English

The field research project MONICAIR indicates that ventilation systems that fully comply with Dutch building codes show large differences in their IAQ-performance in habitable rooms during heating season and do not always achieve acceptable IAQ-levels [lit.1]. The results indicate that there are considerable differences in the actually achieved air-exchange rates per person during presence in habitable rooms. System averages on CO2-excess doses per heating season (an indicator for the duration and the amount of the excess above 1200 ppm CO2) vary from 68 to 349 kppmh per person.

Ventilation’s historical goal has been to ensure sufficient air change rates in buildings from a hygienic point of view. Regarding its potential impact on energy consumption, ventilation is being reconsidered today. An important challenge for low energy buildings lies in the need to master airflows through the building envelope. Data collected from controls in 1287 recent dwellings shows us that 68 % of the dwellings don't respect the French airing regulation.

Indoor environmental quality (IEQ) is generally taken to encompass four main factors: indoor air quality (IAQ), thermal conditions, visual quality, and acoustical quality. Although there is an implicit concern for safety, the predominant metrics all four in standards for design of buildings are based on perceived quality or comfort.

It is well known, that energy consumed by the HVAC systems in buildings represents an important part of the global energy consumed in Europe (Directive 2010/31/EU). Latent heat storage has been widely studied (Cabeza et al. 2011, Zhou et al. 2012) for its potential in many applications for building energy management (Lim et al. 2014). Passive implementation of phase change materials (PCM) in buildings has demonstrated significant energy reduction of HVAC systems, but with some limitations (Castell et al. 2010). For this reason, active implementation of PCM in buildings has high potential.

The aim of this study is to analyse the behaviour of natural ventilation techniques in low-rise commercial buildings in terms of Indoor Air Quality (IAQ).

Nowadays, important efforts are deployed to reduce energy consumption in the field of residential buildings. Concerning new constructions, low-energy consumption buildings such as “passive” houses constitute a suitable solution to decrease the environmental impacts.In this kind of building, air tightness is improved and heating needs are reduced compared to traditional constructions. In order to ensure a good indoor air quality, controlled mechanical ventilation is required.

Controlling indoor humidity is important in homes, because high indoor humidity is associated with occupant health and building durability issues. Ventilation is often used to avoid peaks of moisture in homes, such as in kitchens and bathrooms. However, in hot-humid climates, outdoor air can have higher humidity than indoors, and continuous whole house ventilation can lead to increases in indoor humidity levels.

In determining ventilation rates, it is often necessary to combine naturally-driven ventilation, such as infiltration, with mechanical systems. Modern calculation methods are sufficiently powerful that this can be done from first principles with time varying flows, but for some purposes simplified methods of combining the mechanical and natural ventilation are required—we call this “superposition”. An example of superposition would be ventilation standards that may pre-calculate some quantities within the body of the standard.

In this study the performance of a residential demand controlled (DC) extract ventilation system with an air-to-water heat pump was analysed via dynamic simulations. A real life test case was setup to validate results. The ventilation system controls automatically the extract air in functional as well as habitable rooms, ensuring indoor air quality (IAQ). The total extract rate is mixed with outdoor air as heat source of the air-to-water heat pump (2.5 kW at standard reference conditions). Domestic hot water (DHW) as well as space heating (SH) can be alternatively supplied.

Demand controlled ventilation (DCV) can reduce the energy use significantly compared to a constant air volume (CAV) system. However, there is still a large uncertainty about the real energy savings and the ventilation efficiency. Furthermore, control and operation of the system are more complex. To formulate answers to these questions, measurements on a DCV system in a university building in Ghent, Belgium provide insight in the system operation and performance and the air distribution in the classrooms. Monitoring is carried out in March and May 2015.