Allergens are substances that cause an allergic reaction in the immune system. Symptoms include: headaches, shortness of breath, eczema, sneezing, watery eyes, depression, fatigue, diarrhoea, 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, a situation that is getting worse every year. Current research has linked this to an increase in allergens associated 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 minimise the conditions in which they occur. The main areas that are considered in this design process are: specification of materials, ventilation, humidity and heating.
Specification of Materials
Many modern building materials contain toxic chemicals and VOCs. 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 wherever possible uses 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 avoided as they can easily become breeding grounds for mites and moulds. Flooring is instead constructed with wood, ceramic tiles or sometimes linoleum.
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 that allow a building to breathe. This not only helps to control indoor humidity but also helps to prevent VOC build up. An open building design will help with ventilation, as well as appropriate placing of windows with trickle vents and placing extraction fans in high humidity areas such as kitchens and bathrooms.
A relatively new ventilation method being developed 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 have 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 the building.
Low allergen design avoids heating systems that use combustion gases, because gas significantly increases the risk of developing an allergic reaction. Heating is instead addressed through the use of electricity supplied by renewable energies such as solar and wind, and also through the use of passive solar design. Heating can also be supplied using geothermal energy.
Healthy Living Spaces
Given that around one in four people in the UK now have asthma and that we spend most of our time indoors, it is imperative that every effort be made to eliminate all known and suspected indoor allergens. Building regulations need to be changed to protect and secure people’s health, and also to protect the industry from the threat of litigation, since increasing numbers of legal cases are being brought against builders, landlords, housing associations and insurers over health problems associated with indoor allergens.
Low allergen design is a holistic solution for creating healthy living spaces. It is a sensitive and intelligent approach to minimising 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 marks a return to a more natural and sustainable way of building, such that both interior and exterior environments will benefit, with a positive impact on human health.