Renovate or replace?

This Issue This is a part of the Sustainable design feature

By - , Build 100

Should a property owner renovate, or demolish and rebuild? New research from the Netherlands sheds some light on environment impact aspects of this question.

When considering upgrading, the property owner always has a dilemma – whether to maintain a building with some minor intervention, or demolish it and take the opportunity to create a modern, up-to-date structure which meets today’s inevitably higher standards. This may attract higher rentals or better meet the needs of those who are using it. This dilemma is faced whether it is a house, school or commercial building.

Beacon Pathway Ltd is developing an assessment process for decisions on sensible upgrading or replacement of existing homes to enhance the sustainability of our residential built environment. The work will be informed by some recently-published research from the Netherlands, which looks at decision-making for urban renewal. Though the houses are quite different from New Zealand’s, the principles of the assessment method which the research used can be applied to all building types.

Must meet users’ needs

The research highlighted that the first thing to consider is whether, if renovated, the building would meet the needs of its users. In most urban renewal districts in the Netherlands the existing stock does not meet needs for size and differentiation of today’s users. Consequently there has been large-scale demolition and construction of new buildings.

Environmental impacts

The environmental impacts of different types of construction work are another consideration. Using case studies the research compared the impacts of four scenarios:

  • maintenance (ordinary building maintenance)
  • consolidation (insulation measures)
  • transformation (change of floor plan to meet new needs, with upgrading to meet new Code requirements)
  • rebuilding (demolition of the old building and reconstruction with a new floor plan).

The case studies involved multi-storey residential blocks in two neighbourhoods – Morgenstond Midden (The Hague), built in the 1950s, and Poptahof (Delft), built in the 1960s. The Morgenstond case was a 4-storey block containing 56 dwellings, with a total floor area of 3,016 m2. The transformation (or rebuilding) delivered a 5-storey building with 40 dwellings and 3,765 m2 floor area – a significantly greater average floor area and a wider range of dwelling types. The Poptahof case was an 11-storey building with 99 dwelling units, with an area of 6,319 m2. The transformation kept the same floor area but reduced the number of dwellings to 89.

Life cycle assessment of impacts

Several methods were used to quantify the environmental effects of the work, including Life Cycle Assessments (LCA) of impacts on the environment using a Dutch tool, EcoQuantum. The researchers note that the LCA work was hampered by poor database accuracy – an issue faced with LCA tools in New Zealand too.

The issues are quite complicated. For the Morgenstond building, the LCA analysis showed transformation had less environmental impact than maintenance on nine of the 10 environmental indicators in the LCA analysis, and was about equivalent on the 10th. On the Poptahof building, however, transformation had less impact than maintenance on only two of the indicators. One reason for this is the substantial increase in floor area created in the Morgenstond transformation, providing a lower impact per square metre of usable space. Payback periods for total energy use (including the materials embodied energy) for the three interventions compared against maintenance are in Table 1.

Transformation gave ‘better’ environmental impact answers than rebuilding in virtually every respect. It led to reduced energy and water use than maintenance, similar to rebuilding, and created much less waste than rebuilding. But for transformation to be possible, the building must have sufficient flexibility – for instance, the construction should not rely on load-bearing inner walls.

Social and economic issues

Sustainability is not just about the impact of the building shell change on the physical environment, which is the Dutch report focus. There are indirect hints that ‘people’ aspects have been considered and the transformation enhanced these too by providing a wider range of types of dwellings. Of course, it is very difficult to change aspects of neighbourhood sustainability simply with transformation (or rebuilding) of single existing buildings.

The third leg of the sustainability issue is an economic one. The report provides no information on the economic impacts of each of the options studied. The most environmentally-benign solution is possibly not best if it is so expensive that over the whole life cycle of the building other options exist with a lower initial and/or operating cost but a slightly higher environmental or social impact.

Table 1: Payback in energy use compared with simple maintenance.
  Morgenstond, The HaguePoptahof, Delft
Consolidation immediate 7 years
Transformation 10 years 25 years
Rebuilding 18 years 55 years

For more

The report by Itard and Klunder on the Dutch research was published in ‘Building Research and Information’, 35(3), pages 252–267.

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Articles are correct at the time of publication but may have since become outdated.