Danfoss building the heating demand is increased (8%). Due to the very high lighting demand in the existing building, the present value is positive, thus the investment is profitable. 6.4 HVAC scenario In the Danfoss building this scenario involves reduced air rate and running time of the ventilation system during winter, use of new effective fan systems and use of new openable windows, which allow for user controlled pure natural ventilation during summer. As a consequence, the total annual energy demand is reduced from 331 kwh/m² to 214 kwh/m² (35%), divided on a 36% reduction on the heating demand, a 99% reduction on the cooling demand and a 83% reduction on the ventilation demand. Mechanical cooling is almost completely avoided, because the mechanical ventilation system is shut down during the summer. The present value of the investment is positive, thus the investment is profitable. In the Postbank Berlin building the HVAC scenario involves reduced ventilation rates summer and winter, reduced running time of the ventilation, use of a BMS controlled night ventilation strategy and use of new effective fans in the ventilation system. As a consequence, the total annual energy demand is reduced from 273 kwh/m² to 179 kwh/m² (34%), divided on a 32% reduction on the heating demand, a 39% reduction on the cooling demand and a 76% reduction on the ventilation demand. The present value of the investment is positive, thus the investment is profitable. In the Aget building this scenario includes: Use of a BMS to control the HVAC system, decreased heating set-point, new boiler system and heat recovery from ventilation air, boiler flue gases and condenser coil. The total energy demand is reduced from 347 kwh/m² to 214 kwh/m² (38%) divided on a 30% reduction on the cooling demand and a 70% reduction on the heating demand. The present value show the highest positive value of all, meaning that the investment is the most profitable of the scenarios and packages examined for the Aget building. 6.5 Packages The packages involve the most promising of the measures from the scenarios. For the Danfoss building this is: Improved insulation standard of envelope (opaque elements as well as windows). Reduced infiltration rate. Heat recovery of ventilation air. Use of an effective BMS controlled ventilation strategy with reduced running time during cool periods and night ventilation during warm periods. Use of new effective fans in the ventilation system. Reduced ventilation rate during summer and winter. Use of natural ventilation to assist mechanical ventilation during summer. Reduced heating set-point during night and weekend. Use of an effective BMS controlled external solar shading system. Automatic control of general lighting in response to daylight levels. No use of mechanical cooling (system demolished). Consequently the total energy demand are reduced from 347 kwh/m² to 95 kwh/m² (71%) in the Danfoss building. The reductions are divided on cooling demand (100%), heating demand (82%), ventilation demand (56%) and lighting demand (29%). The Postbank Berlin package involves measures similar to the ones in the Danfoss package: Improved insulation standard of envelope (opaque elements as well as windows). Reduced infiltration rate. Heat recovery of ventilation air. Use of an effective BMS controlled ventilation strategy with reduced running time during cool periods and night ventilation during warm periods. Use of new effective fans in the ventilation system. Reduced ventilation rate during summer and winter. Reduced heating set-point during the day.

9 Automatic control of general lighting in response to daylight levels. Use of effective HF-ballasts in the office area. As a consequence the total energy demand are reduced from 273 kwh/m² to 72 kwh/m² (74%) in the Postbank Berlin building. The reductions are divided on cooling demand (3%), heating demand (92%), ventilation demand (67%) and lighting demand (48%). For the Aget building all the measures from the scenarios described above are included. This results in a reduction of the total annual energy demand from 347 kwh/m² to 124 kwh/m² (64%). The reduction is divided on lighting demand (79%), cooling demand (48%) and heating demand (63%). The three packages result in a positive present value varying from 77 Euro/m² for the Danfoss building, over 138 Euro/m² for the Aget building to 341 Euro/m² for the Postbank Berlin building. All the three packages are therefore profitable and worth investing in. 7. CONCLUSION It is difficult to venture into a detailed comparison of the different results obtained in the design and evaluation activity in the OFFICE project. There are several reasons for this: The buildings are all different, in different physical conditions, and placed in different contexts. The needs for refurbishment, and the effectiveness of refurbishment, both in terms of reductions in energy demand and improvements in comfort, and in terms of cost, therefore differ from case to case. For instance the cost of a given measure, such as replacement of a window, differs enormously from country to country, even though it appears that the window specified in the different cases is the same. The difference may be due to differences in market prices and labor costs. The cost issue is clearly the most difficult one to deal with across cases. Another reason for this is, of course, that there are significant differences between the price of energy in the various countries. The cost effectiveness of a given measure may therefore differ from country to country, even if the price of the measure is the same in these countries. Another issue is the fact, that the climates at the locations of the different case study buildings all are different. However, based on the scenarios and packages examined some overall conclusions can be made. The following conclusions therefore refers to all the case study buildings, and not just the Danish, the German and the Greek buildings: Available energy efficient and renewable energy technologies can contribute to a reduction in the energy demand in high energy use office buildings. The choice of technologies to be considered has to be based on the very specific energy characteristics of a given building. The combination of technologies must be carefully selected in order to avoid use of multiple measures, that produces the same results and therefore have no additional impact, but to increase the cost of the retrofitting action. In warm climates, where the cooling loads are high and where these loads are not completely due to internal gains, passive-cooling techniques may result in significant reductions in energy demand for cooling. In cold climates, where the heating loads in existing buildings are high, envelope improvements and the use of solar gains may result in significant reductions in energy demand for heating. In all climates, the potential reductions in lighting energy demand are limited. For buildings with initially very high lighting energy use, the reductions can be substantial, however. When high energy demand primarily is due to operational problems, as for example poor control of ventilation, or incorrect set point temperatures, the use of advanced control systems may reduce energy demands significantly. 8. THE EU OFFICE PROJECT The outcome of the OFFICE project, including results and analysis from the Design Evaluation Group, are described in the project reports. The EU OFFICE project was coordinated by University of Athens. The Design and Evaluation Group was coordinated by The Norwegian University for Science and Technology and Esbensen Consulting Engineers, Denmark.