Implications

4.1.1 Theoretical implications

In introducing the need for a paradigm change, Kohler and Hassler (2002) argued that until then, building stocks had not been researched systematically. The lack of systematicness is also evident when it comes to the research on the Finnish building stock. All Kohler and Hassler's (2002) observations about the state of research on building stocks apply to the Finnish context: data is better on housing; NRB are largely neglected; research is sectorized, with narrow objectives; and the results are often not generalizable. Unlike many countries, Finland, however, has relatively good basic data about the composition of the stock.

Taking advantage of this data as well as newly collected research material, the current dissertation has introduced the new paradigm to the research of the existing stock in Finland. The findings demonstrate the advantages of using large datasets that lead into generalizable results, contrary to isolated case studies. Although building stock research starts off from a down perspective, the dissertation shows that both top-down and bottom-up approaches can result in generalizable results. In fact, since the availability of all-encompassing (top-down) data is limited, both approaches are equally necessary.

The key objective in building stock research is supporting sustainable management and long-term preservation of the built environment (Kohler, Steadman & Hassler, 2009). This requires understanding the dynamics of the stock, that is, drivers related to the replacement of buildings. The lack of data on buildings at their end-of-life phase is

even more critical than that of other parts of the stock. (Thomsen, Schultmann & Kohler, 2011). Therefore, most research on this topic has relied on theorizing and models.

This dissertation, on the other hand, has employed the Finnish BDR data to investigate obsolete, that is, demolished and problematically vacant, parts of stocks. Many of the findings from the research support current theories and some of them can also help to validate or develop existing stock models. The research, for instance, illustrates that assumptions about the shorter lives of NRB are justified, and that the mortality in the building stock is dynamic, not static or variable. Thus, NRB seem indeed to need different approaches than RB, as suggested by Sartori et al. (2008), and any approaches employing assumptions relying especially on static mortality appear to be fundamentally flawed and should preferably be relinquished.

Moreover, this dissertation has been amongst the first to discuss the complex relationship between demolition and vacancy, and it has done so based on real data.

Whereas vacancies are monitored and investigated intensively in housing market research, their role is currently largely neglected in the study of building stock dynamics.

The findings on the location, composition and dynamics of the obsolete parts of stock can act as the basis for assessing the magnitude of material deposits and for the future modelling of metabolic behaviour. As Meinander and Mroueh (2012: 19) have observed, there is, however, a lack of data at the unit level on the material composition of the stock that currently prevents these kinds of analyses from taking place. This dissertation has also started to bridge the gap by investigating the component composition of one exemplary cohort. The approach did not only result in an assessment of the cohort's raw material content but elaborated on the types of structures and building parts, as follows from EU's targets to move up on the waste hierarchy and to refine recycling and reuse of physical resources. The same method can, and should, also be used for studying other cohorts, in order to properly quantify the potentials of the existing stock as a deposit of spaces and components.

A focal aspect in shifting to more sustainable building stock management is the overall deceleration of urban metabolisms, that is, decoupling the service provision of buildings from the use of materials (Pauliuk & Müller, 2014). Therefore, already existing buildings should not only be seen as deposits of materials or components, but as reserves of possibly usable space (Kohler & Hassler, 2002; Thomsen & van der Flier, 2011). Using the exemplary cohort, this dissertation has demonstrated how the spatial arrangements in a cohort can be investigated and generalized, providing the basis for evaluating the cohort's adaptation and modification potential. The introduced method is appropriate for researching other cohorts, too, although due to their different nature, NRB cohorts may also require other graph theoretical approaches.

4.1.2 Practical implications

As the research presented herein represents basic research on the building stock, its practical implications are not as immediate as its theoretical ones. Since the objective of building stock research is, eventually, to support sustainable stock management (Kohler, Steadman & Hassler, 2009), the practical implications of the current study are also mostly related to the insights it can provide for administration and decision-making.

Kohler, Steadman and Hassler (2009) remind that public policy-making should base on evidence. Systematic analyses of building and housing stocks and their state of usage do not currently underlie national building stock policies in Finland, neither do they inform Finnish municipalities' zoning and planning decisions. Thus, public decision-making would benefit from understanding the magnitude, location and qualities of reserves in the existing, vacant and demolished parts of both national and local stocks and acknowledging what could be done with the obsolete parts of the stock, were they reconsolidated. With two-thirds of Finnish municipalities shrinking in terms of inhabitants, many of them would benefit from exchanging the growth paradigm into a more stock-centred one. As Rajaniemi (2006) has demonstrated, the growth paradigm can have detrimental effects for the quality of their built environments.

Continuing new construction vigorously when extensive amounts of vacant spaces are available, not only in declining areas but also in growth centres in certain building types (such as offices) is not just illogical but also harmful from the resource efficiency perspective. Were policy-makers and planners aware of the youngness of demolished buildings' age distributions and the extent of vacancy in Finland, they could instead choose to work towards encouraging buildings' continued use and adaptive reuse. The findings of the current study imply, for instance, that the need to increase floor area may result in demolition decisions. This increase could, however, also be achieved through building extensions and/or infill development, if policies did not exacerbate demolition, as Thomsen, Schultmann and Kohler (2011) have argued. Moreover, the shorter lives of NRB and their replacement with RB suggest that adaptive reuse as RB could be a viable option for extending the lives of NRB. This strategy has also been proposed by Bradley and Kohler (2007), who have reasoned that NRB are not structurally inferior to RB. These prospects could enlarge business opportunities for construction enterprises specializing in renovation of existing buildings.

Besides construction companies, also building owners could be expected to be interested in insights that the current research offers for the development of buildings.

These kinds of practical implications of the dissertation are mostly related to the exemplary cohort that was investigated in more detail. Even prior to this research, there

were many studies regarding the renovation of the examined cohort that relied on 'typical' buildings or flats, although the selection of these acclaimedly representative units was based on intuition rather than research. The results on the spatial qualities of the studied cohort do not only provide a basis for developing mass-customizable renovation and home modification concepts but also validate the choices made in prior similar studies and increase their usefulness retroactively.

The obsolete parts of building stocks withhold significant potential, not only in the physical sense but also in terms of business. If these buildings continue to be ignored, chances are that not only their resources but also these opportunities will be wasted.

So far, the rate of demolition has been moderate in Finland. Given the extents of vacancy and underutilization, however, an unforeseeable number of these buildings might face demolition in future, creating either unprecedented amounts of demolition waste or a major input of materials and components into the construction industry.

Therefore, the business opportunities in the demolition, deconstruction, recycling and reuse of the materials from the existing stock should be acknowledged better.