Green steel (also known as ‘low-emission steel’ or ‘climate steel’) is a collective term for steel whose production reduces emissions (in particular CO₂ equivalents = CO2e) compared to the production of conventional steel, usually by dispensing with fossil raw materials such as coal as energy sources. This elimination is made possible in particular by using so-called electric arc furnaces, which are not operated with fossil raw materials like conventional blast furnaces, but with electricity (from renewable energy sources).

The amount of CO₂e saved during the production of the steel depends on which Green Steel is specifically compared with which conventional steel. For example, the production of the conventional steel we use generates approx. 2570 kg CO2e per tonne of steel. In comparison, the CO₂e emissions from the production of the Green Steel we use are around two thirds lower and amount to approx. 877 kg CO2e per tonne of steel. (Further information on this steel can also be found in the answer to the third question).

For galvanised steel components of ventilation and air handling technology appliances, WOLF uses steel produced from at least 75% recycled scrap in an electric arc furnace with electricity from renewable sources (see the Environmental Product Declaration ‘epd-steel’ for this steel), in a so-called ‘Book&Claim’ process (see the answer to question 6 for this process), which is produced from at least 75% recycled scrap in an electric arc furnace using electricity from 100% renewable energy sources.

AHU products, including those from WOLF, are made of different materials. Green Steel is used for galvanised steel materials. Their proportion in an air handling unit varies depending on the unit, which means that the CO₂e savings resulting from the use of Green Steel instead of conventional steel also depend on the specific unit. Secondly, the scope of consideration must be defined. In the case of a ‘KG Top 2015’ (air volume flow 10,000m³/h), for example, the cradle-to-gate CO₂e emissions of this appliance are reduced by around a third with the CO₂-reduced steel we use, instead of the conventional steel we use. According to EN 15804 (A1-A3), cradle-to-gate refers to the analysis of the CO2e emissions and other measured environmental effects of a product from raw material extraction (cradle) to the factory gate (gate). EN 15804 sets out basic rules for the preparation of Environmental Product Declarations (EPDs) for construction products. These contain the results of life cycle assessments for the respective building materials as an essential component and form the basis for assessment and certification systems that evaluate the environmental performance of buildings.

Green Steel can be booked as an option for every WOLF Air Handling unit using a so-called ‘Book&Claim’ procedure (see the answer to the 6th question for this procedure).

For technical production reasons, it is currently not possible to ensure with reasonable effort that every air handling unit ordered and delivered to you is actually manufactured with ‘Green Steel’. In accordance with WOLF's ‘Book&Claim’ procedure, we therefore use the calculated proportion of the Green Steel you have booked, which may not be used for an AHU you have ordered and delivered to you, but elsewhere in the production of AHUs within a period of six months from receipt of the order confirmation. For this purpose, we balance the booked and consumed quantities of Green Steel and a monitoring system monitors and ensures the use of the booked quantities in production on the basis of the technical data sheets (of the AHUs ordered with and without the Green Steel option), which show the proportion of galvanised steel materials.

When taking up the Green Steel option, our customers receive a comparative calculation on the quotation data sheet showing the ‘cradle-to-gate’ CO₂e footprint (see the answer to the 4th question) of the appliance in question and the CO₂e savings that result compared to an appliance with the conventional steel we use (for an example of the ‘KG Top 2015’ appliance (air volume flow 10,000m³/h). This applies regardless of whether the specific appliance was produced (entirely) with Green Steel, as the calculated proportion of Green Steel that may not have been used for the appliance in question is used elsewhere in the production of air handling units at WOLF (see the answer to the 6th question).

Green steel is more expensive than conventional steel, as the production is complex and innovative technologies and electricity from renewable energy sources are used. However, WOLF believes that the higher price is offset by a reduction in CO₂e emissions.