The Okohaus : Referenced as Case Study 7.9 An Alternative Business Premises Architects Sambeth and Eble 1992 Photo: Sandy Halliday Author: Sustainable Construction 2nd Edition

Building-related ill-health solutions. Science.

Photo: The okohaus : Referenced as Case Study 7.9 An Alternative Business Premises. Architects Sambeth and Eble.

Creating good indoor environment quality is vital to health and well-being. Elimination of pollution at source and good ventilation is fundamental to maintaining quality of life for everyone.

Author: Professor Engineering Sandy Halliday. Sustainable Construction 2^nd Edition.

This is particularly true for the most vulnerable who spend more time indoors and also may have less ability to manage their environment or to communicate discomfort.

Internal environments are known to have higher concentrations of pollutants than external environments.

Building-related ill-health (BRI)

Building-related ill-health (BRI) describes a collective adverse reaction an indoor environment. Once dismissed a psychosomatic, it was identified as a genuine, serious issue in the 1980s associated largely, but not wholly, with tightly controlled and mechanically ventilated (MV) buildings. Symptoms included congested nasal passages, inflamed eyes, palate and pharynx, dry skin, headache, fatigue and attention deficit.

Despite research and correlation with volatile organic compounds (VOCs) and high temperatures, it proved difficult to identify a specific cause or to predict affliction rates. However, the association with VOCs, tight control and MV stuck. Many designers sought solutions in natural ventilation (NV), which also proved difficult, if poorly designed it can introduce external pollution, waste heat and create unacceptable variability in indoor temperature, air movement and humidity.

Emissions from building products

The situation is exacerbated as the materials used in building are a potential source of pollutants and they have undergone perhaps greater changes than any other aspect of construction.

At the beginning of the twentieth century, about 50 materials were used in buildings. Now, more than 70,000 are available and most are man-made. There has also been a dramatic upsurge in the occurrence of synthetic chemicals indoors due to off-gassing from structural components, fixtures, finishes and furnishings, heating equipment and cleaning materials.

Concentrations of more than 35 volatile organic compounds (VOCs), including vinyl chloride, benzene, bisphenol formaldehyde and toluene, are typically ten times higher indoors than outdoors.

Many of these VOCs have been identified as emanating from building products and are associated with a wide range of detrimental health effects in humans and animals (including cancers, tumours, irritation and immune suppression).

The higher the temperature, the more VOCs appear in the gaseous phase. It has also been shown the gaseous concentrations of many VOCs are directly proportional to air humidity (though this is not the case for formaldehyde).

Information is available on sources of VOCs, the extent of emissions, and assessing emission rates and indoor air quality, although avoidance is the best strategy.

Air-conditioning vs Natural Ventilation and Mixed Mode

Studies by Bordass & Leaman compared air-conditioned, assisted NV, mixed mode and NV buildings, and identified that occupant satisfaction was largely independent of the ventilation strategy. It transpired that spaces needed to be better designed with more attention to detail, and simple solutions that are easily understood and controlled by occupants and managed, are preferred.

In recent years hybrid/mixed-mode strategies have become established to combine approaches. They encourage ventilation to be designed on a room-by-room basis to meet the requirements of different users at different times and places within a building.

The ventilation strategy should be thought through from project inception and consider location, occupancy patterns, how spaced will be used, manageability, repair, cleaning, fit-out and control, It influences all aspects of the design. It is important to eliminate avoidable heat gains and pollutants. Windows are crucial, whatever the strategy, because they have to meet a large number of requirements.

The value of investing in a better-quality indoor climate is undisputed – an increase in productivity or reduction in absenteeism by 0,6% of sufficient to justify a 60% increase in expenditure on indoor air quality.

Moisture management

Moisture levels can also affect indoor air quality. Common health complaints, such as asthma, are exacerbated by high and low humidity. Building methods in the last 100 year have sought to address problems of rising damp and moisture ingress. However, a change in materials specification has also had an impact on the heat- and damp-relating capacities of buildings.

Modern materials, for instance, plastic-based paints and finishes tend to be less hygroscopic and offer less buffering of moisture. As understanding of how our skins deals with moisture has increased, design of clothing has tended to more, allowing moisture to escape, and buildings too are being designed to be moisture transfusive.

Thermal mass also has an impact on moisture management. In lightweight buildings, without consideration of moisture management, rapid cooling gives rise to a rapid increase in relative humidity (RH) that is detrimental to both building and occupants.

Hygroscopicity describes the ability of some materials to absorb moisture when humidity rises and emit it when the air becomes dry.

Depending on factors such as insulation, materials, “cold bridges” and air leakages, a building can cope with more or less moisture in the air. Hygroscopic materials stabilise the RH and help prevent dap-related damage. Some porous materials can hold quite large quantities of moisture without any biological activity or degradation. Materials such as timber, plaster, earth and textiles have hygroscopic properties as long as they are not given impervious coatings.

Fluctuating conditions lead to the worst effects of microbial activity. Spaces exposed to sudden changes in moisture loads, including we rooms and schools, may have problems coping with temporary increases in moisture loads. Films of moisture form on non-hygroscopic surfaces and, as nutrients dissolve in the moisture, micro-organisms proliferate As the films dry, they produce spores and release toxins.

Some materials can sustain very large populations of micro-organisms; for example, plastic membranes and glass fibre can have colonies of fungi and bacteria that are 1,000 to 50,000 times greater than natural materials, Thus, if an indoor environment is likely to be subjected to sudden moisture loads, the damp-buffering capacity of materials becomes particularly important for maintain a healthy relative humidity.

Hygroscopic materials versus mechanical ventilation

A valid solution to problems of build-up of moisture in the air is to increase ventilation rates, and increasingly the response has been to mechanically ventilate. However, Finnish research has shown the hygroscopic materials can be more then nine times more effective than mechanical ventilation at dealing with indoor humidity.