Dabrović: We are paying the price of growth, Zagreb is expanding like an American city

For every square meter of built apartment or house, one ton of carbon dioxide is produced, and one adult oak tree is needed for its absorption – this is just one of the vivid examples presented by Marko Dabrović, architect and co-founder of the 3LHD studio, in his lecture at the 8th Central Conference on Sustainable Construction. Dabrović emphasized that the problem is not only in the emissions of the construction sector but in the way cities grow.

– The density of the city is one of the key parameters of sustainability. Zagreb has an area six times larger than Paris, yet two and a half times fewer inhabitants. In recent decades, it has been expanding like an American city. In terms of population density, it is comparable to Detroit – said Dabrović.

Negative consequences

Such spatial dispersion, he warns, has a whole range of negative consequences. Zagreb is among the cities with the worst traffic congestion in Europe, and its residents lose about seven days of life per year in traffic. In addition to ecological, there are also financial consequences: many households must have two cars, spending more on fuel and insurance, which directly impacts health and quality of life.

– The second car, fuel, and maintenance of two vehicles can cost a family up to eight thousand euros a year – said Dabrović.

Housing dispersion, he added, significantly burdens the city budget as the costs of developing and maintaining infrastructure increase as population density decreases.

Uncontrolled expansion

– Urban sprawl, or uncontrolled city expansion, requires significantly higher investments in roads, sewage, and public lighting. Greater dispersion of the city costs two and a half times more than in the case of more compact construction. Paradoxically, these more distant zones are twice as cheap in utility fees compared to the city center – he pointed out.

In his opinion, the utility fee must become a tool of spatial policy, not just a fiscal instrument.

– Zagreb urgently needs to change the utility fee collection system to encourage development in areas where the city is already investing in infrastructure and in brownfield areas – said Dabrović.

He also proposed the introduction of a differentiated utility contribution system, where the contribution on the periphery would be significantly higher due to the lack of infrastructure, while in the center, where infrastructure already exists, it would be lower.

Dabrović also presented a series of visualizations showing the hidden costs of urban sprawl – longer roads, greater distances to connections, and increased energy needs.

He then spoke about embedded CO₂ emissions in construction.

– The construction sector is globally responsible for 39 percent of CO₂ emissions – 11 percent comes from material production, and 28 percent from the construction itself. Every new square meter we build carries one ton of CO₂. To compensate for that, one large oak tree, 10 to 14 meters tall, is needed. Imagine your apartment, then multiply the square meters by the number of oaks we would need to plant – noted Dabrović.

If a building is not located in the city center but on the periphery, the emissions resulting from daily transport can be greater than those produced by the construction itself.

In other words, the location of the building often has a larger carbon footprint than the materials themselves, as daily commutes, longer traffic routes, and dispersed infrastructure generate the largest part of total CO₂ emissions.

According to estimates, to offset the emissions of one car over ten years of use, about 10,000 square meters of forest is needed, which corresponds to the area of one city park. An average car emits about five tons of CO₂ per year, or 50 tons over ten years, which means that to neutralize the emissions of one vehicle, 50 adult oaks should be planted.

Unlike most EU countries, Croatia is experiencing an upward trend in greenhouse gas emissions, further emphasizing the importance of spatial planning and reducing dependence on cars in everyday life.