Focus on hemp in construction. The use of the Canapulus
One of the main protagonists in the new Green New Deal is certainly the Hemp. The properties of this plant are multiple, known for millennia, the first evidence of its use can be found around 10,000 years ago, in Central Asia. Already in 2737 BC in a treatise on Chinese medicine, hemp was referred to as a medicinal plant. Not only the recreational and medicinal properties have been known for millennia, butalso the property of its fiber has been exploited for centuries: the sailings of the Caravels of Christopher Columbus were made of hemp fibers for better resistance, as well as the Navy ships English Military. Hemp was also sued for printing ancient books with which sacred texts and manuscripts of various types. In short, hemp has always been used in many applications and today also in construction. As we have repeatedly stated, climate change is revolutionizing the habits and lifestyles of the human being, forcing us all to choose solutions that are as little impacting as possible on the environment and its eco-sustainability. Let’s look at some features.
One of the properties of Hemp is bioremediation, the ability to absorb heavy metals in the soil, which in many areas of Italy is very important: in fact, some experiments have been started in the area of the Ilva industry (Taranto). Obviously the investment can be interesting if the use of the biomass is destined to the industrial market as the production of bio-building material in hemp. In this case it would be economically viable. The use of hemp shwos advantages in comparison to wood, ashemp materialregenerates in a year, the plant has rapid life cycle, does not require particular quantities of water and herbicides or pesticides : it certainly appears to be an interesting raw material. In addition, the characteristic that distinguishes hemp wood from other woods found in nature is its particular conformation: hemp is made up of a series of cavities which, during life, allow the passage of nourishment, once dried, the stem in addition to being extremely lightweight, it is also highly breathable. Construction materials that can be made using hemp are many: hemp blocks, plasters, stuccoes, screeds, mortars, paints, insulating panels and the various derivative products. However, the absolutely most important aspect, in the circular economy, is that hemp building materials are totally recyclable and biodegradable at the end of their life cycle. In fact, in the case of demolition of the building,hemp bricks can be calcined in a furnace, obtaining new lime, or mixed with new lime or mortar with the same ingredients to obtain new materials, or used as a soil improver in acid soils or in arid-saline soils.
The hemp brick or hemp block is composed of the Canapulus, the crushed stem of the plant agglomerated with dolomitic lime or NHL 5 hydraulic lime, various additives and water.
The properties of this building material are different:
- it is able to effectively isolate the internal environment from the external environment thanks to its large coefficient of thermal conductivity. Hemp bricks are also able to maintain constant humidity levels in indoor environments, avoiding condensation in thermal bridges and therefore residual moisture or mold on the walls. The hemp house, or rather with hemp brick walls, increases the living comfort and improves the healthiness of the rooms. A very important factor given the large number of hours that each of us spends in at home.
- From the environmental point of view, another very important characteristic of hemp bricks is the fact that the use of the hemp plant removes CO2 from the atmosphere, thanks to the ability to absorb important quantities of COS in the growth phase of the plant.
- The blocks in canapulus and lime are also fireproof and have a ductile behavior with respect to the movements of the supporting structure in the event of an earthquake;
- It is a material with high thermal inertia; with a thickness of 40 cm, it can reach a thermic difference of more than 24 h
- Their handling is easy since their density varies from 300 to 425 kg / m3;
The negative aspects are linked to the shape of the bricks that, as can be seen in the photo above, are rather bulky and are not handy. Furthermore, canapulus is not always readily available, in Italy, in fact itis often imported from France (therefore, with environmental and economic costs linked to transport, higher or equal compared to other construction products).
Lime and hemp
As an alternative to using in blocks, lime and hemp can be mixed directly on site and used as a plaster for both interior and exterior use. If applied in the attics or in thermal screed, it becomes optimal for the insulation and thanks to the transpiring and anti-humidity properties it maintains an excellent salubrity of the air, in increasinglyclosed domestic environments, in order not to waste energy considering the legal obligations on energy efficiency.
Sound absorbing hemp panels
There are also fiber insulating panels (consisting of the part that covers the stem), excellent for use in prefabrication in wood, to isolate the inside of the walls or to insulate attics.
Plaster in lime and hemp
It is a natural pre-mixed plaster, with excellent coverage and filling, suitable for internal and external glazing. It is a high-quality ecological product, because it is created from raw materials of natural origin: hemp powder, NHL5 natural hydraulic lime and with specific additives that, appropriately dosed and mixed with clean water, give rise to an easy-to-apply finishing mortar. It has a medium-fine grain size, thermal insulation properties, low incorporated energy and the ability to absorb CO₂ from the atmosphere during its production process, respecting the principles of environmental sustainability. CANAPASTUCK has all the qualities required of a building material in line with sustainable development.
- reduces mold and condensation thanks to high breathability
- also ideal for the restoration of historic buildings
- absorbs and releases moisture
- improves acoustic comfort thanks to its sound-absorbing power
- eco-friendly low energy incorporated
- applicable on old plasters
- fire resistant
- unassailable by insects, rodents, parasites
- at the end of the life cycle: renewable, recyclable, reusable
Self-supporting hemp wood panel
Self-supporting and rigid thermal and acoustic insulation sheet. Ideal for the construction of walls with cavities, counter-walls, reconstruction of walls with insulating cavities, usable as insulation in frameworks, for ceilings and floors, or as an alternative to all applications where plasterboard is envisaged. It offers many advantages compared to traditional solutions, thus allowing to achieve high technical performances with reduced thicknesses and weights.
- Insulates from cold and heat (excellent thermal offset values)
- It improves acoustic comfort thanks to its sound-absorbing power
- Easy to apply, even for dry construction
- Ideal in combination with lime and hemp products
Hemp green building: prices
The costs of green building in hemp are higher than in classical building, due to the factors we indicated before: poor distribution of the supply chain in Italy and limited presence in the territory of supplier companies. The hemp and green building market, however, seems to be expanding and with the spread of its use prices may fall in the future. Some regions provide incentives and tax deductions for the use of bio-derived or recycled materials (in the Piedmont Region, these incentives where introduced by the Regional Law of 4 October 2018, n. 16).