Ventilative cooling as part of a resilient cooling strategy

Ventilative cooling can be in many circumstances a key element in a sustainable strategy for thermal comfort during periods of cooling demand. However, its potential can be very low if not combined with a good overall building design and solar control strategy. Furthermore, studies on the performance of existing low energy cooling systems (like ventilative cooling) concluded that even with current satisfactory performance, these technologies fail to function adequately in the extraordinary scenarios or shocks (e.g. high occupancy, power failure, high humidity production, pandemics etc. ).

A generally agreed definition of ‘resilient cooling’ is not yet available but the following description gives a good indication of the resilience of a building as an “ability of the building to withstand disruptions caused by extreme weather events, man-made disasters, power failure, change in use and atypical conditions; and to maintain capacity to adapt, learn and transform”.

In line with the scope of IEA EBC annex 80 Resilient Cooling of Buildings, the venticool platform has broadened its field of attention to  resilient ventilative cooling strategies.

Ventilative cooling in standards, legislation and energy performance calculations

Because of their increasing impact on building design options, energy performance regulations are undoubtedly key market drivers. This is a specific concern for ventilative cooling strategies as they require rather mature assessment methods for thermal comfort and ventilation losses to be correctly accounted for. More specifically, standards, legislations and compliance tools need to include:

• Assessment of overheating, e.g.:
  • Utilizing thermal comfort indicators, including adaptive temperature sensation
  • Utilizing energy performance indicators
• Assessment of resilient natural and mechanical ventilative cooling
• Design calculation methods that fairly treat resilient natural ventilative cooling for determination of air flow rates including e.g. the dynamics of varying ventilation and the effects of location, area and control of openings

IEA ABC Annex 62 Ventilative Cooling has pointed out limitations regarding the design of ventilative cooling systems in CEN, ISO and national standards as well as national regulations as e.g. used in energy performance regulations which are detrimental to ventilative cooling.

These include the poor handling of usage profiles and control strategies, in other words, assumptions on by how much and when the airflow rates are increased to meet acceptable thermal comfort conditions. Furthermore an evaluation of the “ventilative cooling potential” is needed for the designer to make the right decisions in the early design phase, showing for how long throughout a year pure ventilative cooling solutions are possible and when supplementary systems could be used. Actually, a design tool by the IEA EBC Annex 62 was developed called “ventilative cooling potential tool” to help with this.

In fact, adequate credit for ventilative cooling should account for thermal comfort criteria as well as ideally, indoor air quality, visual comfort, and noise. It should reflect the effective cooling potential which greatly varies within a single day, calling for rather sophisticated calculations seldom used in regulations. The good news is that CEN and ISO have ongoing activities for a better assessment of ventilative cooling through new work items expected to be published around 2023.

The regulatory implementation of ventilative cooling strategies differs from country to country and therefore attention to the national approaches also falls within the scope of venticool.