Evaluation of a prescriptive ventilation standard with regard to 3 different performance indicators

In this paper, the performance of Belgian building code compliant residential ventilation systems is evaluated on multiple performance indicators: occupant exposure to bio-effluents, occupant exposure to other use-related pollutants (odours) and occupant exposure to building material emissions. The fitness of the proposed criteria in this context is then discussed in a broader context and this information is then used to interpret the fitness of the code prescriptions as design criteria for performant ventilation systems

A simple airlfow path approach to sizing natural ventilation systems in a code context

Most of the existing ventilation standards are drafted in a rather prescriptive way. Growing focus on the implementation of rational energy use however, introduces an urgent need for more performance-based criteria. Optimization of energy consumption obviously encompasses minimization of ventilation airflow rates. Comfort, on the other hand, should not be reduced because of these actions. To implement this in a legal figure, one can appeal to the principle of equivalence. This principle states that all systems achieving equivalent performance to that of the systems described in the standard are acceptable. Better yet, a new standard can be devised, imposing a reference performance rather than a reference system. This avoids all discussion about the way the reference system’s performance should be interpreted. Nevertheless, practical implementation of a standard will require the definition of sizing guidelines for design purposes. The method presented in this paper is a simplified approximation of the airflow network in a building. It is conceived as a sizing guideline for natural ventilation systems in the context of a national ventilation standard. Supply, internal and exhaust resistances are the main parameters, next to overall building airtightness. These parameters are system independent and allow to describe a large scale of possible buildings. Five different dwellings, with different typologies, representative for the Flemish building stock, were evaluated for this purpose. The predicted airflow and indoor air quality are compared to that predicted by a detailed multi-zone model and acceptable agreement is found. This yields the conclusion that, for the implementation of a performance-based ventilation standard, straight forward calculation methods for sizing guidelines can be incorporated in the standard

Analysis of the influence of ventilation rate on sleep pattern

In this paper, the results from a field study on the influence of ventilation rate on the sleep pattern are presented. The testgroup was asked to sleep in their normal sleeping environment (student dorms) in order to cause as little disruption in the normal pattern as possible. For the same reason, actigraphy was used to measure sleep patterns since this is one of the least disturbing measurement techniques available. The student dorms were selected as a location because all rooms are identical and basic conditions are therefore very similar for all the participants in the study. The participants were also asked to fill out a number of questionnaires to determine their general attitude towards sleep and to get an idea of their subjective appreciation of the sleep quality experienced over the test period. The results show only a very small effect of the ventilation rate on the sleep pattern

Passive house ventilation strategies: demand control?

Since insulation levels in a passive house context are very high, energy losses trough ventilation are of relatively high importance in the total energy balance of a passive house concept. Although fully mechanical ventilation systems are at the core of the this concept, enabling both regeneration and cheap space heating, it can still be optimized. With demand controlled systems, excess ventilation can be minimized, thus reducing both redundant ventilation losses and the accompanying electrical loads. This paper reviews the possibilities for a performance based optimization of ventilation systems for passive houses within the context of the Belgian legislatio

Bedroom indoor air comfort : a critical analysis

The criteria that are currently used for the assessment of Indoor Air Quality in a residential context were developed in the ‘80s and relate to comfort during occupancy. More than half the time at home however, is spent in the bedroom. There is no strong indication that the criteria that are traditionally used to assess Indoor Air Quality also relate to the level of comfort while asleep. Moreover, analysis of the results of a performance assessment of frequently used residential ventilation systems based on these traditional criteria, shows that they are dominated by the pollution level in the bedrooms

Convective Heat Transfer coefficients in mechanical night ventilation: a sensitivity analysis

Since the Energy Performance for Buildings Directive (EPBD) was accepted and implemented over the course of the last years, buildings are audited energetically to receive the necessary construction licenses. This augmented the already high attention to research on innovative (passive) energy-saving system concepts even further. Previous research suggests that, although the effect of commissioning can be significant, specific fan power is the most important factor influencing the energetic viability of mechanically driven night ventilation as an active cooling replacement. This parameter should thus be the central point of focus during the design process. In this paper, we present an analysis of the effect of detailed convective heat transfer modeling on the predicted performance, in order to determine the level of detail needed to assess feasibility of this kind of system in early design phases. Results indicate that the effect amounts to 20-50% of the predicted performance and therefore cannot be neglected. It is within the range of effect of the dominant parameter, specific fan power. In light of these results, it is suggested that detailed convective heat transfer coefficient modeling is taken into account whenever forced convection due to large volume flow is introduced

Overcoming condensation problems in a closed cavity double skin façade

For highrise office buildings, double skin façades offer a attractive alternative in building envelope conception. A recurrent problem in concepts with single outdoor and double indoor glazing (“passive façade”) is condensation on the cavity side of the single glass pane. Permasteelisa Group developed a innovative concept, employing a fully sealed cavity and a very modest dry air flow (“closed cavity façade”), that prevents condensation at all times, thus preventing dirt offset on the window panes and eliminating the need for cleaning inside the cavity over the lifetime of the façade. This paper presents a coupled multizone airflow / thermal model developed to assess condensation risk inside the cavity under different climate conditions and the initial validation. Additional validation experiments are held in the 2008-2009 winter season. This model is now implemented as a R&D tool and to size the system components in actual projects

Performance assessment of demand controlled ventilation controls concerning indoor VOC exposure based on a dynamic VOC emission model

The performance assessment of ventilation systems often focusses only on CO2 and humidity levels. The indoor Volatile Organic Compounds (VOC) emissions of building materials or other products is thereby overlooked. The new generation of ventilation systems, Demand Controlled Ventilation (DCV), are systems that do not supply the nominal airflow continuously but are controlled by CO2 or humidity sensors in order to save energy. This poses potential problems for exposure to VOCs. In this study, a dynamic VOC model, which takes into account changing temperature and humidity that was derived from literature, is implemented in a CONTAM model of the Belgian reference apartment. The impact of a DCV system on the indoor VOC levels is investigated. Results show that the use of a dynamic model is necessary compared to the previously used approximation of a constant emission. Furthermore, on a system level, the influence of the ventilation system control on the indoor VOC levels shows. The overall VOC concentration in the different rooms will be higher because of lowered ventilation rates. Especially in rooms that are often unoccupied during the day, the accumulation of VOCs shows. In the development of DCV system controls, the aspect of VOC exposure should not be overlooked to be able to benefit from both the energy savings and improved Indoor Air Quality (IAQ)

Performance of natural, exhaust, demand controlled exhaust and heat recovery residential ventilation systems as prescribed by the standards in 5 European countries

Over the last decades, residential ventilation standards have been integrated in most of the buildings codes of European countries. Contrarily to the consolidation effort in the development of the nonresidential ventilation standard EN 13779, most of the residential ventilation standards have been drafted in a prescriptive way, with disparate sizing prescriptions in the different countries. Due to these differences in ventilation requirements, the reference levels for ventilation heat loss and associated indoor air quality is different in each country. The energy saving potential for demand controlled systems is therefore different in each country as well. In this paper, the performance of natural, exhaust and mechanical residential ventilation as prescribed by the standards of 5 European countries with moderate climate is assessed with regard to perceived air quality and odour spread as well as heating season integrated ventilation heat loss using multi zone simulations with local climate data. These results are then used to calculate the energy saving potential of a demand controlled exhaust ventilation system based taking into account the trade-off between indoor air quality and heat loss. With results showing that about 50% of ventilation heat loss reductions can be achieved at equivalent indoor air quality levels, we conclude that demand controlled exhaust ventilation has a good potential for reduction of building energy use in moderate climates

Impact of an occupancy and activity based window use model on the prediction of the residential energy use and thermal comfort

The opening of windows can lead to high energy losses in wintertime, especially in nearly zero-energy buildings. But can reduce overheating significantly in summertime. Therefore, window use models have been created in the past to assess the energy use and thermal comfort in residential buildings. The models are mostly based on weather-variables. However, a recent study (Verbruggen, Janssens, et al. 2018) indicated that these models were not able to accurately predict the window use in wintertime. For that reason, an occupancy and activity based model was developed. In this article, the impact of the application of the new window opening model on the residential energy use and thermal comfort was assessed. The object-oriented modelling language Modelica was used to simulate the energy use and temperatures in a nearly-zero energy house, which is a representation of an existing house in a nearly zero-energy neighbourhood in Kortrijk. From this neighbourhood, measured energy use data was available as well as window sensor data for some of the houses. These measured data were compared to the simulated data of the new window use model, a weather-based model and the Belgian EPBD-calculation method. The occupancy and activity based model could predict more accurately the average opening durations in wintertime and could better account for the large variation in window use compared to weather-based models. An optimal window opening strategy could limit the overheating significantly, even prevent it in the bedrooms and bathroom. However, opening the windows also implies an increase in energy use for heating. Some combinations of different window opening habits can limit the overheating, while limiting the increase in energy use at the same time