In the DRAFT COMMISSION NOTICE from 19th December 2022 with FAQs addressing the interpretation and implementation of certain legal provisions of the EU Taxonomy Climate Delegated Act, the Question 40 replies to the possibility for curtain walling to qualify for taxonomyalignment under Section 3.5.
According to the given answer, Curtain Walling will fall under the windows criteria with U-value ≤ 1.0 W/(m²K) if at least 80% of the surface is glazed and transparent. If the glazed and transparent area is less when some opaque panels are included, the criteria for wall systems will apply with U-value ≤ 0.5 W/(m²K).
As Curtain Walling fulfils rarely at least 80% of glazed and transparent surface and U values usually are higher than 0.50 W/(m²K) the FAQ 40 does not solve the problem that the product cannot comply with the EU Taxonomy.
Differentiating the criteria for Curtain Walling to fall into either the category of windows or walls does not seem to take fully into account the characteristics of Curtain Walling and does not give a fair evaluation. Curtain Walling is rarely composed in a way that can be compared with a simple wall.
The nature of Curtain Walling is indeed that can be used to create diversity in the façade with the variety of transparent and opaque areas. This gives a large flexibility in the architecture of the façade as well as the use of the rooms inside the building. This ensures good energy performance combined with the admittance of solar gain, daylight and view.
In the Annex are some examples from recent projects in Denmark, Norway and UK made of high performing products showing the diversity of Curtain Walling, however also showing that the suggested distinction between transparent and opaque areas is not reasonable and thus the criteria for Curtain Walling should be linked to Windows only, and without conditions. This is also a simple approach.
We also would like to remind to the Joint call to revise criteria for windows in the EU Taxonomy Climate Delegated Act (October 2022) which is also valid for the situation of Curtain Walling. The setting of a pan European maximum U-value for Windows and Curtain Walling does not serve the climate and the environment, because it does not allow to factor in geographical and climatic differences to optimise resource and energy use. It rather promotes highly insulated windows and curtain walls everywhere in the EU irrespective of the climatic conditions.
In the medium term the EU Taxonomy criteria should be revised to also factor in the ‘Energy balance’ approach for transparent products like Windows and Curtain Walling by replacing the present pan-European maximum U-value by values for Heating energy demand and/or Cooling energy demand according to different climatic conditions.