The environmental impact of alternative structures for the XX-office building in Delft, Netherlands, each as a result of a different design approach

Transcription

1 September 2004 Page 1 of 6 The environmental impact of alternative s for the XX-office building in Delft, Netherlands, each as a result of a different design approach Ir. Rijk Blok 1 and prof. Ir. Frans van Herwijnen 1 1 TU/e, University of Technology, Eindhoven, Netherlands ABSTRACT: This paper compares the environmental impact of two alternative building s for the XX-office in Delft, Netherlands using different life scenarios and different disposal scenarios. Conference Topic: 5 s, building techniques and sustainability Keywords: Life cycle design, LC(I)A, Building, Sustainability, design strategy INTRODUCTION The actual build Structure of the XX-office building has been the result of a new design approach of balancing the Technical Service Life of the building and its with the estimated and foreseen (shorter) Functional Working Life This poses a problem in evaluating (expected) environmental impact of buildings at the design stage. For building s this is even more so because the is usually the longest lasting part of the building. Important factors in the service life of building s are: The s technical qualities: a sufficient level of resistance during its life time (durability) with regard to ultimate limit states. This determines the Technical Service Life (TSL) of building s. Factors such as deterioration and degradation of building materials influence the s technical qualities. Figure 1: XX-office Building Life time In sustainable building the main goal is to reduce the negative impact of the building on the environment. The resulting impact per time-unit depends for a large degree on how long the building and its can meet the minimum requirements before it becomes redundant and before it is abolished. The environmental impact of the extraction of materials, the fabrication, construction and demolition of a stays the same, independent of how long the is used. When the much smaller environmental impact of maintenance and repair is disregarded, the impact per time-unit of use is inversely proportional to the service life of the. The s functional qualities: providing a sufficient level of space and bearing capacity as required by its users: This determines the Functional Working Life (FWL) of building s. Factors as free storey height, maximum floor load, flexibility for possible changes in use and changes to building services and installations etc. influence the functional qualities of s. The s economical qualities: providing a sufficient level of financial returns as required by its owners during its lifetime. This determines the Economic Service Life (ESL). Factors like initial construction cost, (projected) cost for maintenance and repair, returns from rent, cost for refurbishment or demolition influence the economic quality of building s. The technical, functional and economical aspects mentioned above (with their mutual interactions) play an important role in the decision process regarding the ending of the service life of a building. Social and cultural factors, for example historic value, can sometimes also play a significant role.

2 September 2004 Page 2 of 6 To improve on sustainability, in particular of future buildings, improvement on design strategies in relation to the future life of building s is needed: Integrated Life Cycle Design. For the Life Cycle Impact Assessment of the XXoffice Building the effects of different life scenarios and different disposal scenarios were evaluated. Minimizing negative environmental impact by designing a building with a TSL equivalent to the expected FWL of the building was the strategy that was adopted with the design of the XX-office building. Demands in housing of organisations can change very fast. The Functional Working Life becomes more often the governing factor in the lifespan of a building. For this reason, the of the XX-office building in Delft, Netherlands has been designed for a limited anticipated FWL equal to the TSL of (only) 20 years. To achieve this the of the XX-office has been build in reusable and recyclable, untreated, mainly wooden (Swedlam) materials and components, after considering also a number of alternative options. 2 The Structure of the XX-office building Figure 2: XX-office interior, structural lay-out This would be totally demountable and suitable for re-use. Out of cost considerations a traditional non-demountable concrete foundation with concrete piles and beams was used instead. After the 20-year period the concrete at least can be re-used as crushed-concrete granulate. The spatial plan of the XX-office shows two rectangular floors of 15 m x 66 m (3 bays of 5m in transversal and 11 bays of 6 m in longitudinal direction). The 6m column to column distance is spanned by primary beams: Timber Swedlam beam sections 184,5 x 300 mm subtended by M52 Rodan anchor tie rods. The secondary beams, with the same section dimensions, span the 5m distance at 2m centre to centre. The span of the timber floor joist is thus limited to 2m. The is supported by square wooden columns 300 x 300 mm. The joints are constructed with pin fasteners and steel plates. The first floor construction consists of timber floor joists (59 x 146 mm, 417 mm centre to centre) with a fire-resistant board Antivlam (thickness 22 mm) glued to the underside of the joists, to obtain a composite panel. The space between the joists is filled with sand on a foil. The sand provides for an important contribution to the acoustic insulation. The space also accommodates service ducts. On top the cement fibre-reinforced panels (24 mm thickness) are supported on the timber joists using an elastic intermediate layer. The roof uses the same structural lay-out as the first floor, however with reduced sectional dimensions of the beams due to the difference in life load (Roof: 1 kn/m2 / Floor 4 kn/m2 ). The original design was based on a foundation out of steel-tube piles with cathode protection combined with steel integrated-section beams between which the concrete prestressed hollow-core slabs spanned. Figure 3: First floor build-up XX-office Structure For more specific information on the XX-office : See ref. [1] 3 The Reference Structure In order to evaluate the XX-office Structure an alternative Reference Structure for the building has been designed. Figure 4: Impression of Reference Structure. For this Reference Structure the minimum Design Life of 50 years was used. The Reference Structure uses the same building dimensions. The has

3 September 2004 Page 3 of 6 been designed as a braced steel construction with prefabricated pre-stressed concrete hollow-core floor slabs, thick 200 mm. The 15 m width in the transverse direction was altered to 2 bays of 7,5 m for the Reference Structure, because of the greater possible span of the prefabricated floor slabs. The steel beams have been designed as integrated steel (IFB) profiles. The columns on the ground floor are steel sections HE 200A, on the first floor steel sections HE 140A. The bracing system has been chosen similar to the XX-office. The steel was finished with a factory applied paintcoating. Due to the integration of the steel beams in the height of the floor no extra measurements were needed to meet the required fire resistance of 30 minutes by the Dutch codes. (The ground floor and foundation of the Reference Structure was kept identical to the XX-office Structure and were therefore disregarded in the performed LC(I)A calculations.) 4 LC(I)A calculations 4.1 Approach of the Life Cycle Impact Analyses The used LCIA is based on the method developed by the Centre of Environmental Science Leiden (ref. [2]) It clearly identifies a number of different steps. To analyse the materials and the processes involved for both s the computer program Simapro (see [3]) has been used. The negative impact or damage assessment of the used materials and processes has been quantified in different categories using the Eco-indicator 99. The Eco-indicator 99 is a damage oriented method for LCIA. It uses the following classification of categories: Damage to Human health: carcinogens respiratory (in-)organics climate change radiation ozone layer Damage to Ecosystem quality: ecotoxicity acidification/ eutrophication land use Resources: minerals, fossil fuels Tabel 1: Classification Impact categories Ecoindicator 99 The Eco-indicator 99 is an (expert-) interpretation of the impact-effects of certain materials and processes on the environment, partly based on opinions. Although it might not be suitable for exact scientific quantification of all involved effects, it does facilitate the comparisons. The used method follows ISOstandard as close as is in practise possible. Because the absolute numbers of the environmental impact were not the main goal, but the relative comparisons of different s and their life cycles, this method was regarded as best suitable. Finally, to compare the damage and impact effects, a normalisation has been used. The impact has been calculated as a single score in Points. One thousand Points equals the total negative impact on the environment of an average West-European habitant in the reference year (1990). 4.2 The adopted different life and disposal scenarios Comparing 50 years of functional use To compare the environmental effects of a deliberately designed with a TSL much shorter than 50 years, with a that has an expected TSL longer than 50 years, different life scenarios were adopted, spanning a period of functional use of 50 years. Life scenarios XX-office A B C D Reference XX-office Reference Functional Working Life Disposal scenario High degree of Low degree of Functional Working Life Disposal scenario High degree of High degree of Low degree of Low degree of Figure 5: Four life and disposal scenarios for the different s over a fifty year period. To allow for what was regarded as a more realistic scenario and to ease comparison with the reference a stretched life -scenario for The XX-office of years was used instead of the originally intended life of 20 years. The Technical Service life of XX-office is not unlikely to stretch beyond the intended minimum of 20 years. This decision will be evaluated below. Thus a number of different Life-Scenarios (A to D) have been compared. The four most significant life scenarios are shown above (fig. 5). (for two additional life scenarios is referred to ref [4]) Figure 5 shows that due to the limited foreseen Technical Service Life and limited Functional Working Life it is assumed that for the time span of fifty years two XX-offices s are needed. (Life scenario A and C). The impact of two XX-offices s have thus been compared with the impact of one Reference Structure. To account for the effects of different ways of disposal, basically two different Disposal Scenarios were assumed and calculated as described hereafter

4 September 2004 Page 4 of The disposal scenarios High degree of material : Assumed is a disposal scenario were elements are fully separated and disassembled. Where possible as much as 90% high-level- of materials and only 10 % dumping and / or incineration, depending on the materials, has been calculated. Low degree of material : Assumed is a disposal scenario of separation and disassembling (demolishing) with, depending on the materials, only 10% re-use and up to 90% dumping and / or incineration. A realistic approach more or less representative of the current Dutch situation has been chosen. This means that where possible and re-use at material level was assumed anyway. Dumping for landfill was minimised. The main differences with the High degree of material were the dumping, instead of assumed reuse of crushed concrete as new aggregate materials and the incineration in stead of re-use of wood. 5 Results and comparisons 5.1 Results of the Scenarios A to D on Human Health, Ecosystem Quality and Resources (Because of the high amount of resulting output only a limited outline of the most striking results will be discussed.) Pts Figure 6: Single score impact results of the different life scenarios A to D. Although the shorter assumed FWL and TSL of the XX-office requires the use of two s over a 50 year period, these scenarios (A and C) still show lower impact figures (a total of single score, Points for scenario A and points for scenario C). 5.2 XX or XXV ,5 1747, ,5 If instead of the used twenty-five years the originally intended FWL of twenty years is used the figures change. It would mean that an extra XX-office should have to be build to span the fifty years period. To compare the environmental impact Life sc. A Life sc. B Life sc. C Life sc. D Human Health Ecosystem Quality Resources per year of use, it would mean that an avarage of 2,5 s of XX-office are needed for a fifty year period. This would result in a single score impact figure of 2,5/2 x = points for the high degree of material. This is approximately the same as life scenario B: points. Using twenty years with the low degree of material, the XX-office building would have a slightly bigger impact (2,5/2 x =.004 points) than scenario D (D: points). (Remark: Life scenario A and C can have other advantages, for example it can be decided to optimise the configuration of the new according to new demands and/or make use of new available technologies.) Taken into account that two or more s are needed, it is clear that with regard to the impact figures the XX-office has a good score compared to the Reference Structure. The design approach shows, at least for the High degree of material to be effective. On the other hand it becomes very clear that the actual realized duration of the real Functional Working Life of the in the future will be decisive. 5.3 Comparing Life Scenarios Comparing the life scenarios it shows that the XXoffice has a much better performance than the Reference Structure in the field of Human Health, see fig. 7 below carc. resp org resp inorg climate ch. radiation Life scenario A: 2x XX-office High level Life scenario B: Ref. struct. High level Life scenario C: 2x XX-office Low level Life scenario D: Ref. struct. Low level Figure 7: Weighed contribution to Human Health, scenarios A to D. The effects of respiratory inorganics make up a large contribution to the relatively high figures on Human Health for the Reference Structure. From the process contribution and also from the specification of airborne dust emission it can be seen that this is mainly caused by the extraction, production etc. of cement-containing materials and elements, such as concrete floors (Ref. 4). ozone l

5 September 2004 Page 5 of 6 This negative cement-effect can also be seen in the XX-office Structure. In the roof- reinforced concrete fibreboards were used, in order to obtain a better performance in heath accumulation and sound absorption. Although the overall performance of the building might have improved by the choice for this roof material (not a subject of this study), it clearly shows a negative effect on the environmental performance of the XX-office Structure (see tabel 2) Process Data Quality Index Unit Life scenario A Total of all processes % 100 ecotox acid/eutr. land use minerals fossil f. Remaining processes % 0,2299 Concrete I BM ++ % 69,56 Cement (Portland) I BM Cement (Portland) I ++ % 19,28 ++ % 9,739 Steel 1 ++ % 1,927 Diesel engine truck -- % 0,3652 PB 1 ++ % 0,3217 Styrene 1 ++ % 0,13 Iron + % -0,1159 Crude coal B + % -0,1835 Sinter, pellet + % -0,5796 PE P + % -0,6689 Tabel 2: Specification of airborne emission Dust (SPM) per process XX-office. With regard to Ecosystem Quality the XX-office Structure shows higher impact figures than the Reference Structure. Reason for this is the large negative impact contribution on Land-use. Reduction in Ecosystem Quality is measured in the loss of biodiversity in a certain area per time-unit. By this definition of Land use, the commonly used methods of mono-culture forestry causes these negative contributions in Ecosystem Quality. The correctness of this outcome and the fairly large contribution of Land use to the single score results might need further investigation. Life Scenario A: 2x XX-office High level Life scenario B: Ref. struct. High level Life scenario C: 2x XX-office Low level Life scenario D: Ref. struct. Low level Figure 8: Weighed contribution to Ecosystem quality and Depletion of resources, scenarios A to D. 5.4 Comparing Disposal Scenarios The results show fairly minor differences between the applied disposal scenarios as described by High Degree of Recycling and Low Degree of Recycling for both the XX-office Structure and the Reference Structure. The High degree of material results in a 10,3% lower environmental impact for the XX office and a 5,3 % for the Reference Structure (single score). The reason for this is the reasonably high level of waste treatment in the Netherlands. It is current practise, to recycle a very large percentage of all the metal components at material level (this was therefore also assumed in the disposal scenario low degree of material ). The timber elements can be recycled at the level of wood pulp and paper production, or can be decomposted. The differences in waste scenario results would possibly have been bigger if the ground floor and foundation (Concrete elements, both the same in the XX-office and the Reference ) were not disregarded. In another study a different disposal scenario for the XX-office was calculated (ref.4) In this study the disposal scenario of incineration of the timber s was compared with re-using the timber. The scenario in which the timber was to be incinerated showed a much bigger environmental impact. The most likely reason for this must be sought in the larger amount of airborne pollutants caused by the incineration, in particular caused by the substances used for the lamination of the timber. 6 CONCLUSION, DISCUSSIONS The design approach used for the XX-office design shows to be successful in minimizing environmental impact effects of the if the life scenario of a Functional Working Life of about twenty five years is assumed. Using these scenarios, the

6 September 2004 Page 6 of 6 used LCIA assessment (Eco-indicator 99) result in considerably lower environmental impact figures compared with the Reference Structure. The impact results depend directly on the length of the assumed Service Life. Improvement on techniques to take into account possible differences in the Lifespan of a is needed. For example a method to evaluate differences in functional quality of a, and therefore a possibly longer expected Functional Working Life, is needed. The used assessment programme indicates that the use of cement containing materials in both types of s give fairly large negative impacts on Human Health (Respiratory Inorganics). In this light the choice in favour of reinforced concreted timberfibre boards in the roof of the XX-office Structure could be re-evaluated. For the XX-office Structure the calculations indicate that the loss on biodiversity, due to monoculture of forestry causes a relatively high negative impact on Ecosystem Quality due to the effects of Land use on the Loss of Bio-diversity. The implications of this effect needs to be looked at further. The overall effects of the different assumed disposal scenarios of the s turn out to be fairly limited in the LC(I)A compared to the influence of the difference in design. It can be seen that decisions taken at the design stage show a larger influence on the environmental impact. This study concentrated on the of the XX-office. LC(I)A of the building as a whole can give different results. ACKNOWLEDGEMENT Authors express their appreciation for the work of Rob Hoekman, graduate student at Eindhoven University of Technology for carrying out the LCIA caculations REFERENCES [1] Herwijnen, F. van: Twintig duurt het langst, Houtblad, vol. 11, No , pp [2] Centre of Environmental Science Leiden (CML), Einsteinweg 2, 2333 CC Leiden. [3] Goedkoop, M. [et al]: The ECO-indicator 99, Methodology report, Amersfoort, 2001 [4] Herwijnen, F. van; Blok R. : LCA comparison of two different building s etc. ILCDES 2003 conference proceedings.