Buildings are the biggest climate killer: They cause ten billion tons of CO2 per year worldwide. This occurs when generating heat and electricity and during construction. That is an average of around 1.3 tons of CO2 per year per inhabitant.

According to a UN study, the building sector caused 37 percent of energy-related CO2 emissions worldwide in 2021 – more than industry (30%) and the transport sector (22%).

How can these high emissions be reduced and what measures can we take to live sustainably, cheaply and well?

In the last hundred years, not only has the number of people on earth increased, but also their use of space. At the same time, incomes and the number of people living alone have increased dramatically. But the differences are huge. While in Nigeria a person lives on an average of six square meters of living space, in Turkey it is 18, in Brazil 24, in China 30, in the EU 38 and in the USA 75 square meters per person.

In Germany, the average living space per person has more than tripled from 15 square meters to 48 square meters since 1950. Elderly people in particular, whose children have left home, have a lot of space here: on average, senior citizens live in more than 60 square meters of living space.

The more apartments and houses are built and occupied, the more energy is needed for heating and electricity, and the more CO2 is produced by new buildings.

Older buildings need a lot of energy for heating. This is expensive and eats up resources. Insulation and a modern ventilation system can save up to 90 percent energy in old buildings.

In addition, heating costs can be reduced if less living space is used.

The heating requirement can also be covered in a more climate-friendly way with biogas, wood or pellets instead of fossil fuels. However, since these resources are becoming increasingly scarce and therefore more expensive, experts recommend heating with heat pumps in particular. They draw environmental heat from the ground or the air, are powered by electricity and thus generate up to seven kWh of thermal energy from one kilowatt hour (kWh) of electricity.

This technology does not cause any harmful fine dust and, if green electricity is used, no CO2 either. In Scandinavia, buildings have long been heated with heat pumps and district heating networks have been operated with large heat pumps. In combination with solar thermal energy, biomass and deep geothermal energy, some district heating networks there are already almost climate-neutral today.

The electricity requirement in buildings can be significantly reduced by using economical heating pumps, energy-efficient refrigerators and LEDs. With photovoltaics on roofs and facades, electricity can be generated cheaply and climate-friendly directly at the house.

In sun-poor Germany, solar power from the roof of a house with a new system now costs less than ten euro cents per kWh. That is less than a quarter compared to electricity from the grid, which costs around 40 cents per kWh on average. The investment in modules on the roof is amortized in 5 to 15 years and then they generate around two decades of free electricity.

A lot of CO2 is emitted during the construction of buildings, 0.5-0.8 tons of CO2 per square meter of living space. That is about 50 to 80 tons of CO2 when building a new 100 square meter apartment. For comparison: In India, CO2 emissions per capita are two tons per year.

The emissions are mainly caused by the production of cement, lime and gypsum (25%), by the construction itself (10%) and by the production of building materials such as insulating boards (8%) and metals (8%).

Alternative building materials such as wood and renewable insulating materials such as straw can drastically reduce CO2 emissions in new buildings, by around 50 percent in Germany.

Upgrading older buildings instead of building new ones also saves a lot of CO2 and reduces costs. Renovation usually costs less than a quarter compared to new construction. The CO2 emissions from construction and operation can be more than halved.

Architects, scientists, environmental organizations are calling for a rethink on the part of urban planners and those planning to build. Demolition and new construction should be avoided if possible, the refurbishment of old buildings must become the norm, so the demand.

In view of the housing shortage and climate crisis, a rethink is also required in society and politics. “The area in which people live in Germany today would be sufficient for 200 million people – if they were satisfied with an area that was common in the 1960s,” says the sociologist Maike Böcker.

She works at the Institute for Advanced Study in the Humanities in Essen and describes the dilemma and the challenge of the climate-friendly society in her book “How will less be enough”. Around 83 million people live in Germany today, and more than eight billion worldwide.

In order to comply with the 1.5 degree limit, the Wuppertal Institute think tank calls in its study to stop and reduce the growing demand for living space per capita “through intelligent and flexible forms of use” in Germany.

In one scenario, the Technical University of Graz (Switzerland) assumes that, despite the increasing population, global energy demand would have to fall by 40 percent in order for the 1.5 degree limit to be met. The researchers recommend a global average living space of 30 square meters per person.

Experts see great potential for savings in senior citizens in particular. In industrialized countries like Germany, many older single people or married couples live in rather large apartments or houses after the children have moved out, which are often not equipped for their age. At the same time, there is a lack of living space for young families, especially in cities.

Targeted advice and offers can help here, says urban planner and economist Daniel Fuhrhop. “This can be, for example, moving into a smaller apartment, as well as converting existing apartments and creating granny flats, for example. Subletting or living with other people are also options. There are many great and tried and tested models.”

Some universities are now placing students who can live cheaply with senior citizens in exchange for household chores. Residential projects for old and young with small individual residential units and lots of common areas such as gardens, workshops, studios, laundry and fitness rooms are also becoming increasingly popular. With this model, office space and guest rooms can be booked at low cost for a certain period of time. Many residents appreciate such community quarters, they spend a lot of time together, get to know each other better and support each other.

Author: Gero Rueter

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The original of this article “How do we live in a climate-friendly, cheap and good way?” comes from Deutsche Welle.