Assessment of the sustainability of flexible building : the improved factor method : service life prediction of buildings in the Netherlands, applied to life cycle assessment

H. van Nunen

Research output: ThesisPhd Thesis 2 (Research NOT TU/e / Graduation TU/e)


The building sector is not well-known for its innovative character. Once in a while a particular field of expertise receives an impulse. In the period 1999-2005 such an impulse was given to the Industrial, Flexible and Deconstructable (IFD) building programme, which was funded by the Dutch national government. The aim of this programme was to stimulate innovation in the building sector. Buildings that contributed to one or more of these aspects were liable for subsidy. Eindhoven University of Technology participated in one of these projects, called ‘IFD-today’. IFD-today is an innovative apartment building system with industrial, flexible and deconstructable features. It consists of a steel frame and an extremely flexible floor concept. The dimensions are large (7.2m x 11.2m), and no extra support columns are needed. The partition walls can be placed anywhere, which allows for homes in different sizes. The concept was developed jointly by a housing association, a contractor and an installer. The university’s main reason for participating was the opportunity to carry out research on the development of the building, as well as the techniques that were used. A flexible building can be adapted to the wishes of the occupant. Therefore none of the (living) functions in ‘IFD-today’ is bound to specific locations in the layout, not even the toilet. Because of this flexibility, a building can be adapted more easily than a traditional building. This poses the main research question: To what extent is the environmental burden of the IFD-today apartment building system lower than the environmental burden of a traditional building? To make this visible the environmental burden needs to be quantified. The calculation is an essential part of this visualisation. Life Cycle Assessment Environmental burden is measured according to a Life Cycle Assessment, or LCA. This calculation method is based on all the materials and processes needed for a product during its entire life cycle. It is often called a cradle to grave approach. For each material or process (for example excavation or transport), the emissions into the environment are known. By using a computer program such as SimaPro, it is possible to convert the emissions into environmental effects. These environmental effects can be assessed according to their impact on the environment. There are several methods for LCA available, however all methods need solid input. Input proves to be difficult when looking at a (flexible) building. First of all, a building has a long lifespan, therefore the necessary maintenance and replacement is needed during its use. The second reason why it is difficult, is ascertaining the service life of a product. And when the service life is known, it is only a reference service life, i.e. an average. The reference service life will not always be met in a flexible building. For instance, due to its flexibility, replacements will occur more often. A service life that is suitable for (flexible) buildings is therefore needed. Only then can the proper amount of materials needed throughout the lifespan be known and an LCA be performed. A building consists not only of the initial construction, but the improvements throughout the years (alterations) also form a necessary part of the life of a building. These cycles are inextricably connected with the building. The various alterations of a building, whether it is conservation, renovation or transformation, form the building over a period of time. These alterations must also be incorporated in the LCA. A further problem arises. Before an LCA can be conducted, a so-called functional unit, on which the alterations and replacements are based, needs to be described. The requirements of the product are described in this functional unit. For example, the building’s function (e.g. a family dwelling), how many people it houses (e.g. three persons), and the insulation level (e.g. Rc > 3.0 m²K/W), are aspects that can appear in a functional unit. In addition to these three examples, the length of time the building will be used (lifespan) is also important. This is a difficult question to answer, as the lifespan of a building is not known beforehand. Research has shown that the average lifespan of a building in the Netherlands is 120 years. This period is used in the functional unit. Service Life It is possible to predict when a product can no longer fulfil its technical function in several ways, i.e. long-term testing, accelerated testing, and by means of calculation. These are all based on the technical service life. Looking at the way a product will fail this can occur in three different ways, i.e. functional, economic and technical. These days, it is no longer just the technical service life that indicates replacement, but increasingly economic and in particular, functional reasons that indicate replacement. During this research the Factor Method came to the fore. This method, defined in the ISO 15686 series, presents a way of using a reference service life (RSL) combined with seven known factors: (A) quality of components, (B) design level, (C) level of work execution, (D) indoor environment, (E) outdoor environment, (F) in-use conditions, and (G) the maintenance level. The RSL can be transformed into an estimated service life (ESL) using the effects of the factors. The ESL can be adjusted for specific circumstances, by giving a higher (better), or lower (lesser) value to the factor. The default value of the factors is 1.0, therefore the RSL and ESL are equal if no other effects occur. The Factor Method provides a method that is relatively simple, but offers more detailed information about service life compared to the average RSL. The Factor Method is described by the formula ESL = RSL * A * B * C * D * E * F * G The Factor Method is quite new. In 2000 the first ISO standard (15686-1) was published and the last one dates from 2008 (15686-9). Up to now, there is not much expertise in the field, and research is still ongoing to improve the application of this method. The method leaves room for improvement. In this research, three major improvements are added to the existing method. The Improved Factor Method The Factor Method in its current form is mainly concerned at technical service life. There are more reasons for obsolescence possible. Next to that the Factor Method has a fixed value, but in practice variations occur. Finally it can be questioned whether all the factors are of equal weight. These three problems offer an opportunity for improvements of the existing Factor Method. The first improvement is the addition of two factors. It is stated that technical requirements are no longer the only reason for replacement, but that economic and functional requirements need to be incorporated as well. Looking at the indicators for replacement, two factors were added. The first one is called ‘Trends’ (T). This factor is used to adjust the reference service life according to the choices people make, based on how a product looks (image), or how a space is used (usage). This factor is especially important when flexibility is an issue. The second added factor is called ‘Related components’ (R), and is used to take replacements into account that are not necessarily based on technical deterioration, but because other materials connected to the one under review are replaced, (i.e. the window-pane is replaced at the same time when the window frame needs replacement). The second improvement is the addition of probability to the factors. Each factor is awarded a suitable statistical probability. That way the outcome is no longer based on a fixed value but it now depends on a statistical distribution. Nine separate distributions are used, and each factor therefore has the most fitting distribution. The third improvement is the application of weighing to the factors. Weighing is a possibility that is not used at present. However, it is possible that some factors have a larger influence than others do. A set of weighing factors is therefore added to the method. During the data collection for the weighing factors, the possibility of excluding one or more factors was also examined. In the end, all nine factors (seven original and two new factors) were provided with a weighing factor. With these three improvements, the Factor Method is transformed in the next phase, the Improved Factor Method. With the Improved Factor Method, the Improved Estimated Service Life (IESL) can be calculated. This is a service life that closely resembles the actual situation, because it is based on nine different influences which compensate the RSL. In order to draw a comparison between a traditional building and a flexible building, there is still one effect that is not accounted for. The functional obsolescence is partly covered by the factor Trends, but there are also changes based on how people use the spaces and rooms in a building. Scenarios are used to cover this as well. Adding scenarios Scenarios need to show the use of tomorrow. For the building and the inevitable alterations the dimensions are used as an indicator. The basis of the scenarios is the concept that the requirements of dimensions of a room will change over time, but eventually will meet a maximum floor area. This maximum floor area is called the saturation area. The saturation areas for living room, kitchen, bathroom, and bedrooms were set using an expert panel. Looking back in time and combining the construction history with the expected growth in the future, provides a scenario for the expected development of the dimensions of the rooms. There are three different levels (low cost, affordable, expensive), to describe the differences in luxury of the buildings. When the actual square footage is below the required square footage in the scenario, an alteration to that room is needed, (i.e. a bathroom that becomes too small can be moved to a spare bedroom). This way, using the different minimum dimension, the lterations that are needed to keep the house available for the same target group for 120 years become clear. These alterations often coincide with natural moments (end of the IESL and the need for more space), but sometimes early replacements are needed, not because of the materials, but because of the need for space. The Improved Factor Method combined with the scenarios, provides a reliable service life prediction that generates the amount of materials needed for a Life Cycle Assessment. Now the assessment of a traditional building and a flexible building (the main research question) can begin. Five projects from the IFD-program are used to make the comparison. These projects all have a different level of flexibility. Flexibility is defined as consisting of five aspects, i.e. function level, floor area, appearance, layout and finishes. Using the Improved Factor Method with scenarios, the environmental burden of these projects are all calculated together with a traditional reference project. For each project, the total quantity of materials needed over time is determined with the Improved Factor Method with scenarios, and subsequently the environmental burden is calculated in SimaPro. The results are calculated in Ecopoints, using the Eco-Indicator 99 method. The total number of Ecopoints is divided by the weighed square footage over 120 years, and the outcome therefore consists of Ecopoints per square metre. In this way, the demonstration projects, selected out of the IFD-program can be compared to each other. The results show that there is a relationship between environmental burden and flexibility: the more flexible a building is, the lower is the environmental burden. However, there are some exceptions to this relationship. Results Eventually a model that is able to predict the service life of a component more accurate is developed. With this model the input of LCA can be more accurate. When the projects were calculated, it was also possible to make a distinction between the build-phase (29%), the use-phase (50%), and the demolition-phase (21%), with respect to the environmental burden. The amount of waste generated by a building is more than just the 21% of the demolition phase. The 50% environmental burden in the use-phase can be divided into 36% building and 14% demolition. This means that 35% of the Ecopoints are caused by waste. The analysis of the overall calculations of the projects gives rise to a number of observations. When the current methods are set at 100%, the Improved Factor Method with scenarios shows differences ranging from 9% to 45% when compared to the current methods. The project with a 45% gap is the one regarding traditional building. More accurate calculations therefore show more replacements and more materials than the current methods do, causing a 45% gap. With the flexible projects, this gap varies from 9 to 29% . This speaks for the assumption that flexible buildings cause a lower environmental burden than traditional buildings. Besides providing a comparison, the Improved Factor Method can also be used for the optimisation of a single project. Looking for materials with the right service life, or choosing materials with a different environmental profile can reduce the environmental burden. Three hypotheses were formed in this research. The first one is that flexible building causes a lower environmental burden than the traditional way of building. This hypothesis is only partly true. There is a relationship between flexibility and the environment, but this relationship does not always happen because some inconsistencies occur. But in general, this hypothesis is true. The second hypothesis is that the reference service life of a component (RSL) has a limited connection with everyday practice. Based on the various calculations applied in this research, this hypothesis is true. The differences that occur between RSL and IESL are + / - 20% on average, but sometimes differences of 30-40% occur. The third hypothesis is that the cycles of building adaptations define the environmental building. The calculations based on the Improved Factor Method with scenarios, proves that this hypothesis is true. Of the environmental burden 50% is caused in the use phase. Discussion The Improved Factor Method is a step forward in service life prediction. However, the method is not optimal as yet. The main goal of this research was to establish a working model that could compensate for different influences, and ultimately would be able to calculate the environmental burden of a flexible building. Some choices were made that require more profound research. Perhaps the nine factors can be clustered into groups. In that way, fewer assessments will be needed, which will make the method easier to use. Besides that, the weighing factors were established as one set of generic factors. It was acknowledged that several weighing sets (for different functions) would be more appropriate. In order to keep the model simple, this was not done at that time. In the last step, scenarios were used to point out the times when alterations were carried out. Although this is a good guideline, it is only based on several hundred buildings, a small number when compared to the entire housing stock of 7 million houses. Service life has an influence on the environmental burden. It is therefore important that calculation models that try to quantify the environmental burden have the right starting point. A reference service life is not sufficient on its own. Several circumstances have an effect on the reference service life. These circumstances alone can cause up to a 10 percent spread in the service life. Adding more factors, probability, weighing and the use of scenarios makes it even clearer that service life is important. It shows a maximum difference of over 40 percent (current method compared to Improved Factor Method with scenarios) compared to the current situation. Greater insight into calculation with service life is gained with the Improved Factor Method, whether it is used for environmental calculations such as LCA, or for maintenance and cost calculations such as LCC. Besides the development of the method with all its steps, there are also some general conclusions. IFD building does prove its worth over time, at least where the environment is concerned. Furthermore, from the demonstration projects it can be deduced that initial building is only responsible for 30% of the environmental burden. The use-phase is accountable for 50%. Therefore concentrating on the first phase only is not enough. It also is an indication that the existing housing stock is important when sustainable building is regarded. It is also indicated that the total environmental burden of a building, energy consumption included, is divided over 45% energy and 55% materials. Where sustainable building is concerned, the focus is now mainly aimed at the energy side. The energy use of buildings can be reduced, but the energy consumption of appliances will still be large. Therefore reducing the environmental burden of materials will also be necessary, if the goal is to reduce the total environmental burden. Finally, it cannot be emphasised enough that a
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Built Environment
  • Hendriks, Nico, Promotor
  • Westra, Jan, Promotor
  • Erkelens, Peter, Copromotor
Award date21 Oct 2010
Place of PublicationBoxtel
Print ISBNs978-94-6104-014-5
Publication statusPublished - 2010

Bibliographical note

Proefschrift Technische Universiteit Eindhoven


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