To expand hemp construction, combine latest materials and quick-build systems

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INTERVIEW: Steve Allin pioneered the International Hemp Building Association (IHBA), which he serves as director. An author, teacher and consultant on ecological building, Allin has been building with hemp and promoting hemp’s use in construction all over the world for more than 20 years. He is the author of “Building with Hemp” (2005, 2012) and “Hemp Buildings: 50 International Case Studies” (2021). Allin lives in Rusheens, Kenmare, County Kerry, Ireland.

HT: When we first talked way back in 2015, you said the understanding of natural materials among modern mainstream builders was low. Is the awareness of hemp growing among the broader construction industry?

Steve Allin: The awareness is beginning to expand especially where hemp materials are readily available in countries such as France, Belgium, Britain, Germany, Italy and the Netherlands. As the measurement of carbon implications of building materials and systems becomes more accurate, hemp is left standing proudly above most other competitors and its use can be more easily justified as superior.

HT: Later, in 2016 you said hemp construction could expand quickly if several large projects were to happen simultaneously; what large projects have we seen come to fruition since that time?

SA: I wouldn’t say it has happened quickly, but several large projects have been completed in the last few years. For example, there has been a succession of plans in Sweden that began with a large-scale logistics center planned around the use of hemp fiber insulation-filled panels, which seems to have led to the support for a hemp processing and insulation factory now to be built .

In Italy, the use of hempcrete for a range of structures has taken hold in certain areas, and in both Britain and France, housing projects have been built with great success.

But the media get bored quickly with stories about positive impacts even though they might offer hope for humanity. And so these haven’t been promoted as they might have been. Size matters, as has been seen recently with the 12-story hotel in Cape Town, South Africa, built using locally made hempcrete blocks.

HT: How would you describe the costs of basic hemp building materials – hurd for hempcrete and technical fibers for insulation? Has there been any progress toward parity with conventional materials?

SA: When the initial price increases of petrochemicals came after Putin’s invasion of Ukraine, there was a surge of interest in alternatives to energy-intensive expanded foam solutions for external insulation systems. This helped the awareness of hemp materials as an alternative to such toxic options for a while, but there are still massive subsidies to the fossil fuel industry that perpetuate the unfair, unrealistic price difference.

Hemp prices in Europe at least have not increased much in the last 20 years and are increasingly able to be compared to synthetic alternatives, but the speed of installation or construction is a very important part of costs.

HT: What are the most promising recent developments in the application of hempcrete? What kinds of technology are out there to speed up the process?

SA: Spray application of hempcrete is now a well-understood technology and has been recognized by many builders who need a faster manner of installation, especially for retrofit projects. Prefabricated blocks are also being used more widely as production has been increased in Belgium with IsoHemp and in Italy with Tecnocanapa Sennini, and many more in France, Italy and Portugal recently. There is also an increasing variety of internal architecture products such as acoustic wall and ceiling panels.

Another exciting product is Hempwood, which is a beautiful replacement for hardwood timber. I can see this used increasingly for both flooring and furniture as it begins to be manufactured more widely.

I think the main growth will come from combining all the innovations we have developed using hemp materials into a quickly erected modular system to be able to build quality and affordable housing. Such prefabricated modular systems provide simple off-the-shelf solutions to the whole construction process and can be specified more easily by architects or engineers overseeing any size project.

There also needs to be a wide-scale rollout of training for the many young refugees turning up on our shores, as they can’t all have a job in IT, and many will have to learn how to build the homes they will require that simply aren’t here.

HT: What else needs to happen to ensure that the hemp construction sector is ready for rapid expansion and growth?

SA: Hemp or any natural crop cannot be produced by turning on a tap. Each annual harvest will decide what is available for the market. However, at present most hemp processing facilities could theoretically triple their output as most are only working a single shift a day. With a reasonable increase in contracted planting, the agricultural sector could attempt to feed that larger supply, but the financial incentive would have to be clear for any farmers to change what they are already growing.

Ensuring that the farmers know exactly what is required from them to plant a successful crop is essential as without a good quality supply of materials from the field there will be no industry. This is where the hemp farmer relies on processors to have the harvesting machinery so that the resulting straw is of the correct quality and is gathered in the shortest time. With increased areas under hemp cultivation, there will eventually be an interest from agricultural contractors to invest and take on the role. This is the starting point of the process.

The other extremely important issue is the training of architects and engineers, who get very little information about alternative materials, especially those such as hemp. From my personal experience, the training and education of these young students is appalling. Many of the modules that are part of their degrees are years out of date and nowhere near as inclusive as they need to be to address carbon emission reductions through materials or occupancy. It seems the lecturers or heads of department are too lazy or filled with their own self-importance to bother changing things. If the professionals involved with designing our buildings don’t know about these alternatives, how are clients going to use them?

HT: National and local building regulations have been a real problem facing hempcrete construction. Are we seeing any progress there?

SA: Yes we are, even though there are obviously many projects that do get approval in every region of the world. The successes have usually been down to dogged perseverance by the client in lobbying local regulators who, if they get a chance to actually see and understand hempcrete, give approval readily.

In the USA the system for material approval is different than in the EU or most member countries. In the States, how a material is used is more important than exactly how it performs. This has made it easier for the U.S. Hemp Building Association to gather the funds to enable them to insert hemp materials into the ASTM Standards. In Europe, we are up against a set of parameters set by the synthetic materials industry, which relies on laboratory performance with a test environment unlikely to be found in reality, with the focus on Lambda values especially. This, of course, has big impacts on how buildings are designed, built or retrofitted to realistically address climate change and energy use.

To address this situation in Europe, the IHBA is working with the European Industrial Hemp Association in a working group to set the parameters to present to European regulatory bodies, which will make it far easier for them to be detailed in building plans.

HT: How can hemp growers, building suppliers and builders benefit from governments’ growing emphasis on CO2 removal? Are there financial incentives being developed?

SA: This is an area getting much attention at the moment, but I am not sure we have totally accurate methods of measuring carbon sequestration, especially in the soil. I am also very skeptical of any carbon credits that are produced only as a way for big, polluting corporations to pretend they are mitigating their own emissions. Carbon credits are being invented based on several different methods of accounting for carbon storage or removal, but these will need to be part of a thorough, transparent evaluation of how the crops are grown, harvested, processed and then used, to be able to determine how stable the carbon actually is.

Far more important is measuring all the savings being made by not having ill health from our built environments, from helping agriculture to be less toxic and damaging, and saving massive amounts of energy and money by insulating our existing buildings. This can be seen by the three largest such buildings in the last 15 years: The Adnams Brewery distribution Centre and the Wine Society warehouse both in the UK and the replacement hempcrete facade of the Voorst region Town Hall in the Netherlands have each shown that with hempcrete envelopes, heating and cooling bills of €40,000 – €50,000 have been reduced to zero. We can only imagine how many emissions we could remove by doing this.

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