On October 9-10 we had the privilege of attending the 44^th Air Infiltration and Ventilation Centre (AIVC) & 10^th Venticool conference titled “Retrofitting the building stock: challenges and opportunities for indoor environmental quality” held in Dublin, Ireland. The event covered 2 days filled with valuable insights and good company.

We organized and chaired the 90 minutes topical session “Ventilative cooling – latest and greatest. Importance of early design in the world of overheating mitigation using ventilative cooling” which attracted approximately 30 participants and featured lively discussions.  We extend our gratitude to presenters Paul D O’Sullivan (Munster Technological University) and Beat Frei (FREI WÜEST EXPERT) for sharing their views on a Ventilative cooling design process and how to tackle resilience and the cooling ladder ethos.

During the topical session we presented the latest content of the upcoming European Technical Specification (CEN/TS) called “Ventilative cooling systems – Design”.

This document sets the framework for designing ventilative cooling systems able to cope with the set criteria, from the early feasibility phase to the actual design phase for both residential and non-residential buildings. Furthermore, the document is a “system design” document much like prEN 15665 (under revision) and EN 16798-3 referencing existing EPBD standards e.g. thermal comfort criteria from EN 16798-1 or national regulations (as there is currently no system design standard for ventilative cooling systems).

The document serves as an important reference for prEN 16798-1-2 (thermal comfort) providing guidance on designing buildings without mechanical cooling while aligning with the chosen IEQ requirements; it is currently the only available document in Europe explaining how to design ventilative cooling systems. With a better early-stage design prediction method, such as the ventilative cooling potential method, a reference to our document in prEN 16798-1-2 revision will increase the likelihood of more resilient cooling solutions which could intermittently replace mechanical cooling solutions, when the outdoor conditions allow – both saving energy and reducing CO₂ emissions.

 Core Features of the Document:
 ✔️ 8 design steps – to follow when designing Free cooling systems
 ✔️ Cooling ladder ethos – prioritizing passive cooling solutions before moving to active cooling measures
 ✔️ Ventilative cooling potential method – that assesses outdoor air cooling potential in the early design phase
 ✔️ Flow diagram – enabling a simplified overview of the design steps and cooling ladder ethos including which choices to make
 ✔️ Resilience checks – enabling checks to enhance readiness for future extreme weather events (probably the first standard to include this)
 ✔️ Renewable energy for cooling calculations using ventilative cooling – as found in Renewable Energy Directive (RED II)

The document describes two design approaches establishing a framework for designing ventilative cooling systems. Each approach includes several elements, such as different ventilation requirements and conditions of use, among others, that can be selected on national basis and shown in the corresponding flow diagram.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

During the discussion part of the session, we received insightful questions and draw important conclusions such as:

• It all starts with IEQ requirements and perhaps we are currently setting too strict requirements. e.g. the temperature bands are too narrow, which might not be beneficial in some cases and we might end up oversizing the cooling systems.
• The importance of correct formulas to quantify thermal mass.
• Can the 8 design steps be used for all types of buildings?
• Is it a challenge that all non-residential buildings are handled together in this Technical Specification and that residential and non-residential buildings share the same design approach?
• The significance of micro-climate considerations at different design stages.
• Climate data is key to assessing ventilative cooling properly.

 

We greatly appreciate the constructive feedback which will inform future standard developments. It was a great pleasure to meet familiar faces and discuss important aspects of how to achieve good well-being in buildings, and how standards and legislation can help to support this.

For further discussion, feel free to reach out to us directly.

Christoffer Plesner – VELUX A/S and Jannick Roth – WindowMaster International A/S