Traditional Crops insulating Traditional Buildings Today
Once commonplace, industrial hemp is a traditional crop making a comeback in UK farm rotations and is perfect for insulating traditional buildings.
Grade II listed Long Furlong House, Highgrove Estate, owned by the Duchy of Cornwall. The original part of the house is late 17th Century with later extensions. Industrial hemp insulation was specified and used in the recent renovation to insulate roof areas, primarily in the bat loft. Photo credit: Duchy of Cornwall.
Historic buildings are a testament to our architectural heritage, showcasing intricate designs, unique materials, and complex structures, and they present a unique challenge when it comes to energy efficiency and insulation. The preservation of their historic character must be balanced with the need for modern comfort and sustainability.
One element of our farming heritage lends itself perfectly to this task but has not been as well preserved. Cast yourself back to the 1500’s, and you find a time where every farmer in the land was mandated by the Crown to grow industrial hemp - a fast-growing crop, useful for its tough fibres and woody core know as ‘shiv’ or ‘herd’. A traditional crop grown from Scotland to East Anglia, Wales and the West Country, it was stigmatised from the 1920s, and the skills for farming and working with its components almost lost. However, after a 100 year ‘oil age’ blip, following other countries around the work industrial hemp is now making a comeback in the UK for agriculture, construction and more.
Members of the Listed Property Owners Club can access the full article and more in Listed Heritage Magazine (Dec 2024). We explore how industrial hemp and natural fibre insulations can be used to insulate walls, floors, partitions, and roofs effectively in historic buildings, enhancing their thermal performance while maintaining their historic integrity.
IndiNature's industrial hemp insulation in the Loft at Long Furlong House, Highgrove Estate. Photo credit: Duchy of Cornwall
Scottish Borders, 2024 industrial hemp trials reviving this traditional crop in the region. Photo credit: IndiNature / UpHere Media
Industrial hemp has an incredible range of benefits, improving soil health for future crops and supporting biodiversity gain, while also providing durable, breathable fibres and shiv to make breathable natural fibre insulation, hempcrete blocks, plaster and other products in the era of mitigating and adapting to climate change, and is well-suited for use in historic buildings:
· Breathability: Perhaps most importantly, natural fibres are highly vapour breathable, allowing moisture to pass through the material without causing damage to the building fabric. This breathability is essential for maintaining the health of historic structures, preventing moisture buildup and reducing the risk of dampness and decay.
· Thermal Performance: Natural fibre insulations have a high heat capacity, meaning they can store and release heat more effectively than conventional insulations. This helps regulate indoor temperatures, keeping buildings warm in winter and cool in summer.
· Acoustic Performance: The dense fibres of natural insulations are excellent at absorbing sound, reducing noise transmission between rooms and from external sources. This is particularly beneficial in urban environments where external noise can be a significant concern.
· Sustainability: Natural fibre insulations are made from renewable resources and are biodegradable. Hemp, in particular, is a carbon-capturing material, meaning it absorbs more CO2 from the atmosphere during its growth than is emitted during its production and installation. Industrial hemp, absorbs 8-20 tonnes CO2 per hectare from the atmosphere as it grows from May to August, converting it into carbon and storing it within their fibres. When used as an insulation material, this biogenic carbon remains locked away for the life of the building, making hemp insulation a carbon-storing material.
· Durability: A resilient and long-lasting fibre, historically grown for its strength and durability for ropes and rigging in the Navy, industrial hemp insulation can withstand the test of time, providing effective insulation for decades without significant degradation.
· Thermal Mass: Hemp insulation also has the right amount of specific heat capacity, not too much like masonry and not too little like conventional insulations. This means it can store a modest amount of heat during the day and release it back into the building at night, preventing high peaks and low troughs of temperature and creating a more even and comfortable indoor climate with less energy required to heat or cool buildings.
· Easy Installation & Removal: Hemp insulation is flexible and can be easily fitted between joists, rafters, and partition walls, minimizing gaps and reducing the risk of thermal bridging. It is also compatible with a wide range of structures, with flexibility for those with uneven surfaces common in historic buildings. For listed buildings, crucially, it is also easy to remove, if necessary, does not alter the structure of the building, and can be re-processed at the end of life.
· Biodiversity and soil health: before it reaches buildings, hemp has already had a great impact in the fields, supporting improved soil health in farm rotations with deep roots breaking up the soil, and with few inputs required and no pesticides it helps local biodiversity too.
IndiTherm fitting in an a historic building loft. Photo: IndiNature
From January 2024 in the UK, IndiNature manufacturers the first locally grown, made and British Board of Agrément certified industrial hemp insulations, with IndiTherm followed by IndiBreathe Flex now available. Yorkshire’s finest industrial hemp is manufactured into insulation the Scottish Borders. From 2025 UK farms can also more easily re-integrate industrial hemp into their rotation with specific legislation recognising its myriad benefits for textiles and construction, and difference from its more potent cousins. With more farmers now exploring re-farming the crop, alongside sheepswool, woodfibre and other natural fibres it is a versatile and sustainable option for insulating historic buildings.
Insulating historic buildings with natural fibre insulations, particularly industrial hemp, offers a sustainable and effective solution for improving the thermal performance of these structures. By choosing natural fibre insulation, property owners and managers can preserve the historic character of their buildings, improve energy efficiency, and contribute to a more sustainable future.