In our Healthy Materials Series, WLLW delves into the properties of the materials we use in our homes to highlight the importance of incorporating those which are healthy, sustainable and contribute to our wellbeing. These materials help improve indoor air quality by reducing exposure to harmful chemicals and pollutants. Additionally, sustainable materials generally have a lower environmental impact, using fewer resources and generating less waste. Choosing healthy and sustainable materials promotes a better living environment, supports ecological balance and provides long-term benefits for both the homeowner and the planet.

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In the first installment of this series we will examine the properties of cork. In use since antiquity, cork is a versatile and environmentally friendly material with a range of potential applications in the home. Originating from the bark of cork oak trees, primarily found in the Mediterranean region, cork is harvested through a process that does not harm the tree, allowing it to regenerate and be harvested repeatedly over its lifespan. Cork is used in a myriad of ways in the home, from flooring and wall tiles to acoustic insulation and decorative accessories. So why is it a healthy, sustainable material?

Health Impact

Cork is naturally resistant to mold, mildew and pests, which helps reduce allergens in the home. It does not absorb dust, so is ideal for use by people who suffer from allergies or asthma. Cork also emits low levels of Volatile Organic Compounds (VOCs), which can cause health complaints such as respiratory irritation, eye and skin irritation, headaches, dizziness and fatigue. Using cork, therefore, can improve indoor air quality compared to some synthetic materials.

Environmental Impact

Cork oak forests play a crucial role in carbon sequestration, absorbing CO2 from the atmosphere, and the cork products themselves continue to store carbon throughout their life cycle. These forests support a rich biodiversity, providing habitats for various species, and sustainable management of cork harvesting helps protect these ecosystems. Additionally, cork is recyclable and biodegradable, meaning that at the end of its useful life, it can be recycled or will decompose naturally without releasing harmful substances.

Pros

• Cork is an environmentally friendly choice, as it supports sustainable forestry practices and contributes to carbon sequestration.

• Cork has excellent thermal and acoustic insulating properties. It helps maintain a comfortable indoor temperature, reducing energy costs, and dampens sound.

• Cork is resilient and can recover well from minor dents and scratches, making it a good option for areas with light to moderate foot traffic.

• Cork is naturally resistant to mold, mildew and dust mites, which can help reduce allergens in the home. This is particularly beneficial for people with allergies or asthma.

• Cork is free from harmful chemicals and VOCs, contributing to a healthier indoor environment.

Cons

• Cork can be sensitive to moisture, which may cause it to expand or warp. It is not recommended for use in areas with high humidity or where it may be exposed to standing water.

• Cork requires regular maintenance to keep it in good condition. This includes cleaning with appropriate products and resealing periodically to maintain its protective finish and durability.

• Cork products can be more expensive upfront compared to some other flooring or wall covering options. However, the cost can be justified by its environmental benefits and long-term durability if properly maintained.

• Proper installation is crucial for cork products to perform well. Poor installation can lead to gaps, warping, or reduced lifespan, so professional installation is often recommended.

Typical Finishes, Dyes and Adhesives

Adhesives for cork installations range from solvent-based types, which can release significant VOCs and potentially cause respiratory irritation and other health issues, to water-based and natural adhesives that are lower in VOCs and safer for indoor environments. Common finishes of cork products include polyurethane, which provides durability and water resistance but can emit VOCs during application and curing. The primary health concerns with these materials stem from VOC emissions, which can cause short-term symptoms like irritation and headaches, and long-term exposure risks including respiratory issues and increased cancer risk.

Terms to Avoid

Terms like ‘composite’ or ‘engineered’ may suggest the presence of additional materials, such as resins or synthetic fillers, which can increase VOC emissions. ‘Vinyl-coated’ cork products, while offering durability and water resistance, often contain vinyl, a synthetic material that can emit VOCs and affect indoor air quality.

Practical Tips

Choose FSC (Forest Stewardship Council) certified cork which guarantees that the product has been made from sustainably managed forests. Water-based sealants, as opposed to solvent-based ones, typically have lower VOC levels and are safer for indoor air quality. Low-VOC polyurethane sealants are available and are a healthier choice for indoor use. Look for certifications such as Greenguard or EcoLogo when selecting sealant products.

Photography: Deyan Georgiev/Adobe, ah_fotobox/Adobe, Clayton & Little by Nick Simonite, Lorenzo Zandri, Pretziada by Claudia Ferril, Gurea Arquitectura Cooperativa