“Ten years from the construction of the first Hemp house, its use in construction is now widely known throughout the entire national territory, and not only for “green building”.

We could state that you were among the first to use Hemp in the field of what is called “green building”, how did you start and what progress has been made in the sector to present date?

My personal experience with the use of Hemp started in the Nineties when I introduced, in the projects, the use of Hemp fibre mats (created with the fibrous part of the plant) for the insulation of the buildings; even though at that time the material was hard to find in Italy and was produced abroad (France and Germany).

Regarding the use of “Hemp shives” (fragments of the “woody” parts of the Hemp stalk) the interest came up in the early 2000s, due to the encounter with Bretoni who had utilised this material for a long time already.

In the years following, during various study trips in Brittany, where the use of Hemp in construction practically had recommenced, I visited various building sites, buildings newly made or renovated with Hemp, as well as manufacturing companies, well-known operators in the sector and researchers. I learned various building techniques, the ways of laying it and I gained a deeper knowledge regarding the suitability of the materials according to their uses. In that period I had the occasion of presenting the building sites and the creations in Hemp I had visited abroad during Conferences on green building to which I was invited. In 2008 I designed the first house in Hemp ever made in Italy, constructed between 2009 and 2010 with materials and labourers from Brittany, because, in that period in our Country, besides the lack of knowledge on the building techniques, the materials weren’t available either.   

Since then, due to the extraordinary performance of the material, I continued to study and acquire deeper knowledge of the different uses, by participating in the EU Project “INATER’: Isolanti Naturali e Terra cruda” (“Natural Insulation and raw earth”) (2009-2012), which involved, besides Italy, French, Belgian, Portuguese and Swiss partners. 

One of the objectives of the Project ‘INATER’ was the professional training and the divulgation of Hemp in construction, and hence a series of initiatives of educational and informative nature were created in collaboration with ANAB (National Association of Bio-ecological Architecture), AssoCanapa (National Coordination Body for Hemp Cultivation), Local Authorities and Companies. Meanwhile a new and more general interest in Hemp was growing in Italy, from an agronomic point of view as well as with regard to its possible uses; some Universities commenced research activities on the topic, there were encounters between Members of the Parliament and the Commissions, in preparation of law n. 242/2016 and subsequent decrees. All this has made it possible to raise awareness on the potentiality of the use of this material in construction as well, and to create manufacturing and/or importing companies for the construction with Hemp.

I feel that, today, 10 years from the construction of the first Hemp house, its use in construction is now widely known throughout the entire national territory, and not only for “green building”. This seems to be an excellent result to me, even though there is still much work to be done !!!

Which are the main benefits that can be obtained from the construction of houses, in which hemp and lime are used? In this regard, correct me if I’m wrong, you designed a house in San Giovanni in Persiceto (Bologna), entirely made out of Hemp.

The extraordinary qualities of Hemp, if used correctly with other suitable materials, are numerous, both from the point of view of the high degree of comfort for those living in the buildings and with regard to the low energy consumption needed for air-conditioning, as well as for the extremely low environmental impact for  production-utilisation-disposal. It is known that the building industry is among the most impacting on the environment and as a consequence is affecting the current climate changes considerably, while the cycle of the materials (LCA) in Hemp generally has positive results, since:

  • CO2 emissions are drastically reduced during their production, rather, research studies carried out by various Universities and Research Bodies (both foreign and Italian) demonstrate that a material (wall, blocks, screeds, plaster etc.) in Hemp and lime retained stored inside itself a higher quantity of CO2 than the quantity emitted during its entire life-cycle, hence buildings constructed (or even better, renovated-re-qualified-restored) with Hemp materials can become true “CO2 storage tanks”.
  • the demolition-disposal of Hemp and lime material can be of extremely low environmental impact, it can even be done directly by crushing it and scattering it in the field, as an agricultural soil improver, and not in expensive and unmanageable landfills for “special” and/or “toxic-hazardous” waste.
  • the thermalacoustic insulation is high, and, together with the natural properties of thermohygrometric regulation of the spaces and thermal conductivity, guarantees an excellent living comfort.  
  • it is possible to use just one material (Hemp and lime) to create the entire casing of the building, simplifying the manufacturing processes, reducing the costs, avoiding the onset of issues connected to unhealthy moulds and condensation, which unfortunately are present in many, also recent, buildings.
  • the energy consumption for air conditioning of the buildings is very low, general air-conditioning and forced aeration aren’t necessary in the summer period, while the air-conditioning in the winter period is very limited, hence reducing, besides the management costs of the  building, also the construction costs and the costs of installations and disposal.

The first building (a semi-detached house) made of Hemp in Italy (winner of the “Green Economy 2010” Award) constructed in San Giovanni in Persiceto, is not connected to the gas network,  is equipped with photovoltaic and solar thermal energy systems, which abundantly cover the requirements of heat and power inside the building, which gives substantial benefits in managing the house also from an economic point of view.

In seismic hazard territories, Italy is a Country with various seismic hazard zone, could Hemp be an additional ally?  

I used Hemp mixed with lime to reconstruct some buildings destroyed by the seisms of 2012 in Emilia, approved projects entitled to Community support for their reconstruction, earthquake-proof buildings, completed and tested, in which the families returned and in which they have lived for quite some time now. In order to establish the dosages and mixtures of Hemp and lime to be used in restorations, I asked the University of Modena-Reggio Emilia to carry out tests on different samples we had prepared, to determine the most suitable and performing ones. All the bearing structures were created in wood (another material I have always used in my projects) using a “frame” system, the way buildings have been constructed since the Middle Ages, while the  infill walls, the insulation screeds, the plasters, etc. were made with a mixture of Hemp and lime, directly with the French “banché” method; a building system I consider the most adequate and from which the bests performance is obtained, while easy to carry out directly at the building site.

The frame structure in wood (beams and pillars) has been completely embedded in a Hemp and lime cast and in the event of an earthquake the two materials, both extremely elastic, tend to “move in synchrony”.

This will prevent any possible“overturning” of façades and/or major damage to the structures; as demonstrated the “first house in Hemp” which, although it was situated in the “crater” of the seism, was not damaged by that tragic event; of course, it’s all proportional to the magnitude of the earthquake.

Furthermore, the lime that was used will preserve overtime both the wood and the hemp shives from possible attacks of parasites while “thermal bridges ”will be avoided as well.  

You are the project leader in Italy of the project ‘UE Canapalea’, what is it?

My research activities have continued through the participation in a second Project of the European Union, called “CANAPALEA” (Latin for hemp straw), which was developed in collaboration with French, Spanish, Belgian partners and the representative for Italy was ANAB, with the aim to obtain deeper knowledge about the topic and about the evolution of the different building techniques and materials made with Hemp in the various  participating countries; sharing the training modalities for those who intend to utilise Hemp in constructions: Technicians, Producers, Enterprises, Craftsmen, Self-builders, etc.; make known and popularise Hemp and its uses in construction in the various partner countries through Conferences,  Seminars and Workshops. The results were beyond expectation and many stakeholders participated, for example, in the International Convention “ Hemp and its Ligands” we organised in Rome at the University “Roma 3” over 250 technicians and operators participated; also in the events organised by the other Countries there was a large participation.

This project was then ‘transformed’ in an editorial project, how much interest did the public opinion and insiders show on the topic of green building?

With the objective to divulge and, even more, to inform about the qualities and potentialities of this material, it was decided to create a publication: “Constructing with Hemp, Building sites, techniques and production chains in Europe“. The volume is the result of the work done by a team of experts coming from the various European partner countries of the EU Project “CANAPALEA”, and had the intention to review the state of the art of constructions in Hemp throughout Europe; it was published in original language in France, Italy, Spain and Belgium. It covers over 300 pages in colour and analyses the various aspects of constructing with Hemp, it illustrates and records the creation or restoration with Hemp of 25 buildings in the different countries: public and private buildings, new single houses or reconstructions, structures for tourists, the tertiary sector and production plants; it contains in-depth studies on natural materials, in particular on Hemp, and treats the various construction techniques and the production chains of Hemp in the different countries. 

From your point of view, how do you imagine the future of Hemp in Italy?

An important clarification must be made, Hemp is a plant with specific characteristics depending on the variety, the location and the cultivation methods, the impact of seasonal factors, etc. but its products (fibre and shive which can be used in constructing) are not very different from one another and they have very similar characteristics, at least in Italy. The difference is made by the other compounds with which the Hemp products are mixed-assembled. For example, the performance of Hemp can change significantly according to which ligand it is mixed with (hydrated lime, hydraulic lime, cement, plaster, clay, etc. etc.), according to the dosages of the various compounds, the laying methods (cast in-situ, sprayed, in blocks, etc.) and the possible combination with other materials. 

The  “Hemp production chains” in development in our country should consider the entire pathway and not just the parts which are considered most interesting (for example the flower-tops, the seeds, THC, CBD, etc.) while ignoring the rest (stalk: fibre and shive) or even thinking of burning it. It is in fact necessary to develop production chains that use this part of the plant as well, which is sometimes erroneously considered “waste product”. Construction is one of the fields in which it can be widely and virtuously used, a small example of circular economy.

Lastly, it is important to use Italian Hemp, cultivated and processed in our country and not just do a mere commercial job of importation, the high environmental costs of transport would “devalue” those products.

Hemp and its derivatives produced in Italy have nothing to fear from hemp from other Countries, on the contrary, for centuries we have been among the main producers when it comes to both to quantity and quality and we could, without any doubt, return to that level if solid and complete “chains” are developed, based on research, regulations, formation and shared information.

Hemp could have a comeback and become the “queen of our lands” again, as it has been for centuries and from which humans benefited and can benefit in many ways, in many sectors.