What is Lime and Cork Thermal Render?

Lime is a wonderful product for eco-conscious projects. By employing EWI-748 Lime Basecoat, you can install mineral wool insulation systems. However, there is another solution, which is lime and cork thermal render. Lime and cork are both natural materials; therefore, the combination maintains the exceptional benefits that both materials offer. With a new line of products on the horizon for the Heritage Lime Range, this blog will discuss the role and benefits of each material and how they work together.

Natural benefits of lime

Lime, a traditional building material, offers several natural benefits, making it a key ingredient in sustainable construction. One of its primary advantages is breathability, which allows moisture to escape from walls, preventing issues like damp and mould. Its breathability is affected by several natural processes: porosity, hygroscopicity, and capillarity. Its porous structure lets it absorb and release moisture, making lime highly breathable. This breathability enables moisture to escape from walls, reducing the risk of damp, mould, and condensation. Lime is also hygroscopic, meaning it can naturally regulate humidity by absorbing moisture from the air when levels are high and releasing it when levels drop. This property helps maintain a balanced indoor climate, preventing extreme fluctuations in humidity that can harm both buildings and occupants. Also, lime possesses capillarity, allowing it to draw moisture away from building materials through tiny capillaries. This capillary action ensures that moisture is evenly distributed and can evaporate, preventing water from accumulating and causing structural damage. Another significant benefit is its flexibility and self-healing properties. Lime can move with the natural expansion and contraction of buildings, reducing the risk of cracks. It can also repair minor cracks through self-healing, where lime reacts with carbon dioxide and moisture to heal itself. Also, lime has antibacterial and antifungal properties, helping keep buildings free from harmful microbes. Its low embodied carbon further enhances its environmental credentials, as it requires less energy to produce compared to cement and absorbs CO₂ during the curing process.

Natural benefits of cork

Thermal insulation

Cork's thermal insulation properties are derived from its unique structure comprising millions of air-filled cells. Each cubic centimetre of cork contains around 40 million cells, and around 89% of its volume is air. This natural cellular composition gives cork low thermal conductivity, making it an excellent insulator. These air pockets trap heat, preventing the transfer of warm air from the interior of a building to the cooler outside environment and vice versa. This characteristic helps to create a thermal barrier, reducing the need for artificial heating and cooling. As a result, buildings with cork insulation benefit from lower energy consumption and more stable indoor temperatures throughout the year. Furthermore, cork retains its insulating properties across various temperatures, making it ideal for use in various climates and environments. Cork insulation is often used in wall cavities, roofs, and floors to increase energy efficiency. Because it is a natural material, cork also improves the overall sustainability of buildings and reduces carbon footprints.

Sound insulation

Cork is highly effective as a sound insulator due to its natural cellular structure, which consists of millions of tiny air-filled cells. These cells help absorb sound waves, reducing noise transmission through walls, floors, or ceilings. Cork acts as a sound absorber and a vibration dampener, making it ideal for use in buildings where noise control is essential, such as apartments, offices, and recording studios. Its porous structure helps to trap and dissipate sound energy, preventing echoes and reducing reverberation in spaces. This property is especially useful for controlling impact noise, such as footsteps or furniture movement, which can easily travel through harder materials like concrete or tile. Cork's ability to reduce airborne sound (voices, music) and impact noise makes it an excellent material for acoustic insulation. In addition, cork is naturally resistant to compression, meaning it retains its shape and sound-dampening properties over time, even in high-traffic areas.

Sustainability

Cork is one of the most sustainable materials available. It is harvested from the bark of cork oak trees, which regenerate their bark after harvesting. This process can be repeated every 9-12 years without harming the tree, allowing it to live for over 200 years. Additionally, cork production is energy efficient, and the waste generated is minimal, as it is either recycled or used in other products. This makes cork both renewable and biodegradable, contributing to environmental conservation.

Moisture and rot resistance

Cork has a natural waxy substance called suberin, which makes it water-resistant. This property prevents water absorption, protecting the material from rot, mould, and mildew. As a result, cork is highly durable, even in damp conditions, and is an ideal choice for bathrooms, kitchens, or external renders where moisture exposure is high. Its resistance to decay makes it a long-lasting material with minimal maintenance.

Lightweight and flexible

Despite its low density, cork is incredibly strong and elastic. It can compress under pressure and return to its original shape without losing integrity, making it durable in high-traffic areas. This flexibility also makes cork resistant to cracking or damage when used in construction materials like flooring or render. Its lightweight nature further reduces the overall structural load when used in building projects, making installing it easier and more cost-effective.

Combining the two - lime and cork thermal render

Lime and cork thermal render is a sprayable coating mortar that combines the properties of two natural materials. The whole composition is entirely natural, with NHL 5 providing the base for the product. Recycled glass aggregates, natural granulated cork, natural pozzolans, water repellent, and other organic additives form the overall composition. The result is a sprayable or trowel-applied paste, which can be applied up to a layer of 80mm; subsequent layers can also be applied. In light of the natural breathability, the thermal performance is excellent, as lime and cork thermal render has a thermal conductivity of 0.0055 W/m2K. Applying layers thinner than 80mm, especially internally, can improve U-value significantly whilst maintaining design and functional features, such as sinks. The product is exceptionally versatile as it can be applied to many substrates, including ceramics, thermo-clay, bricks, lime mortars, and concrete blocks.