Which one produces fewer emissions, new construction or renovation?

Construction legislation is changing, and low-carbon construction is given more priority. Buildings should be sustainable, low-carbon and adaptable. Material emissions can be minimised by saving the existing structures.

Renovation construction produces fewer emissions during the material and construction phase than new construction, if the reinforcement steel frame and load-bearing structures that cause high carbon dioxide emissions are saved.

Renovation projects almost always have a smaller carbon footprint during the material and construction phase. However, the carbon footprint can be larger when looking at the entire life cycle. It is affected by the extent of the renovation measures, possible extensions and the level of energy efficiency achieved. If a renovated building is less energy-efficient than a new building, the annual emissions of the new building are lower during its use, thanks to lower energy consumption.

When comparing new construction and renovation projects, the energy efficiency of the latter is influenced by the choices made during the renovation. They determine emissions during the use phase. The carbon peaks of the material and construction phase are nearing each other in the different options, which means that the carbon footprint of renovation can grow quickly and exceed the carbon footprint of new construction over the examined period.

Based on research, the carbon footprint is usually smaller in renovation projects for the first 20–30 years, after which it exceeds the carbon footprint of new construction.

Life cycle is a key perspective when looking at environmental impacts

The findings above are the most important conclusions of my thesis. The aim of thesis was to find answers to the following questions:

  • How does renovating an old office building instead of building a new one affect emissions over the building’s life cycle?
  • What factors influence the life cycle carbon footprint in new and renovation construction?
  • How do the emissions impacts differ in new and renovation construction at each phase of the life cycle?

In other words, the thesis compared the life cycle emissions impact of demolishing new construction with the emissions impact of renovation construction.

Life cycle is a key approach when examining the environmental impacts of construction.  Emissions are produced during the material phase (acquisition of raw materials and manufacturing of building materials), the use phase (use and maintenance of the building and energy and water consumption) and the demolition phase (transport and treatment of demolition waste).

In my thesis, I calculated the carbon dioxide emissions of an office building during a life cycle of 50 years from the perspective of both new and renovation construction. I also considered the emissions impact of demolishing the structures before construction. I took into account the connection to the geothermal heat system and the impact of solar panels on the building’s life cycle emissions.

Low-carbon solutions and adaptability

New construction has been studied and steered in a more low-carbon direction, and solutions have been developed by material suppliers, users and contractors. In new construction, more than half of the emissions originate from the manufacture of products and materials, before the construction phase.

In renovation projects, most of the emissions are produced during the use phase. The majority of these are emissions from the consumption of energy (50–60 per cent of the carbon footprint). In the carbon footprints of both construction methods, the share of construction and the end of the life cycle were less than 5 per cent each. Therefore, there is no clear answer to the question ’’Which one produces fewer emissions, new construction or renovation?’’.

Low-emission, flexible and long-lasting materials and structures minimise emissions from materials. Emissions arising from the use of buildings can be reduced by promoting the efficient and flexible use of energy and space.

In renovation construction, attention should be paid to the achieved level of energy efficiency and its emission impacts. From the point of view of the tenants, it is also relevant to consider how efficiently the spaces can actually be used in the different options. Spaces should be made as flexible as possible in order to meet the needs of users easily, reduce the amount of materials required and, consequently, cut down emissions.

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Tiia-Lotta Tuominen wrote a thesis for YIT. The thesis compared the life cycle emissions impact of demolishing new construction with the emissions impact of renovation construction.

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