> Low Allergen Building Design

What are allergens?

Allergens are substances that cause an allergic reaction by the immune system. Symptoms often include: headaches, shortness of breath, eczema, sneezing, watery eyes, depression, fatigue, diarrhea, palpitations, coughing, sleeping difficulties, sore throat, dizziness and asthma. In the last fifty years there has been a global pandemic of allergies such as asthma, and its getting worse every year. Current research has linked these reactions to an increase in allergens found with modern building methods and materials. There is now a movement to address these issues within the building industry known as low allergen design or low allergy housing.

Indoor allergens have been identified as dust mites, moulds and fungal spores, fine particles, fumes and gases, and volatile organic compounds (VOCs). VOCs are chemicals that evaporate at room temperature, and many are known to be toxic and hazardous to human health. The building industry has changed radically in the last part of the twentieth century, and indoor allergens are now prevalent in the modern home. Synthetic and chemical products that contain VCOs are increasingly used, and houses are often built to an airtight design using water resistant materials. This has resulted in warm, damp and poorly ventilated spaces, which are the ideal conditions for dust mites, moulds and fungal spores to thrive.

Low allergen design is a whole building approach that aims to reduce and avoid all known allergens, and to minimize the conditions in which they occur. The main areas that are considered in this process are: the specification of materials, ventilation, humidity and heating.

1. Specification of Materials

Many modern building materials contain toxic chemicals and VOCs. For instance adhesives, treated timbers, wood composites, paints, varnishes, carpets, plastics, PVC, furnishings and fabrics all give off emissions that can trigger an allergic reaction. Low allergen design aims to avoid these products and where possible use green specification materials that have zero or low emissions such as:

•  non-toxic paints,
• compressed chipboard (no glues) and,
• natural earth plasters

 Carpets are also to be avoided as they can become breeding grounds for mites and mold. Flooring should be instead constructed with wood, ceramic tiles, concrete or possibly linoleum.

2. Ventilation and Humidity

A good ventilation strategy is essential for an allergen free home. This is partially addressed by using natural building materials such as lime plaster, timber, clay and natural paints which allow a building to breathe. This not only helps to control indoor humidity but helps in preventing VOC build up. An open building design will help with ventilation; as well as the appropriate placing of windows with trickle vents and the placing of extraction fans in high humidity areas (such as kitchens and bathrooms).

A relatively new ventilation method under development is dynamic insulation, this controls ventilation through creating a permeable insulating layer in the walls or ceilings, and uses a wind-driven extraction fan to create pressure between the outside and inside air. Air is drawn into the building from the outside and recovers the heat that would normally been lost to the outside by conduction. Moisture is also conducted out of the building, and in this way both low humidity and temperature regulation is maintained inside.

3. Heating

Low allergen design avoids heating systems which use combustion gases, because this increases the risk of developing an allergic reaction. Heating is instead provided by the use of electricity supplied from renewable energies such as solar and wind; and also through passive solar design. Heating could also be supplied using geothermal energy.

Conclusion

Low allergen design is a holistic approach to creating healthy living spaces. It is a sensitive and intelligent approach to minimizing allergen triggers by combining appropriate green building materials (which are environmentally safe and non-toxic), with design methodologies such as breathing walls and open, well-aired rooms. Low allergen design is a return to a more natural and sustainable way of building, in that both interior and exterior environments benefit, with a positive impact on health.

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