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For zero and low energy buildings, high-energy efficiency ventilation is very often confused with a complex mechanical ventilation system with heat recovery. In school gymnasiums, where large volumes have to be ventilated, and where intermittent occupation is very usual, demand controlled natural ventilation has several advantages, making this technique very attractive. High stack height makes natural ventilation very efficient, limiting the necessary number and dimensions of windows.

Ventilation in low energy refurbished buildings is the cause of a big part of energy losses. In order to reduce this impact, some energy regulations prescribe a solution (such as the Swiss energy Law, prescribing heat recovery) and others prescribe a system global performance (such as the EU delegated regulations No 1254 and 1253 /  2004 determining a global energy performance label of the ventilation system).

In response to the European Energy Performance Buildings Directive 2010/31/EU and the Energy Efficiency Directive 2012/27/EU, buildings have increasingly become more insulated in order to reduce the heating losses to a minimum. However, this could also lead to the problem of indoor high temperatures during warm and transition seasons. Furthermore, the Intergovernmental Panel on Climate Change (IPCC) warns about increases in temperature of more than 4 ºC by the end of the century.

Because of the customer need of best possible comfort condition and satisfaction, shopping centers are conditioned by means of basic HVAC systems, often without considering the potential of natural ventilation to contribute to air change rate, and to reduce the cooling demand. Mechanical ventilation systems are also preferred to natural ventilation because more controllable and reliable since they are not affected by the uncertainty of natural forces.

New buildings have to satisfy ever-tightening standards regarding energy efficiency and consumption. This results in higher insulation levels and lower air leakages that reduce heating demands. However, even at moderate outdoor temperatures these buildings are easily warmed up to such a degree that in order to ensure acceptable indoor environment quality, removal of excess heat becomes unavoidable. Use of electric energy related to mechanical cooling is considered incompatible with achieving zero energy buildings (ZEB).

EU energy policy encourages member states and public authorities to start converting building stock into nearly Zero Energy Buildings (nZEB) and adopting exemplary actions. ZEMedS project focuses on the issues related to the refurbishment of schools to nearly Zero Energy Buildings (nZEB) in France, Greece, Italy and Spain. Presently, there is a gap in national regulation of Mediterranean countries to embody the 2012/27 EED as far as renovation rates of public buildings are concerned.

From the energy point of view, buildings should be as tight as possible. But lack of ventilation will result in high level of indoor pollutants, which is harmful for occupants. Numerous studies find that lack of ventilation could cause symptoms for occupants, which are characterized by World Health Organization as Sick Building Syndrome.

Hemp Lime concrete (HLC) is a bio-based material, which knows currently a growing development. HLC is a low embodied energy material. It has an excellent moisture buffer performance and is considered as good indoor climate regulators. Recent field study has confirmed the ability of HLC to maintain hygrothermal conditions at winter and summer comfort levels.  

The differences between extract ventilation and balanced ventilation are subject of many discussions in sales markets where both solutions have their share. Often, the differences are marked in terms of energy, because balanced ventilation is normally accompanied by heat recovery. But there is another difference in terms of the ventilation effectiveness of the system.This document reports experiments in a scale model of a house showing the difference between extract ventilation and balanced ventilation in ventilation effectiveness, and therefore in achievable indoor air quality.

The long term exposure to fine particulate matter with a diameter of ≤2.5 μm (PM2.5) is linked to numerous health problems, including chronic respiratory and cardiovascular diseases, and cancer. In dwellings, a primary emission source of PM2.5 is cooking, an activity conducted several times per day in most households. People spend over 90% of their time indoors and more time in their homes than any other type of building. Therefore, they are at risk of exposure to elevated levels of PM2.5 emitted by cooking if these particles are not removed at source.