City of Helsinki analysed the costs and carbon footprint of renovation and new constuction

Many Finnish cities are working to increase the efficiency of land use and condense the urban structure by means of complementary construction, tearing down old buildings and constructing new ones. The City of Helsinki wanted to determine the construction costs and emissions of two different methods: renovation and heightening versus dismantling and construction. Sweco conducted the cost analysis and carbon footprint calculation for two residential blocks of flats.

The City of Helsinki aims to achieve carbon neutrality by 2035. In the coming years, the Ministry of the Environment will also be releasing guidelines for calculating the carbon footprint of properties. One way to achieve the goals is to increase land use efficiency in residential areas.

“Tearing down suburban blocks of flats to make way for new buildings is often brought up as a means towards denser land use. This is a worrying trend since it may not be the smartest thing to do in terms of sustainable development,” says Timo Karhu, housing development architect for the City of Helsinki.

The climate network formed by the mayors of the six largest cities in Finland has proposed that a larger proportion of new residential buildings, public buildings and additional buildings intended to complement existing districts should be made of wood.

“A wooden building is a carbon sink and wood is a renewable material, which causes less carbon dioxide emissions to produce than concrete,” Karhu says. The Helsinki Housing Production Department (Att) has already developed a number of wooden-framed blocks of flats and new projects are being planned. “In this context, the idea of heightening blocks of flats requiring renovation with additional wood-structure floors has been brought up as an alternative to demolition.”

Is construction cheaper than renovation?

Att commissioned a survey on the renovation and heightening as well as demolition and construction of two rental blocks of flats owned by Helsinki City Housing Company. Sweco carried out the partial calculations for the cost analyses of both alternatives.

“As regards the renovation, it was noted that the foundations would need to be enforced and the interior spaces refurbished, in addition to integrating a lift, replacing the concrete shell elements with wooden structures, increasing thermal insulation and heightening the building with two extra wooden floors,” Karhu lists. “The construction cost analysis indicated that a preserving renovation would, at least for the properties in question, be slightly more affordable than the construction of new buildings.”

The carbon footprint calculation revealed the emission impacts of the two operating models

Next, the focus was shifted to determining the CO2 emissions of the two operating models. Sweco’s carbon footprint calculation also entailed an assessment of in-service energy consumption and investment costs as well as architectural modelling.

“The carbon footprint calculation specifies the sources of emission throughout the building’s entire life span,” says Kari Nöjd, project manager at Sweco. The calculations indicate that the renovation and heightening of the two residential buildings would yield a smaller carbon footprint than constructing new buildings. “Lifecycle energy consumption and the production of the construction materials have the most significant impact. The proportion of transport and demolition is relatively small.”

Renovation quality determines energy efficiency

Renovation rarely leads to the same level of energy efficiency as the construction of a new building. However, improving energy efficiency is essential for reducing the carbon footprint.

“It’s possible to renovate properties to a state where the resulting emissions are lower than in construction,” Nöjd says. As a matter of fact, the aim in this context is not to restore the buildings to the original condition. “Among other things, modern energy-efficient building automation must always be integrated into residential properties.”

Land use solutions are sparking a great deal of discussion in the context of city services and administration, and wide-ranging interest has been expressed towards the results of the analyses.

“Thanks to the facts provided by the consultants, we can justify that condensing residential areas through renovation and heightening can be financially feasible and in line with the city strategy,” Karhu says. “It would seem that preserving solutions are available for increasing the efficiency of land use.”