Because of several motivators, such as the mitigation of global warming, the reaching of peak oil and health concerns related to fossil fuel burning, contemporary building practise is searching for advanced concepts and technological innovations that will allow to maintain or improve the comfort level that is currently reached while reducing the energy consumption that is related to it. Ventilation is ambiguously related with this energy saving rationale. Since it makes up for about half of the energy consumption in well insulated building, it is an attractive target for energy saving measures. However, simply reducing ventilation rates has unwanted repercussions on the indoor air quality. Two main strategies have been developed to reconcile these seemingly opposing interests, namely heat recovery and demand control ventilation. This paper focuses on the energy saving potential of demand controlled mechanical exhaust ventilation in residences and on the influence such systems may have on the indoor air quality to which the occupants of the dwellings are exposed. The conclusions are based on simulations done with a multi-zone airflow model of a detached house that is statistically representative for the average Belgian dwelling. Several approaches to demand based control are tested and reported. Both energy demand and exposures are reported in comparison with a classic system, operating with continuous flowrates, that is building code compliant. This is necessary to assure that the reported energy saving potential does not derogate the indoor air quality. Within the paper exposure to carbon dioxide and to an odour tracer gas are used as indoor air quality indicators. Monte-Carlo techniques are used to ensure that the reported results are representative for the diverse boundary conditions and parameters that may occur with real life implementation of such a system. Under the conditions that were applied, reductions on the energy demand for ventilation -with the exclusion of adventitious ventilation and infiltration -of 5 to 60% can be reported, depending on the control strategy that is implemented.

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In order to achieve carbon neutrality in the building field as expected by the Energy Performance of Buildings Directive, it is important to not only be able to calculate energy performance during design but also to be able to measure the actual energy performance of buildings during occupancy. However, there is currently no approved methodology for assessing the energy performance of the building envelope of an occupied building independently of its occupants, its systems and the climate. We applied a mathematical method to determine the heat loss coefficient (HLC) of the building envelope, from data collected in occupied buildings. The paper describes the in-situ measurement protocol and the mathematical models that contributes to address this challenge. Our methodology is demonstrated on a new semi-detached house, more insulated than the regulatory level, located in Brussels from a full year of monitoring data. For this case study, the results are promising. Indeed, some mathematical models show results of the same range value for the occupied insitu HLC and the reference HLC, obtained from in-situ measurements but without occupancy. However, more case studies should be evaluated, in order to validate the methodology.