Researchers at ETH Zürich researched the most effective renovation strategies for reducing greenhouse gas emissions and found that using biobased building materials like straw and hemp have a lot of potential.

In Switzerland, about 2.8 million buildings account for some 40 per cent of the country’s energy demand. More than half of these are still heated using fossil fuels like oil and gas, and stem from a time before effective energy standards. Renovating buildings to improve their energy efficiency is a crucial step for Switzerland, but also many other countries, to achieve their climate targets.

Traditional renovations aimed at reducing energy consumption involve two measures: insulating the shell of a building, and replacing fossil fuel based heating systems with ones running on renewable energy.

The study focused on six buildings from between 1911 and 1988 to provide a representative sample of all Swiss buildings. For each, the researchers calculated the greenhouse gas emissions that would result from a variety of renovation measures over the course of a 60-year building life cycle from the time of the renovation. Measures included replacing existing heating systems with newer ones like heat pumps, and installing layers of insulation of different thicknesses.

They used conventional insulation materials (EPS, fibreglass, mineral wool, cellulose fibres) and insulation materials from fast-growing plants (like straw and hemp). If the CO2 emission from manufacturing are taken into account, manufacture of conventional insulation materials can be very high, sometimes high enough to cancel out the positive effects they have on energy consumption when used in the renovation of a building. Building materials made from renewable raw materials have a much lower carbon footprint. Moreover, they offer the added bonus of absorbing CO2 from the atmosphere while they grow and storing it long-term in the building.

Relacing oil and gas heating systems was found to be the cheapest and most effective way to cut greenhouse emissions. However, there is also a large role to play for biobased insulation materials. According to the researchers, Switzerland’s buildings could cut their greenhouse gas emissions by up to 87 percent primarily by switching to heat pumps or wood pellets, but also by using bio-based building materials such as straw bales, hemp mats and hempcrete.

Photo: Atelier Schmidt