There has been an overall lack of ventilative cooling integration in existing European technical documents regarding “system design” and “performance” aspects, and therefore work relevant to ventilative cooling applications started up in CEN/TC 156 and ISO/TC 205 in various working groups since 2017.

These CEN and ISO projects have the scope of making technical documents focusing on setting design aspects to achieve the set ventilation requirements for Ventilative cooling systems (natural, mechanical, hybrid) as well as Ventilation systems (natural, mechanical, hybrid). The target groups are both national committees and regulators/designers. The aim is that precise requirements for design are to be put in open templates to be filled in by the countries to ensure compliance with national legislation on e.g. ventilative cooling.

Ventilative cooling is an air system that cools a building using ventilation air from outside at its actual temperature and humidity. Air transfer may be by natural, mechanical or hybrid means. Generally ventilative cooling reduces the energy consumption of mechanical cooling systems while maintaining thermal comfort.

Generally, there is good development in these projects, with a plan to coordinate among the working groups in CEN and ISO to eliminate overlaps, like for example on ventilation definitions and type of requirements.

The following projects relevant to ventilative cooling applications will be developed within 2-3 years in CEN:

• “Ventilative cooling systems” (covers both residential and non-residential buildings)
  • Main focus: Thermal comfort (reduce cooling loads and prevent overheating)
  • Document type: A CEN Technical specification (CEN/TS)
  • Work started up in WG/21 in CEN/TC 156
• “Natural and Hybrid ventilation systems in non-residential buildings”
  • Main focus: Indoor air quality
  • Document type: A CEN Technical specification
  • Work started up in WG/20 in CEN/TC 156
• “Ventilation for buildings – Ventilation systems in residential buildings – Design”
  • Main focus: Indoor air quality
  • Document type: A CEN European EN standard (merging EN 15665 and CEN/TR 14788)
  • The aim is also to expand the sections on Natural and Hybrid ventilation systems by fully supporting the Performance based design methodology
  • Work started up in WG/2 in CEN/TC 156

And the following project will be developed within 2-3 years in ISO:

• “Design process of natural ventilative cooling systems in interaction with mechanical cooling systems in non-residential buildings”
  • Main focus: Thermal comfort (reduce cooling loads and prevent overheating)
  • Document type: ISO standard
  • It has been decided to update the scope to also include hybrid solutions (interaction of natural ventilative cooling and mechanical cooling systems
  • Work started up in ISO/TC 205, WG/2, SC/2

These technical documents will describe design aspects to achieve the set ventilation requirements of ventilative cooling systems. The documents will likely include a simple to use design method to estimate the “Ventilative cooling potential” (IEA EBC Annex 62) [3] to thereby find the amount of time per year ventilative cooling could be used for the given project depending on building and location. This method will be updated with relevant equations from EN ISO 52016-1 (to include thermal mass) for full alignment across the CEN projects.

The initiated projects are foreseen to be released hopefully in late 2023 and of course support but not overlap the content of the EPB(D) standards [1]. The technical documents are a good opportunity to define design aspects of ventilative cooling and natural and hybrid ventilation systems on the European and International scene by applying findings from the Venticool platform [2] and the final deliverables of the IEA EBC Annex 62 reports [3].

Christoffer Plesner, VELUX-Denmark & Jannick Roth, WindowMaster-Denmark