ventilative cooling

Overheating in buildings is an emerging challenge at the design stage and during operation. This is due to a number of reasons including high performance standards to reduce heating demand by high insulation levels and restriction of infiltration in heating dominated climatic regions; the occurrence of higher external temperatures during the cooling season due to changing climate and urban climate not usually considered at the design stage; and changes in internal heat gains during operation are not factored in the design.

Examples of well documented case studies that use ventilative cooling (VC) to reduce the energy demand for cooling or overheating risk in new and refurbished buildings are valuable to the energy in buildings community. This report and associated brochures contains such examples and provides details on the design, control, operation and performance of the VC systems. The report aggregates and summarises all 15 case study buildings collected in subtask C of IEAEBC Annex 62. 

This design guide is based on the work of IEA-EBC Annex 62 “Ventilative Cooling” and the research findings of the participating countries.

This guide is designed for both architects and engineers to support the design of ventilative cooling systems especially in the early design stages.

This background report presents insights on recommendations into how ventilative cooling is integrated in EN standards, ISO standards, national standards, national legislation and national compliance tools. The information presented derives from feedback by IEA EBC Annex 62 experts of 11 countries who have completed a questionnaire. This gives a high level of insight into the current status, and thereby the recommendations to be given on the basis of this knowledge.

This report summarises the outcome of the work of the initial working phase of IEA ECB Annex 62 Ventilative Cooling and is based on the findings in the participating countries. It presents a summary of the first official Annex 62 report that describes the state-of-theart of ventilative cooling potentials and limitations, its consideration in current energy performance regulations, available building components and control strategies and analysis methods and tools.

In general, but in particular in nearly zero-energy buildings, there is a very strong tendency to drastically reduce the heating demand. One adverse side effect is that in doing so, it often increases the risk of overheating in summer and shoulder seasons. This is in particular, but not only, the case for lightweight constructions.

Computer classrooms present challenges for cooling because internal heat gains higher than typical classrooms. Focused on thermal comfort, this paper presents the results of a field and computational study of a computer seminar room in west England. A mechanical ventilation system with phase change materials thermal storage has been installed in the room to provide thermal comfort and indoor air quality. Monitored data of internal air temperature, CO2 and humidity were analysed and compared with current requirements for indoor air quality and comfort.

One-year monitoring results of environmental conditions in a UK seminar room where the Cool-phase® ventilation and PCM battery system has been installed indicate thermal comfort and good indoor air quality throughout the year. CFD analysis indicates that air temperature and air distribution is uniform at occupants’ level.

Research indicates that low-energy dwellings are more sensitive to overheating than regular dwellings. In this research the ventilative cooling potential of low-energy dwellings is considered. A low-energy dwelling based on the Active House concept, “House of Tomorrow Today” (HoTT), has been investigated as representative for low-energy dwellings in general. A computational model of the house was created with the software TRNSYS (in combination with CONTAM) and this model has been calibrated with actual (intervention) measurements in the HoTT.

The increasing number of highly insulated and air tight buildings leads to the concern of indoor environment overheating and related comfort and health issues. This can already happen in a temperate climate as found in the Netherlands. This work studies the ventilative cooling process as a possibility to avoid overheated dwellings. A monitored dutch passive house was modelled in Trnsys and the impact of increasing air flow rates on indoor temperatures was simulated. The most overheated zone was chosen to be analysed.