Domestic Ventilation System Research Articles

Ventilation regulations and occupant practices: undetectable pollution and invisible extraction

This sociotechnical investigation examines the use of ventilation systems in homes in London, UK. These homes were built with ventilation systems as described by guidance in the UK Building Regulations Approved Document F. These systems are assumed to provide adequate ventilation rates. However, previous measurements in these homes show that ventilation rates are inadequate. Using social practice theory as a framework to analyse the qualitative data, the intended use of the ventilation systems is compared to participants’ actual practices of manipulating the indoor air, revealing discrepancies between the two. Occupants had limited knowledge of indoor pollutants but were highly motivated to control and interact with the smells and air in their homes. They primarily used technologies that were not part of the planned system, because the latter’s functioning was opaque to occupants and not well connected to their other practices. The highlighted discrepancies in four case study homes between planned and actual ventilation system operation help to identify how future systems could be improved to ensure adequate ventilation rates and good indoor air quality in airtight homes. Policy relevance This research investigates the extent to which the intended operation of domestic ventilation systems set out in Approved Document F to the UK Building Regulations is accomplished in practice. The findings show that ventilation equipment is not used as intended. The research suggests a need for future guidance to more actively consider routes by which occupants can learn how to use and maintain their ventilation systems, and how to identify and remove indoor air pollution. There is a risk of continuing underventilation in homes unless efforts are made to ensure the systems are easily interpretable and robust to a reasonable range of internal conditions and social contexts.

공동주택 열회수환기장치의 미세먼지 필터링 성능 개선을 위한 프리필터 시스템 개발

Due to particulate matter of air, most occupants rely on air cleaners. However, when indoor air quality is managed by air cleaner only without opening the windows, the chemical suspended substances are not removed, which affects the health of occupants. On the other hand, the mechanical ventilation system in which the air supply or exhaust by fan is installed near the outer wall of the building so that the indoor air can be forcibly discharged or the required ventilation amount can be accurately supplied. Therefore, indoor air quality is maintained by diluting the concentrations of volatile organic compounds and carbon dioxide that air purifiers can not remove. However, the domestic ventilation system has a structural defects than the high efficiency and high performance ventilation system. In terms of particulate matter inflow, the problem is that the airtightness of the device is low. In addition, through the building ventilation system and domestic distribution filter investigation, it was confirmed that most of the filtering configuration is similar to one general nonwoven filter. Therefore, this study suggests a “Pre-filter System” which can be installed in the ventilation system to enhance the usability and particulate matter filtering performance of the existing ventilation system.

How loud is too loud? noise from domestic mechanical ventilation systems

Noise from domestic ventilation systems is currently a little understood problem in the UK. Other European countries that have a longer history of using mechanical domestic ventilation systems have introduced noise limits for these systems. Without mandatory limits for noise in UK, noise is not a factor that is often considered during the design. However, noise can be a significant constraint to the use of ventilation systems. Research is reviewed from across Europe and North America which indicates residents turn off ventilation equipment that has objectionable noise. Without adequate ventilation in modern airtight dwellings, poor air quality can have a significantly adverse effect on the health of the occupants. There is a lack of evidence in the literature and performance standards for appropriate noise metrics and values that occupants find acceptable: this research is urgently required, and the steps to realise this are outlined; interim noise limits are proposed. Causes of excessive noise are found to originate due to problems during the design, procurement, installation, commissioning and operation of ventilation systems. A suitable metric is required along with regulatory control to ensure that residents are not forced to choose between intolerable noise or inadequate air quality.

Lack of pro-active technology in indoor air quality protection

Indoor air quality (IAQ) influences the health of humans, the young and the old being generally more susceptible. Indoor air, the air that we breathe more than 80% of the time, is increasingly pre-treated or arriving through filters and ducts. Any technological solution for ventilation should pro-actively protect IAQ, by improving or not deteriorating the quality of outdoor air coming in, and alarming when IAQ levels are declining. In this study we examined how human IAQ needs are met, in design or in practice, by domestic ventilation systems, including natural ventilation, balanced ventilation, and adaptive systems. Methods Three population groups with different sensitivity towards air quality were recognized: healthy adults (between 20 and 49 years of age), healthy younger and older persons, and chronic lung sufferers. Risk aspects of ventilation systems were identified from literature: pollution accumulation, draught, and maintenance. Current indoor air quality in Dutch dwellings was evaluated from continuously measuring 4 indoor air quality indicators (CO2, humidity class, ventilation rate, and fine particles) in 37 dwellings for a whole week in winter each. Ventilation was by windows and grids, or grids and exhaust fans. Actual IAQ levels in dwellings were linked to complaint percentages in different air qualities derived from literature. Results The size of the groups with moderate (young, old) and high (lung sufferers) sensitivity is large and increasing, both in relative and absolute figures. An acceptable IAQ for the most susceptible group was not present in any of the dwellings, whilst only one dwelling met the standards for the group of young and older persons. Most common cause was inadequate ventilation. Newer systems with balanced ventilation have intrinsic risks with regard to maintenance (filters) and cleaning (ducts). Intelligent adaptive systems with mechanical exhaust only are in theory the best choice to protect IAQ. Discussion A healthy design of a ventilation system should include flexibility in supplied airflow (both a secure base level around the clock, and a high on-demand level) and an excellent removal of accumulated dirt on the surfaces of the ventilation system at the inlet side. Newer systems with adaptive features should be checked further in practice. Pro-actively protecting IAQ in dwellings through adaptive sensor-controlled ventilation systems may be a way to avoid health risks from indoor air for the elderly and other susceptible populations.

The Effect of Sorption on Airborne Moisture Movement in Dwellings

A Moisture Admittance Model, which takes into account absorption and desorption, has been developed to simulate moisture behaviour in dwellings. The model has been integrated with the BREEZE computer model used to simulate air and contaminant flow. Simulations from the combined model have been compared with predictions using the Louden model and with measurements of vapour pressure taken in a test house. The Louden model tended to over-predict experimental values but there was reasonable agreement between the MAM-BREEZE model results and measured values.The effect of sorption on the performance of a domestic ventilation system was also investigated. The Lounden model, which does not take sorption into account, can over-estimate humidity peaks. The use of such a model in the design of a ventilation system could result in over-ventilation and reduced energy efficiency.

Air flows in dwellings—simulations and measurements

A study of the reliability of systems by considering the ability of different systems to maintain a required air flow rate over time is included in a subtask of IEA Annex 27 `Evaluation and Demonstration of Domestic Ventilation Systems'. Measurements and calculations were performed to determine the variation in ventilation rates due to variation in climate and variation in performance of the ventilation system. Dwellings with passive stack, mechanical exhaust and mechanical exhaust-supply ventilation, representative of the Swedish housing stock, were studied. Diagnostic tests were carried out, to discover if the installed ventilation system was functioning as designed e.g. air flows in mechanical ventilation systems and to determine certain values e.g. airtightness. The continuous monitoring included tracer gas measurements in dwellings of overall and local (individual rooms) ventilation rates, and measurements of boundary conditions, during three different periods, each lasting 1–6 days. Predictions of air flows were made for the measuring periods using COMIS, a multi-zone network model. This article presents and discusses the measurements and the calculations and compares the two. The predicted and measured average total outdoor air ventilation rates agree reasonably well. The agreement is less good for individual rooms.

IEA annex 27: Evaluation and demonstration of domestic ventilation systems. Assessments on noise

The acceptance and appreciation of ventilation systems is mainly determined by the perceived indoor air quality, thermal comfort and noise. Noise in relation to ventilation systems can be divided into three categories: (1) outdoor noise (entering the dwelling through ventilation openings, cracks, mechanical supply and exhaust openings, etc.); (2) noise generated by components of the ventilation system and; (3) the impact of ventilation systems on sound reduction of partitions (between dwellings, rooms, etc.). Depending on the type of ventilation system, one or more of these aspects are of concern. Noise related to the ventilation system and components, can result in turning off the ventilation system or closing vents, etc. This can have a negative influence on ventilation and indoor air quality. In the framework of IEA ANNEX 27, several noise aspects of domestic ventilation systems have been evaluated. Outdoor noise: In noise loaded areas, the selection and the applicability of different types of ventilation systems are determined by the noise level on the facades. A simplified tool is developed to select ventilation systems as a function of the required noise reduction of the facade, room dimensions and design and construction of the facade. System noise: Controlling noise levels caused by ventilation systems is in practice one of the most important factors to contribute to the satisfaction with a ventilation system. Air duct systems in dwellings transport noise generated by fans and aerodynamic noise generated by bends, control valves, grilles, etc. ANNEX 27 gives basic equations to estimate sound power levels of fans and grilles, indication of sizes for silencers and guidelines for design. Impact on noise reduction of partitions: The composite sound reduction is the result of different sound channels from one room to the other. One of this sound channels may be the ventilation system (cross-talk). Cross-talk can be brought about through the air duct system, overflow grilles and ventilation openings in partitions, duct transitions, etc. ANNEX 27 provides guidelines for sound reductions of partitions and insertion losses for ducts to eliminate the influence of cross-talk.

Domestic ventilation with heat recovery to improve indoor air quality

Recently in the U.K., and particularly in Scotland, domestic ventilation systems have been considered as means of reducing condensation in existing housing stock. A simple ventilation model which is suitable for ventilation systems with a heat recovery unit is presented. Using field data of temperature and relative humidity, air supply and extract rates for individual rooms are estimated by applying this model. Unlike conventional systems, extract from bedrooms is considered necessary for the type of dwellings considered to reduce surface condensation.