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The current development in building energy efficiency towards nearly-zero energy buildings (nZEB) represents a number of new challenges to design and construction. One of the major new challenges is the increased need for cooling arising in these highly insulated and airtight buildings. The cooling demand depends less on the outdoor temperature, and more on solar radiation and internal heat gains. This naturally gives better potential for the use of ventilative cooling technologies, because the cooling need is not only in summer, but actually all year round.
For residential buildings, the design process is much more simplified than for commercial buildings and is to a very large extent based on experiences and rules of thumb and the need for cooling is underestimated or might not even take it into account. Therefore, developed solutions to address cooling issues available for residential applications are very limited, often too simplified and might not be well adapted for practical application. Finally, homeowners of might not know how to effectively reduce the overheating in their building and their behaviour might instead actually increase the problem.
For offices and other non-residential buildings, the challenges are different and mainly related to the development of new approaches towards reduction of the existing energy use for cooling. However, due to thermal comfort issues and the risk of draught limited temperature differences between supply air and room can be utilized making heat recovery or air preheating necessary. As a result, the energy and cost advantage of utilising the free cooling potential of the outdoor air in a mechanical ventilation system compared to a mechanical cooling solution might become very limited. These limitations do not apply to the same extent when the outdoor air cooling potential is applied to a free-running building (naturally ventilated building).