Hemp – the ecological all-rounder in construction

Attention Home Builders!

How about an indestructible, sustainable, biodegradable home that is still livable for the grandchildren?
Because whether it’s floor slabs or walls, bricks, plaster, or insulation wool, practically everything needed in construction can be made from hemp. However, while Germany, Austria, and Switzerland still have some catching up to do in the development of hemp materials for the construction industry, other European countries are already showcasing remarkable projects made from this ingenious plant material. For example, in 2005, a brewery from Southwood in the UK opted for hemp in the construction of a warehouse over 2,300 square meters in size for their beer. The walls made of blocks of hemp, lime, and cement regulate moisture and heat inside the building so optimally, thanks to their excellent insulating properties, that even in summer heat, an external air conditioning system for cooling the beer is unnecessary! Nevertheless, there are already a number of brave pioneers among us who are advocating for the raw material transition and are determined to help hemp make its overdue comeback in the construction industry. One example is the cooperative community between the Hanf-Faser Uckermarck eG and the Naturbaustoffhaus GmbH in Bösingen, Swabia, which connects Germany from north to south. There, for instance, roofs, walls, facades, and floors are insulated with hemp insulation wool, hemp stuffing, or hemp shavings, joints are sealed as always with hemp, and hemp strips are laid under floors to reduce impact noise. The hemp used is “Grown in Germany,” cultivated in fields in Uckermark, Mecklenburg-Vorpommern, processed there, and is seen by the hemp cooperative as a crucial step towards a necessary material cycle transition.

Hemp Concrete – “We should build on these stones!”

Hemp concrete (also known as “hemp lime”) has nothing to do directly with conventional concrete; it is named for its strength. It consists of the hemp shives, the woody inner part of the stems of industrial hemp plants, which are mixed with lime and water. This mixture can then be poured into walls or foundations or shaped into hemp bricks.

A strong lightweight full of apparent contradictions!

Hemp is always good for a surprise! Hemp concrete weighs only 1/6 of conventional concrete and is essentially an ecological lightweight concrete. Ingeniously, it is up to seven times stronger and three times more flexible! Wind and weather cannot harm it; instead, they make it even harder and more stable, as it literally “turns to stone.” Yet it remains flexible, meaning that when the earth moves, it does not crack like standard concrete and does not require expansion joints.

Hemp creates a cozy feel-good climate

Hemp concrete is excellent for insulation, whether in summer or winter: Cool when it’s hot and warm when it’s cool – this pleasant effect characterizes not only hemp clothing but also houses! By cooling or storing heat thanks to their thermal conductivity, the hemp walls ensure optimal temperature balance with energy savings of up to 70%!

With hemp, mold is a thing of the past!

Even in terms of moisture regulation, hemp building materials receive top marks. Because hemp walls provide a completely natural moisture exchange caused by the capillary system in the plants. Excess moisture is simply absorbed, preventing water from forming on the surface, and making mold and other pests quite unlikely. In times of severe dryness, moisture is released, naturally regulating any extremes.

Sound and fire protection included

Hemp concrete not only “absorbs” water but also noise thanks to its honeycomb structure, providing positive sound insulation values. Fire has a hard time as well, because hemp bricks are poorly flammable due to the mineral binding of the hemp shives. Should a fire occur, no toxic sulfur gases are produced, and the dangerous chimney effect, responsible for extreme heat and rapid fire spread, often does not develop at all or at least to a lesser extent.

Hemp prefers sustainability and climate neutrality – when houses grow in the field!

Industrial hemp varieties with a high fiber content are undemanding and easy to cultivate; they grow quickly and usually require no chemical treatment against pests. From a hemp field the size of one hectare, it is indeed possible to build a small single-family home! As a renewable raw material, the hemp plant binds CO2 during its growth, making a significant contribution to reducing the greenhouse effect, and hemp concrete has an advantage in terms of energy balance right from the production stage. According to the hemp concrete manufacturer Tradical, a house of average size with hemp concrete walls can save up to 50 tons of CO2 compared to conventional building materials.

And last but not least, hemp building materials can be completely recycled and are biodegradable without residues and compostable!
Not only the environment benefits, but also our health and the buildings themselves, which is why hemp should have a future in construction! With increasing demand, production costs could be lowered, and industrial hemp could become competitive as a building material alongside its many other uses. The current market leader in insulating bricks made from hemp concrete, the Belgian company IsoHemp, has recently significantly expanded its production capacity and can produce more than five million hemp concrete bricks annually in a new energy-efficient plant, which corresponds to the amount needed for approximately five houses per day.

100% natural

Hemp concrete contains no synthetic or fossil materials, and since it is naturally quite fire-resistant and pest-resistant, no additional chemical treatment is necessary, unlike synthetic insulation materials. These often contain volatile organic compounds, which are increasingly associated with the rise of asthma and severe allergic reactions.

Hemp walls “breathe”!

The exterior walls of a house are essentially its “skin” or “membrane” from a building biology perspective. Comparable to the membrane structure of the cells in our bodies, which allow molecules to pass through depending on their permeability, there is also an exchange of heat, moisture, and gases between the interior and the exterior through the walls of the house, and natural building materials such as those made from hemp can handle this complex task effortlessly! Because hemp concrete with the lime and clay plasters on its surface is breathable and permeable to water vapor. Thanks to its hygroscopic properties, it regulates air humidity, and where no moisture forms on the wall surfaces, mold spores, which can pose a significant health risk, have a hard time. With a pleasant relative humidity between 40 and 60%, the inhabitants enjoy a wonderfully healthy and cozy indoor climate that demonstrably inhibits the spread of viral and bacterial infections, allergic reactions, asthma, and other respiratory diseases. And such optimal room conditions also protect and preserve the building substance in the long term and cost-effectively.

No uninvited guests

However, where we feel comfortable, mice and other small rodents also like to find a warm place for winter or nesting! Exterior wall constructions and insulation materials should naturally prevent this, which is not so easy with persistent roommates. But hemp can do it, because hemp insulation wool is uninteresting as food and the tear-resistant hemp fibers can usually not be gnawed, making it less appealing for rodents to search for a home. And by the way – a tip from Uckermark for all gardening enthusiasts: hemp fibers are also not popular with voles. If you stuff hemp insulation wool into their holes, they will avoid the affected and neighboring tunnels because they have no chance against the strong fibers and may even get tangled in them!

Want to start small? - with a Tiny House made of hemp!

Under the motto “Small, but mine,” tiny houses are a new trend, financially easier to realize and a symbol of a simpler life with less material burden. In Swabia, there is a lot of tinkering going on, for example, with the hemp engineers in Tübingen. Together with the solidarity construction industry, they built a top-sustainable, almost CO2 neutral Tiny Hemp House in Berlin in less than three weeks. The 100% natural building materials hemp, lime, clay, and wood were carefully coordinated and combined into a functional unit, each material placed where it is best suited. The hemp was used as hemp lime with its hemp shives as insulation material and natural lime as a binder in the exterior and interior walls, ensuring perfect regulation of humidity and protecting the wooden structures inside the walls, making additional chemical treatment unnecessary. The corners of the house are rounded thanks to the materials used, as rounded corners significantly improve insulation performance because they do not create constructive thermal bridges. Additionally, air cannot flow past sharp edges and absorb moisture that can lead to mold formation, a common cause of mold growth. This is easily possible at rounded edges, keeping the walls dry. Last but not least, all those involved in the construction also emphasized the harmonious and social interaction, perhaps an aspect of sustainability that is still too little considered, which the residents of the house will surely feel!

Sources:
www.tradical.com
www.naturbaustoffhaus.de
www.hanffaser.de
www.hanfingenieur.de
www.isohemp.com
www.hanfmagazin.com

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