The search for the most eco-efficient strategies
for sustainable housing transformations
G. Klunder
Delft University of Technology, OTB Research Institute for Housing,
Urban and Mobility Studies, the Netherlands
Abstract
Housing transformations are an interesting intervention in post-war housing areas. Two case studies show that housing transformations can fill the gap between consolidation and large-scale demolition. It is often said that this causes less environmental impact. However, not much knowledge on this subject is available yet. Environmentally comparing housing transformations versus new construction not only has to do with environmental impacts during construction, but also with environmental impacts over time. A balance has to be sought between these two kinds of environmental impacts. That is possible by calculating average annual environmental impacts from the year of original construction up to and including discard at the end-of-life of housing transformation or new construction. This is against current opinions of comparing alternatives over the same lifetime. The method will be tested in the next stage of the research.
Keywords: case studies, environmental comparison, environmental impacts, housing stock, housing transformations, intervention, LCA, lifetime, renovation, post-war housing.
1
Introduction
The majority of the housing stock in the European Union was built after the second world war. Quantitative shortages resulted in enormous mass housing production. Nowadays the volume of the housing stock is sufficient. Conversely qualitative shortages are growing. Especially the post-war mass housing does not fulfil current needs and faces the threat of large-scale demolition. Urban renewal is often based on the decision between demolition or consolidation with just
some small interventions. Renovation-based approaches are mostly not considered. Nevertheless, Thomsen and Van der Flier [1] argue that updating the housing stock asks for renovation-based approaches, because of the declining annual housing production. The annual housing production barely exceeds 1% of the total housing stock. Even if this housing production is totally meant to replace demolished houses it takes more than a century to completely replace the housing stock. Finally they state that environmental sustainability and reduction of energy consumption according to the Kyoto treaty plea for renovation-based strategies instead of demolition.
According to Te Velde [2] sustainable urban renewal means that at least the existing stock is dealt with carefully. Te Velde sees transformation as a synthesis between old and new, as a middle course between consolidation and large-scale demolition of the existing structures of neighbourhoods. Existing physical and social structures may offer qualities and opportunities for preservation. A balance has to be sought between preservation and necessary renewal. This research focuses on the housing level. On this level housing transformations are defined as interventions changing the differentiation of a building block. Examples are turning two or more houses into one, adding one or more storeys and turning storages on the ground floor into housing.
Housing transformations being environmentally preferred compared to demolition is, however, a premature belief. Methods and tools are lacking to be able to compare the environmental impacts of interventions in the housing stock [3]. The attention paid to methodological issues regarding environmental assessment of renovations is growing. Despite, there is not yet a general framework for comparing he environmental impacts of housing transformations against new construction. This paper aims to explain the search for the most eco-efficient strategies for sustainable housing transformations on the basis of two case studies. It discusses which housing transformation options are possible and how the environmental impacts can be assessed and compared to new construction.
Section 2 presents two case studies on housing transformations. In section 3 a solution for environmental comparison between housing transformations and new construction is discussed. Section 4 contains conclusions.
2
Case studies on housing transformations
Case studies in this research are two post-war housing areas, which presently face major restructuring operations: Morgenstond Midden in The Hague and Poptahof in Delft, both in the Netherlands. They are chosen, because the typology of the area as well as the housing in the area differs, but both of them occur a lot. Housing transformation options are described in section 2.1 and 2.2 respectively. Section 2.3 stresses the measures for both case studies to be environmentally assessed and compared to new construction.
2.1 Housing transformation options in Morgenstond Midden
Morgenstond Midden is a neighbourhood built in the fifties of the previous century, mainly consisting of tenement houses of three or four storeys (see fig. 1). Almost all housing in Morgenstond Midden will be demolished according to the renewal plans. The area has to be transformed into a compact urban garden city [4]. The borders of the neighbourhood will be surrounded by housing of five or six storeys. Along main streets houses will be built with four storeys; along other streets houses will be built with three storeys. The remaining inner area will be reserved for special housing environments and special housing types. The urban renewal plan is presented in fig. 2. This led to a housing programme of demolition of 2,350 houses and new construction of 1,650 houses [5].
Figure 1: Housing in Morgenstond Midden
The study on housing transformation options concentrated on two building blocks, which are circled in the upper left corner in fig. 2. The upper building block is part of the border of the area and consists of four storeys and 152 houses. The lower building block has 102 houses, divided over three storeys. Storages are deepened halfway. The four-storey block contains the following amount of apartments: 24 apartments with three rooms (type B), 24 apartments with two rooms (type C) and 8 apartments with five rooms (type A). The three-storey block is composed of: 15 apartments with three rooms (type B), 15 apartments with four rooms (type D) and 6 apartments with five rooms (type A). Most apartments are very small, varying from 44 until 67 m2. Current differentiation schemes are drawn in fig. 3.
It turned out that the building blocks have good opportunities for transformation. The load-bearing structure and dimensions do not form any barriers for technical solutions, which can attract new target groups. Possible new differentiation schemes are drawn in fig. 4. The four-storey block is through its border position suitable to extend with one storey. Then adding an elevator is feasible, so the three upper storeys can be transformed for the elderly. For that every two houses on the existing storeys have to be horizontally joined (M1). The new storey can be built similar to the existing storeys (M2). The lower two storeys can be vertically joined in maisonettes for starters at the housing market
(M3). Finally, the three-storey block is suitable for transformation into single-family houses (M4). In both blocks there is no need to do major interventions in the five-room apartments. This is the only type which has future value as it is.
Figure 2: Morgenstond Midden as compact urban garden city
Figure 3: Current differentiation schemes in Morgenstond Midden
Figure 4: New differentiation schemes in Morgenstond Midden
A storages A A A A A A A B B B B C C C C C C C C B B B B C C C C C C C C B B B B B B B B C C C C C C C C B B B B B B B B storages B B B D D D B B B D D D B B B D D D D D D B B B B B B D D D A A A A A A A storages A A A A A A A B B B B C C C C C C C C B B B B C C C C C C C C B B B B B B B B C C C C C C C C B B B B B B B B A storages A A A A A A A B B B B C C C C C C C C B B B B C C C C C C C C B B B B B B B B C C C C C C C C B B B B B B B B storages B B B D D D B B B D D D B B B D D D D D D B B B B B B D D D A A A A A A storages B B B D D D B B B D D D B B B D D D D D D B B B B B B D D D A A A A A A A storages A A A A A A A B B B B C C C C C C C C B B B B C C C C C C C C B B B B B B B B C C C C C C C C B B B B B B B B M2 M1 M1 M1 M1 M1 M1 M1 M1 M1 M1 M1 M1 M3 M3 M3 M3 M3 M3 M3 M3 M3 M3 M3 M3 M2 M2 M2 M2 M2 storages B B B D D D B B B D D D B B B D D D D D D B B B B B B D D D A A A A A A M4 M4 M4 M4 M4 M4 M4 M4 M4 M4 A storages A A A A A A A B B B B C C C C C C C C B B B B C C C C C C C C B B B B B B B B C C C C C C C C B B B B B B B B M2 M1 M1 M1 M1 M1 M1 M1 M1 M1 M1 M1 M1 M3 M3 M3 M3 M3 M3 M3 M3 M3 M3 M3 M3 M2 M2 M2 M2 M2 A storages A A A A A A A B B B B C C C C C C C C B B B B C C C C C C C C B B B B B B B B C C C C C C C C B B B B B B B B A storages A A A A A A A B B B B C C C C C C C C B B B B C C C C C C C C B B B B B B B B C C C C C C C C B B B B B B B B M2 M1 M1 M1 M1 M1 M1 M1 M1 M1 M1 M1 M1 M3 M3 M3 M3 M3 M3 M3 M3 M3 M3 M3 M3 M2 M2 M2 M2 M2 storages B B B D D D B B B D D D B B B D D D D D D B B B B B B D D D A A A A A A M4 M4 M4 M4 M4 M4 M4 M4 M4 M4 storages B B B D D D B B B D D D B B B D D D D D D B B B B B B D D D A A A A A A M4 M4 M4 M4 M4 M4 M4 M4 M4 M4
2.2 Housing transformation options in Poptahof
Poptahof is a neighbourhood with mainly gallery apartment houses, built in the sixties of the previous century (see fig. 5). There are 1,011 houses in eight building blocks of eleven storeys, six building blocks of four storeys and four building blocks with single-family houses. The urban renewal programme consists of demolition of the four-storey blocks and single-family houses and renovation of the eleven-storey blocks [6]. In fig. 6 the black rectangles in the left picture represent the blocks to be demolished. The dark-grey rectangles are the blocks to be renovated. They are the supporting structure for the composition of eight new sub areas, which are light-grey indicated in the right picture.
Figure 5: Housing in Poptahof
Figure 6: Creation of new sub areas in Poptahof
The study on housing transformation options concentrated on six of the eleven-storey blocks, which are of the same type. Each block has 99 houses totally, of which 77 are houses with four rooms (type A and B), 11 are houses with two rooms (type C) and 11 are houses with three rooms (type D). The size of the apartments varies between 61 and 73 m2. Storages are on the ground floor. Fig. 7 shows the current differentiation scheme.
In general gallery apartment houses from the sixties have more appropriate sizes than tenement houses from the fifties. Notwithstanding the load-bearing wall in the apartments, the sizes of naves and aisles offer good opportunities for
transformation of the building blocks. A new differentiation scheme is drawn in fig. 8 [7]. First of all, the problem of the very anonymous ground floors has to be solved. By replacing part of the storages and joining the ground floor with the first storey, maisonettes for families can be created (P4). Part of the storages can be replaced to the small two-room apartments next to the elevator (s). This makes the apartments at the other side of the elevator suitable for renovation for the elderly (P1). Apartment and storage together comply with the requirements for this type of housing. New construction at the head of the block can also be targeted for the elderly (P2). A new entrance with an additional elevator diminishes the load on the galleries. For starters making three-room apartments of four-room apartments will be sufficient (P3).
Figure 7: Current differentiation scheme in Poptahof
Figure 8: New differentiation scheme in Poptahof
2.3 Housing transformation measures
New differentiation of the housing stock naturally results in new floor plans and facade arrangements. In addition, such transformations also imply improvement measures. After all housing transformations have to compete with new
B storages C A A A A A D storages B C B C B C B C B C B C B C B C B C B C A A A A A D A A A A A D A A A A A D A A A A A D A A A A A D A A A A A D A A A A A D A A A A A D A A A A A D A A A A A D B storages C A A A A A D storages B C B C B C B C B C B C B C B C B C B C A A A A A D A A A A A D A A A A A D A A A A A D A A A A A D A A A A A D A A A A A D A A A A A D A A A A A D A A A A A D P3 bergingen P1 P3 P3 P3 P3 P3 bergingen P3 P3 P3 P3 P3 P3 P3 P3 P3 B P1 P3 P3 P3 P3 P3 P1 P3 P3 P3 P3 P3 P1 P3 P3 P3 P3 P3 P1 P3 P3 P3 P3 P3 P1 P3 P3 P3 P3 P3 P1 P3 P3 P3 P3 P3 P1 P3 P3 P3 P3 P3 P1 P3 P3 P3 P3 P3 P1 P3 P3 P3 P3 P3 A A A A A D P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 s s s s s s s s s s P4 P4 P4 P4 P4 P4 P4 P4 P3 bergingen P1 P3 P3 P3 P3 P3 bergingen P3 P3 P3 P3 P3 P3 P3 P3 P3 B P1 P3 P3 P3 P3 P3 P1 P3 P3 P3 P3 P3 P1 P3 P3 P3 P3 P3 P1 P3 P3 P3 P3 P3 P1 P3 P3 P3 P3 P3 P1 P3 P3 P3 P3 P3 P1 P3 P3 P3 P3 P3 P1 P3 P3 P3 P3 P3 P1 P3 P3 P3 P3 P3 A A A A A D P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 s s s s s s s s s s P4 P4 P4 P4 P4 P4 P4 P4
construction. Extension of the life cycle of forty to fifty years is aimed at. Moreover such transformations have to comply with building regulations for new construction. This means that thermal and sound insulation have to be improved anyhow. The quality of the transformation can be improved by adding own entries, enlarging outer spaces and renewal of installations. Table 1 lists all measures involved, except for option M2 and P2, because they concern new construction.
Table 1: Housing transformation measures
Measures Option M1 Option M3 Option M4 Option P1 Option P3 Option P4 Floor plan
Change of floor plan x x x
Limited change of floor plan x
Change of floor plan for elderly x x
Application of inside stairs x x x
Replacement of storages x x
Shell
Application of new facades x
Change of facade appearance x x x
Application of new entrance x
Outside space
Enlargement of balconies x
Application of terrace x
Application of gallery x
Application of elevator x
Thermal and sound insulation
Insulation of facade inside x x x
Insulation of facade outside x x x
Replacement of panels x x x
Insulation of roof inside x x x
Insulation of roof outside x x x
Insulation of floor x x x x x x
Application of floating covering floor x x x
Application of facing walls x x x x x x
Installations
Renewal of individual installations x x x
Renewal of collective installations x x x
3
Environmental comparison of housing transformations
against new construction
To assess environmental impacts Life Cycle Assessment or LCA is a widely accepted method. LCA is a method for the analysis of the environmental burden of products (goods and services) from cradle to grave, including extraction of raw materials, production of materials, product parts and products and discard, either by recycling, reuse or final disposal [8]. It is defined as the “compilation and evaluation of the inputs, outputs and potential environmental impacts of a product system throughout its life cycle” [9]. The product system is the total system of processes needed for the product, which in this case is a house. Inputs
and outputs are materials and energy, which enter and leave respectively the product system.
LCA of buildings is complicated, because each building has its own characteristics and contains a very large number of components and materials. Besides buildings have extremely large service lives in comparison with, for example, electronic equipment such as computers. Many changes occur during the service life of a building. However, current whole-building environmental assessment tools do not take into account changes in building characteristics over time. They are dealing with the environmental impacts of a building during its service life as it was originally constructed. They do not address the environmental impacts of building transformations [10], while these transformations may completely disturb the foreseen life cycle.
Fig. 9 shows what happens with the environmental impact when intervening in the original life cycle. The environmental impacts of the original house (Ioriginal),
with an assumed service life of 75 years, consists of: 1) the environmental impacts of construction in year 0, 2) the environmental impacts for replacements, maintenance, energy consumption and water consumption from year 0 until year 75, and 3) the environmental impacts of discard in year 75.
The environmental impacts of the original house increase by transformation in year X (Itransformation), while at the same time the life cycle increases. So
transformation in year X causes the following changes in the life cycle: 1) the life cycle extends from year X until year Y1, 2) the environmental impact raises due to addition of new components in year X, 3) the environmental impact decreases owing to removal of components which do not have to be replaced or maintained anymore from year X until year Y1, and 4) the environmental impact changes by altered energy consumption and water consumption from year X until year Y1.
New construction is expected to cause more environmental impacts by construction, but less environmental impacts by energy consumption and water consumption (Inew). Moreover, new construction is expected to have a longer
service life than housing transformations (Y2).
Figure 9: Comparison of environmental impacts
0 X 75 Y1 lifetime en v ir o n m e n ta l im p ac t Ioriginal Itransformation Inew Y2 0 X 75 Y1 lifetime en v ir o n m e n ta l im p ac t Ioriginal Itransformation Inew Y2
To be able to compare housing transformations with new construction lifetime is the most important issue. This is due to the fact that interventions like demolition or transformations are often needed before the expected service life of a house has expired. This is the case with renewal of the post-war housing stock in particular. At least the fact that environmental capital will be destroyed for the period from year X until year 75 has to be taken into account. In fact the environmental impacts have to be considered from year 0 until year Y1 and Y2 respectively. This is contrary to most current views that LCA implies looking at the same period of time [e.g. 11]. However, the choice of this period of time is completely arbitrary. Therefore it is argued that the average annual environmental impacts from year 0 until year Y should be looked upon. Then the environmental impacts of housing transformations against new construction are comparable.
4
Conclusions
The building blocks in Morgenstond Midden in The Hague as well as Poptahof in Delft are suitable for transformations. Besides new differentiation resulting in new floor plans and facade arrangements, improvement measures have to be taken with respect to outside space, thermal and sound insulations and installations. Related to new construction, in most cases housing transformations cause less environmental impacts by construction, but more environmental impacts by operation. Furthermore housing transformations are expected to have a lower life-cycle expectancy than new construction. As base for comparison average annual environmental impacts over the complete life cycle are suggested. The complete life cycle is the period from original construction up to and including discard at the end-of-life of housing transformation or new construction.
In the next stage of the research the housing transformation measures presented in section 2 will be environmentally assessed and compared to new construction on the basis of the method described in section 3. As LCA tool the Dutch tool Eco-Quantum will be used. Not only insight has to be gained in the environmental impact of housing transformations, but also on the modifications to be made to make the tool suitable for support in this kind of decisions. To investigate whether to transform or to demolish variables are the environmental impact, the amount of houses which will be transformed, the time of intervention and the expected lifetime of the intervention. Herewith the hypothesis can be tested that housing transformations have a lower environmental impact than demolition and new construction.
Of course it has to be bear in mind that housing transformations shall rarely be preferred from an environmental point of view only. Developments on the housing market are far more important. Generating knowledge on this subject, however, enables to take environmental considerations into account.
Acknowledgement
This research is partly financed by SBR, the Dutch Building Research Foundation.
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