Demand-controlled ventilation: an outline of assessment methods and simulation tools

Enhancing the energy efficiency of buildings imposed by global warming and by the perspective of fossil fuel dwindling requires new technical solutions, more efficient. The race for efficiency directly affects ventilation and air tightness of buildings, the main potential causes of heat loss in homes. If heat recovery is emerging as an effective solution to meet energy performance and indoor air quality in climates with harsh winters, some other solutions appear to be very efficient in moderate climates. The unbalanced demand-controlled ventilation, by adjusting the airflow as to the needs, provides a particularly effective alternative to heat recovery on climatic zones where the difference in indoor-outdoor temperature may not be enough to balance the excess power consumption generated by the heat recovery. Used with humidity control (automatic control of the airflow according to humidity level through a mechanical sensor), unbalanced demand-controlled ventilation system has met a large success due to its simplicity of implementation and operation, especially in the field of social housing where the investment and maintenance constraints are often dominant. Born in France in the early eighties already in a context of an energy crisis, humidity controlled ventilation has since spread to various countries where it now benefits from a real technical assessment in the regulation. This is particularly the case in Belgium, Spain, Germany and Poland. Different evaluation methods, different tools and assumptions are used according to countries, leading to substantially different results from one country to another. This variety of performance, whether on the energy side or IAQ, finds its origins in various parameters such as regulated airflow rate for reference, outdoor climate, and occupancy modes. This article aims to provide a state of the art of simulation tools, assumptions and evaluation procedure used in different countries to assess DCV. Reference to several studies complement this presentation, such as that conducted by the Fraunhofer Institute in 2009 to compare heat recovery and unbalanced demand-controlled ventilation or the one by Air.H in 2009 to assess the reliability of the simulation tool used in France. This software has been directly compared with actual measurements made on site during a large-scale monitoring in Paris (2007-2009), with very convincing results on the relevance of the calculation algorithm and on the assumptions. Several tools such as SIREN from CSTB, CONTAM from NIST and WUFi® from Fraunhofer IBP have proven their reliability to assess DCV. Various evaluation methods are now used in different countries, moving DCV and humidity controlled ventilation from innovative to standard. The availability of simulation tools and assessment methods remains essential for all countries wishing to exploit the energy gain potential offered by this technology