indoor air quality

This paper presents a study of the potential for the use of natural ventilation systems in Portuguese multi-family residential buildings under winter climatic conditions. The behaviour of various natural ventilation systems is tested in a standard residential dwelling, using the TRNSYS 15 and COMIS 3.1 software programs. This study leads to the conclusion that the use of hybrid ventilation systems can save a considerable amount of the energy normally spent on continuously operating mechanical ventilation systems.

As a novel air distribution system, diffuse ceiling ventilation combines the suspended acoustic ceiling with ventilation supply. Due to the low-impulse supply from the large ceiling area, the system does not generate draught when supplying cold air. However, heat sources play an important role on thermal comfort in the occupant zone. Another characteristic of this system is its lower pressure drop compared with conventional ventilation systems, which reduces the noise problem and, at the same time, the energy consumption of the fan can be reduced.

Rehva Guide No 6 – Indoor Climate and Productivity in Offices - states as its main purpose to establish quantitative relationships of indoor environmental aspects with performance and sickness absenteeism. The following relationships were established: temperature with performance, ventilation with performance, perceived indoor air quality with performance and ventilation with sickness absenteeism.

The synergistic effects between summertime ventilation behaviour, indoor temperature and air pollutant concentration in relation to energy retrofit and climate change have been under-investigated to date. This paper explores such interactions in a social housing setting. The case study flat is located on a mid-floor of a high-rise council tower block in central London. Dwellings of this type are likely to be occupied by vulnerable individuals (elderly people or people suffering from ill health or mobility impairment).

Ultraviolet Germicidal Irradiation (UVGI) systems use 254 nm UVC radiation to inactivate microorganisms in the air and on surfaces. In-duct UVGI systems are installed in air-handling units or air distribution systems to inactivate microorganisms “on the fly” and on surfaces.  The literature contains few investigations of the economic performance of UVGI. This study presents a simulation-based life-cycle cost analysis of in-duct UVGI in a hypothetical office building served by VAV systems.

In-duct ultraviolet germicidal irradiation (UVGI) systems treat moving air streams in heating, ventilation, and air-conditioning (HVAC) systems to inactivate airborne microorganisms. UVGI system performance depends on air temperature, velocity, cumulative operating time, variations in exposure time and other factors. Annual simulations of UVGI efficiency and space concentration that accounted for these effects were performed for a hypothetical building served by a VAV system.

The well-mixing assumptions, uniform distributions of air temperatures and contaminant concentrations and neglect of air momentum effects in a zone, used in multizone airflow network models could cause errors in some cases. Through dimensional analysis of the published data from the literature, this study has found correlation between the errors and mixing levels. Our study concluded that the assumption of uniform air temperatures is not appropriate if the  vertical non-dimensional temperature gradient is higher than 0.03.

Calculating contaminant concentrations in or the required ventilation for a space has been a difficult and confusing part in the application of the IAQ Procedure of ANSI/ASHRAE Standard 62.1-2004; Ventilation for Acceptable Indoor Air Quality. Appendix D of ASRAE Standard 62 presents one method for performing these calculations, but it is limited to the steady-state analysis of a single zone. More recently, two software tools have been developed by the United States National Institute of Standards and Technology (NIST) to facilitate these calculations and to include transient effects.

Scientific studies have linked particulate matter with a series of significant health problems. In ventilation systems, indoor particle concentration and dust load on air duct surfaces are two concerns for human health. PROBE-PM (Predicting code for building environment-particulate matter transport simulation), a code to simulate the particle transport in the whole ventilation system is developed.

A new concept, the spatial flow influence factor (SFIF), put forward by us in our previous paper, provides a new insight into the airflow structure. In this paper, several typical illustrative examples are presented to show: (1) how to optimally arrange the chemical pollutant sources and the occupied regions for a given indoor airflow; (2) how to optimize the position of adsorption materials. From the examples,  it is seen that the concept is powerful in the control of indoor air gas pollutants.