Hempcrete is used as a highly insulative wall material. It is a carbon-negative, natural, and lightweight construction material that provides highly efficient temperature and moisture control. It is also formable, dynamic, one-seventh the weight of concrete, and cures within hours.
What Are the Benefits of Hempcrete?
好处是多方面的。它具有高度的绝缘性,调节湿度,防止哮喘,防火,防白蚁,防鼠,防止霉菌和上升潮湿。它永远不会腐烂。它保留了木结构的房屋框架,零垃圾填埋,封存碳,并且无毒。
Related Post:Earth Sheltered Home: An Eco-Friendly, Passive Housing Alternative
What Is Hempcrete Made From?
Hempcrete is made by mixing the inner woody core of the stalk known as the hurd with a natural, lime-based binder, and water.
To separate the hemp fiber from the woody core, the plant stalk is left to rot (a process called retting) for 4 to 6 weeks. Microbes break down the pectin in the stalk to facilitate separation. After retting, stalks are dried and then passed through toothed rollers which crush and break the woody core into smaller pieces.
Hemp hurd is simply a byproduct of hemp fiber production. What was found (by the French) is that hemp hurd could be used as an aggregate for construction, and its addition dramatically improved — in several capacities which this article will endeavor to cover — the performance of the structure.
它来自何时何地?
If you’ve ever had the pleasure of traveling to France, you might have seen the many old, oak-frame colombage buildings. Between the oak, mixtures of lime, straw, rubble, sand, and clay are stuffed. No matter how hard you search online, you won’t find the name of the genius who swapped out straw for hemp hurd. But since then — at some point in the 1980s — the idea spread across France, into the UK, and all through Europe. Today, there are thousands of hemp houses on every continent.
大麻混凝土比混凝土好吗?
Hempcrete may be one of the most Googled phrases in the industry. Perhaps it was a mistake to fix “-crete” on the end of the word, because, even though it does roll off the tongue, hempcrete is very different from concrete.
混凝土是一种用于创建地基和承重结构的材料。它很重,摸起来很冷,而且没有绝缘的特性。
Hempcrete, on the other hand, is super light. In fact, it is one-eighth the weight of concrete. It is non-load-bearing and best described as a masonry infill material with a porous, airy, fibrous composition. It is currently in the spotlight for several reasons: It’s a high-performance insulator, able to regulate the moisture content of the house (providing a sense of comfort and relief from allergies), and so eminently carbon-negative it can mitigate the carbon footprint of the entire house building process. For those who want to delve deeper into the building science behind the performance of hempcrete, I’ve written more extensivelyhere.
大麻酱里有什么?我能自己找到吗?
Hempcrete has three constituent parts: hemp, lime, and water.
Hemp, and Where to Source It
在澳大利亚,大麻刀才刚刚开始种植并推向市场。(A couple of notable enterprises being Hemp Homes Australia andX-Hempin Tasmania where 80% of the hemp in Australia is currently farmed).
In Europe, a large industry is established and growing, with processing facilities in France, Holland, and Germany. The last house I built — working in Scotland — was made with Lithuanian hemp.
Over in the US, hemp production has exploded since the Agriculture Improvement Act or Farm Bill of 2018, finally allowing hemp cultivation after many, many years.
The Binder
As you might assume, the binder is what binds the hemp shiv into a solid mass. The binder consists of either hydrated lime or natural hydraulic lime. Hydrated lime (or air lime) has no impurities and is made by kiln-firing limestone. The firing process removes the carbon molecules from the limestone and converts it into a dry powder. When you want to use lime as a binder or mortar, you introduce carbon dioxide again, essentially converting the lime back into limestone as it absorbs surrounding CO2. This is what’s known as the carbon cycle.
The other lime, hydraulic lime, is also kiln-fired using the same process. The difference being hydraulic lime has added or existing impurities known as pozzolans.
Why Add Impurities and Why Give Them Such an Exotic Name?
添加白火山灰会使石灰凝结成一种化学物质,在二氧化碳和水的存在下,石灰又会变成石灰石。这一套更快更强。固化也可以发生在大麻混凝土墙的更深处,在那里空气或熟石灰可能没有足够的二氧化碳来在方便的时间框架内固化。和名字吗?2500年前,罗马人在那不勒斯附近的波佐利(Pozzuoli)开采波佐兰,在维苏威火山(Vesuvius)的注视下。
One tremendously interesting fact is that hemp hurd has a high silica content. And silica just so happens to also be a pozzolan. So the actual hemp itself serves not only as an insulative aggregate, but to increase the strength and set speed of the lime.
与现代硅酸盐水泥相比,使用天然石灰砂浆有许多好处。你只需要看看罗马圆形大剧场或万神殿,就能看到活页夹的好处,它更灵活,更透气。这是自然建造者对他们的方法如此热情和直言不讳的众多原因之一。它们通常是工业化前的,非常可靠,碳足迹很小,而且它们建造的建筑寿命更长。2022世界杯四强亚盘赔率
Lime is very common across the globe. Depending on your country, you may only be able to source either hydrated or hydraulic in their natural forms. But you can always add a pozzolan if needed.
Understanding lime is beyond the scope of this introduction as the chemistry and interactions between hemp and lime are complex (and tremendously interesting). Various lime choices exist and are on a sliding scale of sustainability and utility. Amusingly, lime is a contentious subject in the natural building community. Have a read herehttp://www.stastier.co.uk/nhl/topics/mineralogy.htm
大麻房子是如何建造的?
大麻房屋通常使用标准的木棒框架,你可以在新建或翻新中看到。棒状框架充当承重者和骨架,由大麻混凝土包裹或包裹。在英国,螺柱被称为6 × 2或约150mm × 45mm。在澳大利亚,标准90mm x 45mm螺柱被使用,实际上工作有利于一个大麻混凝土建造。This works because as hempcrete surrounds the frame, you want as much meat or expanse of hempcrete on each side of the stud — the wall mass to the inside of the wall and the wall mass to the outside — with the stud being in the center.
In other words, the more mass of hempcrete you have that is unbroken by timber stud work, the stronger the hempcrete, which is why you want the stud frame in the dead center of the wall detail. You generally want more than 80mm of hempcrete on either side of the stud frame which is easy to achieve as most hempcrete wall thicknesses are called out between 250mm to 400mm.
Formwork or Shuttered Hempcrete
The most common method of construction is to create formwork or shuttering and to pour the wet hempcrete mixture into the form from buckets. It has the lowest barrier of entry in terms of skill, and often homeworkers and the community can jump in and ferry buckets under the guidance of a skilled hempcrete contractor. The formwork itself doesn’t have to be super strong as it isn’t a liquid in its workable form. Hemp as a material has quite a lot of friction, so as it is poured into the forms it does not suffer droop. In fact, once poured, the outside edge of the wall is tamped to create more compression and solidity. The tamper job is a premium, sought after, and satisfying role on the hempcrete worksite.
Spraying Hempcrete
Here you can see the hempcrete sprayer in action.
This process is essentially run by two pumps: A conventional concrete pump for the lime, and a specialized, hemp dry pump (premixed hempcrete still hasn’t been successfully run through a single line as so much friction is encountered). The two are shot separately through the lance and converge on the wall with the lime binder battering and coating the hemp upon impact. This method is great for creating curves and infilling hard to hand-place spots, such as where the wall meets the ceiling or spots you might have missed during hand placing. Toward the end of this video, you can see how a horizontal batten is attached with the leading edge being the reference point for the finish line of the hempcrete. From this batten, a straight edge is hung, allowing the wall to be flattened, and shaving off high spots on the fly.
Hempcrete Blocks
Many companies are racing to bring hempcrete blocks, bricks, and panels to market. Some see it as a kind of holy grail of mass-produced, industrialized, and affordable hemp housing. Bricks can be freighted to the site and laid by masons with a lime-based mortar. This method is still in its infancy and great attention must be taken to detailing because bricks cannot shroud the frame as spray-applied or formed hempcrete. With air gaps around the timber frame, the opportunity for cold bridging can occur, causing loss to the insulative abilities of the wall.
Which Method Would Work Best for Me?
Some prefer the sharp lines and modern look of hand-placed shuttered walls. Others prefer the rounded and blended look of sprayed hempcrete. There is a fair amount of crossover I would say, and you can achieve modern and classic styles employing either of these methods. In terms of efficiency and quality, some say spraying is quicker. Others say spraying is too messy because you have about 15% that doesn’t make it onto the wall. Still, others say hand-placing can be limited. Both methods have their pros and cons, and the jury is out as to which will eventually come out on the top as the future industry standard.
When you add up all the benefits of hempcrete: health and respiratory, environmental, energy savings, safeguarding against rodents, rot, molt, and termites; and the actual comfort factor of a finished hempcrete house, you find it hard to argue against the fact you’ll be seeing a whole lot more of hempcrete in the future.
威尔·布莱恩(Will Brain)是澳大利亚墨尔本的一名大麻贩子。You can find more of his writings and documentation of his work as a contractor atwww.brainbuilt.com.au
Monty Chong-Waldensays
Thanks for the article Will.
A few notes:
Name of original chaux et chanvre genius = Charles Rassetti
Another term for hempcrete = hemp-lime
It “never rots” if it doesn’t stay permanently wet and is allowed to dry out
The recarbonation of lime is called the lime cycle
Another method for building walls other than slip-forming and spraying is factory panel and infill, which won’t have air gaps in it – seehttp://www.calmura.ca
Definitely looking forward to many more hemp-lime, or monolithic biocomposite buildings in the future!!
Dave Crabillsays
Great article, thanks!