Hemp straw chopped and cleaned for hemp plaster - coarse

Hemp Straw for lime plaster | Lincolnshire Lime

A vast range of sustainable building products are currently being made from all parts of the hemp plant for use in restoration and new build projects. Hemp construction uses renewable crop-based materials which absorb carbon dioxide (CO2) as they grow, providing an opportunity to capture and store CO2 in the fabric of buildings. Hemp fibre is made into 'user-friendly' recyclable loft insulation which does not contain harmful ingredients and compressed hemp shiv is used to make a fibre board but by far the most exciting development is Hempcrete, a material that can be used for construction.

The wood like core of a hemp plant with a lime binder to make a biocomposite, called Hemp-crete, that can be cast or sprayed into the walls of newly built houses. Hempcrete is a non-structural wall infill to be used in conjunction with timber frame structures. Hempcrete walls provide all the insulation the building needs. Floor and roof insulation can also be achieved with the hemp lime biocomposite.

Hempcrete provides carbon neutral, low energy, highly insulated structures and can be suitable for both new build or refurbishment.

Hempcrete is also an excellent choice for renovating old buildings with insufficient insulation where a layer of Hempcrete can be applied to the interior of the building providing some insulation and eliminating drafts.

The process of turning hemp into houses is not complicated. Hempcrete is hemp shiv combined with natural lime and water. This creates a mix which is then poured into removable wooden shuttering and lightly tamped down to produce a 450mm wall cast around a timber frame which provides structural stability.

Hempcrete buildings have many good properties some are listed below:

Low embodied energy - low energy used in production HemShiv for Hempcrete.

High embodied carbon - Large amounts of carbon locked up in Hempcrete buildings.

Very good thermal insulation properties

Good noise insulation properties

Breathes, helps to prevent condensation

Non-flammable and Self draining

Resistant to rodents, insects, fungi and bacteria

Flexible and crack resistant

Visually attractive - any shape can be constructed with Hempcrete.

Light weight

Improves with age

Recyclable

Sustainable - Hemp is grown every year

HOW IS IT BETTER FOR THE ENVIRONMENT?

Hemp construction uses renewable crop based materials which have absorbed carbon dioxide (CO2), providing an opportunity to capture and store CO2 in the fabric of buildings. It is claimed that hemp and lime can lock up approximately 110 kg of CO2 per m3 of wall.

BREATHABILITY

Hemp lime composite materials also absorb moisture vapour and allow it to pass through the fabric of the building; This effect is known as 'breathing walls'. Structures built from non-breathable materials can trap moisture, which is likely to cause mould growth, particularly if there is insufficient ventilation and high levels of condensation. Breathability also helps to protect the fabric of the building, particularly against decay in the timbers.
Hemp and lime masonry construction is unique because it provides a method of building which is structurally sound, can provide thermal and acoustic insulation, thermal mass and storage but can also be used as the external skin of a building. It is simple to construct, using just one method to meet many very different requirements for walls, floors and roofs.