Construction


Tradical Hemcrete, a combination of hemp chips and lime-based binder, is the wall material of choice for a group of builders and designers in North Carolina

Devember 7, 2009 – Fabrics and rugs made with industrial hemp are often cited as acceptably green alternatives to floor coverings made from petrochemicals, or to woolen rugs treated heavily with insecticide. But hemp also has found its way into another domestic application.

And it is not the first alternative use that may come to mind.

Nauhaus Institute, a North Carolina-based coalition of designers, engineers, builders, developers, and others devoted to green construction, has been working with hemp as a wall-construction material. Called Tradical Hemcrete, the material is essentially a lime-based binder and industrial hemp chips (derived from the woody, pretty much unsmokable core of the hemp plant) that, when mixed with water, can be sprayed over a substrate on an exterior wall or poured into forms around timber or stick framing to create a thermally resistant but “breathable” barrier.

A wall-material bakeoff
As noted in a recent story in Asheville, North Carolina’s Citizen-Times, Nauhaus (pronounced “now house”) has two homes under construction that will feature Hemcrete walls. Nauhaus says on its website that, overall, hemp met sustainability, performance, cost, and aesthetic criteria better than competing materials.

“On the natural building side, we feel that earthen mixes don’t have adequate thermal performance in our climate while the vulnerability of straw bales to water damage concerns us,” the group’s partners say on the Nauhaus site. “On the high-performance commercial side, we are skeptical of the long-term durability of SIPS walls and feel that double-stick frame systems are too complex and prone to air infiltration weaknesses. These and other problems seem to be solved by what to us is a new material: Tradical Hemcrete.”

Hemcrete also is billed as insect- and fire-resistant. One issue the group couldn’t get around, however, is that, while industrial hemp products can be imported into the U.S., it is illegal to grow hemp here. Tradical Hemcrete is made in the U.K. by a division of Belgian firm Lhoist Group, a specialist in calcined-limestone products, and is distributed in the U.S. by Hemp Technologies, of Asheville.

A green quandary: shipping from the U.K.
The Citizen-Times story points out that shipping costs make Hemcrete considerably more expensive — the approximately 1,900 sq. ft. of Hemcrete required for one of the Nauhaus projects, with 3,100 sq. ft. of interior space and 12-inch-thick exterior walls, costs about $56,250. But Hemcrete walls also require less lumber, which reduces framing costs 30% to 40%, Greg Flavall, a co-founder of Hemp Technologies, told the paper. Another advantage to Hemcrete, says Nauhaus partner Chris Cashman, is that it serves as “your Sheetrock, insulation and Tyvek all rolled into one.”

Building-performance costs in both Nauhaus projects will be significantly lower than conventionally constructed homes of comparable size, although the smaller of the two structures, a 1,450-sq.-ft. four-bedroom that will serve as a Nauhaus prototype and test house, will have 16-inch-thick walls and solar panels on the roof to bring energy usage to net zero.

Not surprisingly, Nauhaus partners advocate legalizing industrial-hemp growing in the U.S. “Our feeling is, what a great crop this would be for North Carolina’s tobacco growers to get into,” Nauhaus partner Tim Callahan told the Citizen-Times. “Bringing this in from England is probably not the greatest idea (economically). If local farmers can benefit from this, it would be great for them and great for the economy.” Source.

November 22, 2009 – Leave it to Asheville N.C. to be the first place in the country to build not just one, but two houses largely out of hemp.

Well-established as a green building center, Asheville has two homes under construction – one in West Asheville, another off Town Mountain Road – that use hemp as a building material. The builders and Greg Flavall, the co-founder of Hemp Technologies, the Asheville company supplying the building material, maintain that they’re the first permitted hemp homes in the country.

“This area is known to walk the talk of being green,” Flavall said, adding that the Asheville area has by far the largest percentage of Leadership in Energy and Environmental Design, or LEED, builders of anywhere in the country. Hemp is derived from the same plant that marijuana comes from. Although it contains very little of the active ingredient that gets people high and is completely impractical to smoke, it’s still illegal to grow it domestically.

But builders can import industrial hemp products like Tradical Hemcrete, the material Hemp Technologies sells. When mixed with water and lime, it makes remarkably strong, resilient walls. Some builders generically refer to the walls as hempcrete.

Clarke Snell, of the Nauhaus Group, a collaborative of local companies building the West Asheville home at 67 Talmadge St., describes the resulting structures as “forever” walls. Should you take a wall down, the hemp inside is also reusable.

“Basically, the only thing that can tear this wall down is water,” Snell said, adding that it would have to be a steady stream.

Flavall said the last study done in Europe puts the life span of hemp walls at 700-800 years.

“And even at the end of that, you can use it as fertilizer on a field,” he said.

How it works

The hempcrete mixture starts with 55-pound bales of Tradical Hemcrete brand hemp shiv, or ground-up hemp plant stalks. Workers mix it into a standard concrete mixer, four parts hemp, one part lime and one part water. They pour the resulting slurry into small containers and then pack it between plastic forms that raise a wall two feet at a time. The walls are built around standard stick-built framing.

It takes about a day for a wall to dry and about two weeks before it’s ready for exterior or interior coatings of lime stucco or plaster. Even with those coatings, the material still breathes.

“One of the main reasons I was drawn to the lime and hemp mixture is the breathability – there’s no mold, no mildew,” said Anthony Brenner, whose company, Push Interior/Architectural Design + BuildTechnologies, is building the Town Mountain home. “The lime is constantly taking in carbon, so it’s carbon-negative.”

Hempcrete is also a natural deterrent to insects, and it’s extremely fire-resistant, mainly because of the high lime content. It takes about 2 acres worth of hemp to do one house.

Cost calculations

Hempcrete is more expensive upfront than traditional building materials, mainly because of the shipping costs. Flavall says his company has to import it from Europe, which about doubles the cost.

For the Town Mountain home, he’ll use about 1,875 cubic feet of hempcrete, at a total cost of about $56,250.

That’s higher than typical construction, but Flavall says you’ll net a 30-40 percent reduction in framing costs because less lumber is needed. You also have the potential for a lighter foundation because the hempcrete walls are lighter. Also, homeowners may be eligible for a 10 percent reduction in insurance rates because the product is so flame-retardant.

Nauhaus partner Chris Cashman points out another major advantage: “With this, it’s your Sheetrock, insulation and Tyvek (moisture barrier) all rolled into one.”

Calculating the cost of a Hempcrete home gets complicated.

“We think we can build a house like our prototype for anywhere from parity for a high-end custom home – think Biltmore Village – to 5-15 percent more for a typical home,” Snell said. “However, that’s not the point because construction cost is not your monthly cost.”

He points out that a typical homeowner’s monthly home costs include the bank mortgage, utilities, maintenance, insurance and more. If you’re building a house that uses 15 percent of the energy of a conventional home, then you can take money saved on utilities and put it into construction and end up with the same monthly cost.

“Our mission is to provide carbon-neutral housing for the same monthly cost as a typical home,” Snell said.

Tim Callahan, another of the Nauhaus partners, puts it this way: “The reason it begins to be affordable is because we’ve reduced the energy loads so much.”

The costs over the long haul should appeal to the green-minded.

“The bottom line of this and a traditional house is it’s about cost-neutral,” Brenner said.

Labor-wise, it’s quicker to put up the hemp and plaster than all those other materials like Sheetrock and insulation. Brenner said it will take them about a week to get all the hemp walls up. The Nauhaus guys have put up a test wall and are waiting on the plastic forms from Brenner to do all their walls.

Model efficiency

The house Brenner is building will have 12-inch thick walls, while the house on Talmadge Street will boast 16-inch thick walls and will be 80 percent more efficient than code requirements – so efficient that Snell claims it could be heated solely by the body heat of 18 people.

Besides hemp walls, the 1,450-square-foot, four-bedroom house will have solar panels on the roof to generate enough electricity to power the home, with a surplus. It will have an earthen exterior made from the soil on site, rainwater gathered from the roof and a mostly edible landscape.

The home will be a prototype that the Nauhaus group will use for tours and education.

The house will be owned by the Nauhaus Group itself, although chief engineer Jeff Buscher and his family will live it for two years before it’s sold to allow for energy-efficiency analysis and other research.

Brenner is building the 3,100-square-foot Town Mountain home for Russ Martin, a former Asheville mayor and retired stockbroker, and his wife, Karen Corp. “We’re not afraid of trying something new,” Martin said. “We’ve always been adventurous that way, and this looks like it’s going to work out really well.”

Snell stressed that getting the Nauhaus going has involved a massive, collaborative effort involving multiple local companies.

Based in Asheville, the project is led by Think Green Building, Eco Concepts Development, Eco Concepts Realty and Green Plan.

Both Brenner and the Nauhaus partners want to expand hemp building far and wide.

Brenner said he’s working on a commercial project in Maggie Valley and another home in the Leicester area.

And they’d love to see farmers have a chance to grow hemp legally.

“Our feeling is: What a great crop this would be for North Carolina’s tobacco growers to get into,” said Callahan, the Nauhaus partner. “Bringing this in from England is probably not the greatest idea (economically). If local farmers can benefit from this, it would be great for them and great for the economy.”

Still, as Snell puts it, right now “what you have is a product that you can’t grow but you can buy” in the United States.

Brenner thinks the technology will take off when potential homeowners and developers come to understand its advantages.

“We’ve been seeing interest from all over the country,” Brenner said.

“People are truly interested in green construction and green building, and I don’t know how much more green you can get than this.”

Flavall said another hemp house will start up next year in Franklin, and he’s receiving strong interest in other projects.

“I’m seriously of the belief that we’re making history here,” he said.

By John Boyle Source. On the Net:

November 20th, 2009 – U.K. – A house built from straw-bales and panels of hemp has passed an industry standard fire safety test which exposed it to temperatures above 1,000C.

BaleHaus@Bath is part of a new research project at the University of Bath into how renewable building materials can be used for homes of the future.

The house is made from prefabricated cells of timber filled with straw or hemp, rendered with a lime-based coat.

During the fire resistance test for non-loadbearing elements, the panel had to withstand heat for more than 30 minutes. After more than two hours it had still not failed.

A panel had previously been put through structural tests for loadbearing elements and had passed.

Researchers Dr Katharine Beadle and Christopher Gross, from the University’s Building Research Establishment Centre in Innovative Construction Materials, will be monitoring the house for a year.

They will be checking its insulating properties, humidity levels, air tightness and sound insulation qualities to assess the performance of straw and hemp as building materials.

The technology was used last year to build an eco-friendly house in six days for the Grand Designs Live exhibition.

“I expect the results will show people that we can minimize the use of highly processed materials in building and genuinely make use of such sustainable building materials,” he said.

“It’s vital that we encourage people to recycle, insulate and minimize the use of fossil fuels to keep our buildings warm.”

The ModCell BaleHaus system has been created by White Design in Bristol and Integral Structural Design in Bath. Source.

November 18, 2009 – A visit to the Innovation Park at BRE in Watford has been arranged as part of the Natural Fibres 09 conference, which takes place at the Institute of Materials, Minerals and Mining in London from December 14-16.

The park showcases modern methods of construction and features over 200 different emerging technologies in a number of demonstration properties, including the Renewable Hemp House.

Speaking at the 60th annual congress of CELC – the European Confederation of Flax and Hemp – which took place in Strasbourg, France, from November 4-7, Claude Eichwald of French organisation Construire de Chanvre, said that the use of hemp in concrete was growing, with between 2-4,000 houses now constructed completely from hemp concrete, and many more employing it with mixtures of other building materials. The CELC conference also heard from Rémi Perrin of Strasbourg-based Soprema, which is now manufacturing flax roofing membranes, and Vincent de Sutter of Sutter Freres which has been making natural-fibre based door panels for almost 50 years.

In the latest copy of its journal, CELC outlines the components of a house entirely constructed from natural fibres, as show in the illustration above.

The unique energy efficient house made from hemp at the UK BRE Innovation Park meanwhile, showcases the future of low carbon and sustainable buildings.

The three bedroom Renewable House, which costs £75,000 to build (not including ground works or utilities), uses renewable materials to deliver a well designed, yet low cost, affordable home.

The external walls are constructed from Hemcrete, provided by manufacturer Lime Technology, made from hemp plants grown and harvested in the UK and lime based binder.

It is estimated the carbon footprint of this house will be around 20 tonnes lower than a traditional brick and block house. The hemp absorbs around five tonnes of carbon dioxide from the atmosphere during its rapid growth period, which then becomes locked into the fabric of the building, making the thermal Hemp-Line walling solution ‘carbon negative’.

November 17, 2009 – Investing adequately in agriculture can lead to permanent structural transformation and hunger alleviation in Africa. Not only is the food system a major employer of the poor, but it also generates the capital and demand for expansion in non-agricultural sectors.

Consider the large scale growing of Hemp. The US Hemp food sales are experiencing an annual growth rate of 50% according to the US industry research group SPINS. China whose trade GDP quadrupled in 20 years exports Hemp that is grown on its 800,000 acres. Think of how much more Africa could grow.

Hemp is a crop that is multi-beneficial, and a strong step to creating productive, healthy and even prosperous conditions in Africa. Hemp has up to 25 000 potential uses. It is a high plant protein source and can be pressed into nutritious oil essential for our immune system and clearing the arteries of cholesterol and plaque.The oil from hemp seed can be sprouted (Malted) or ground and baked into cake, bread, and casseroles.

Hemp is an environmentally sustainable, economically viable “ancient wonder crop”. Farmers around the world grow it without the use of pesticides or herbicides. Hemp is earth’s number-one biomass resource. Biomass can be converted to methane, methanol, or Gasoline at a cost comparable to petroleum. It can produce 10 times more methanol than corn. The use of hemp fuel does not contribute to global Warming.

One acre of hemp can produce as much usable fiber as four acres of trees or two acres of cotton. Trees may take several years to grow, while hemp can be cultivated in as little as 100 Days and can yield much more paper than tree.

Until 1883, from 75-90% of all paper in the world was made with cannabis hemp fiber. Hemp paper is longer lasting than wood pulp, stronger, acid-free, and chlorine free.

Hemp can as well be a textile solution for Africa as it is softer, warmer, more absorbent and has three times the tensile strength. About 70-90% of all rope, twine, and Cordage was made from hemp until 1937. Hemp withstands heat, mildew, insects, and is not damaged by light. Oil paintings on Hemp and/or flax canvas have stayed in fine condition. Hemp fiber has strong, rot resistant carpeting potential eliminating the allergic reactions associated with new synthetic carpeting.

An acre of full Grown hemp plants can sustainably provide from four to 50 or even 100 times the cellulose found in cornstalks, or sugar cane (the planet’s next highest annual cellulose plants). One acre of hemp produces as much cellulose fiber pulp as 4.1 acres of trees, making hemp a perfect material to replace trees, for pressed board, particle board, and concrete construction molds.

Heating and compressing plant fibers can create practical, inexpensive, fire-resistant construction materials with excellent thermal and sound insulating Qualities. These strong plant fiber materials could replace dry wall and wood paneling.

William B. Coned of Condi’s Redwood Lumber,Inc., in conjunction with Washington State University (1991-1993) demonstrated the superior strength, flexibility, and economy of hemp composite. Archeologists have found a bridge in the South of France from the Merovingian period (500-751 A.D.) built with this process.

Hemp is a wonder plant that Africa should consider growing as a strategy to create wealth for the continent.

Please also see:
Can Hemp Products Save the World?
Canada – Hemp Bringing Highs to Farmers’ Lows

November 10, 2009 – The demand for more environmentally-friendly building materials and techniques is at an all-time high and will, in all likelihood, only continue to increase. Since buildings account for 38% of the total carbon dioxide emissions in the U.S., it’s obviously time for us to take a step back and rethink the way our buildings affect the environment. Among the new, greener building materials and techniques is a material that’s not so much new as it is rethought: hemp.

hemcrete-brick

We have, of course, known about and used hemp for thousands of years. It’s one of the oldest known cultivated crops, and it can be used for everything from textiles to paper to food and beyond. It’s also extremely renewable, with crops maturing after just 14 weeks. And now, you can make buildings out of it. Tradical Hemcrete is a fascinating material designed by UK company Lhoist, made of hemp held together with a lime-based binder. It’s durable, strong, just as easy to use as conventional building materials, and actually good for the environment.
hemcrete-carbon-negative-building-material

Not only is Hemcrete carbon neutral; it’s actually carbon negative. CO2 from the atmosphere is trapped in the hemp plants as they grow, and remains there after the plants are harvested. During their grow cycle, the plants also release oxygen into the atmosphere. Even when combined with the lime binder, the overall product takes more CO2 out of the atmosphere than it puts into it.

hemcrete-environmentally-friendly-building-material

As if that weren’t enough to make the construction industry take notice, Hemcrete is also recyclable. When a Hemcrete building is torn down, the remnants can amazingly be used as fertilizer. And this isn’t one of those great ideas that’s completely impractical to use, either – the material is fireproof, waterproof, a great insulator, and resistant to rotting (as long as it’s above ground), making it a viable choice for any number of construction applications.

hemcrete-hemp-building-material

Unfortunately, because the species of hemp used in Hemcrete is illegal to grow in the U.S., it’s not yet widely used here. The construction industry is feeling increasing pressure to green up their practices, though, and Hemcrete is finally available in the U.S., though not without a significant cost. Hopefully this will change as the government seeks to open up new avenues to climate change.

November 7, 2009 – Assess for us, if you would, the qualities of this sustainable construction material:10169742-hemcrete-block

* Bio-negative manufacturing (more carbon dioxide is locked up in the process of growing and harvesting the component materials than is released during the production of the binding ingredient)
* 100% recyclable (can be used as fertilizer after being demolished)
* Waterproof
* Fireproof
* Insulates well
* Does not rot when used above ground

What is this mysterious construction material, and why isn’t it in your home? The material is hemp, and it’s not used in the United States because of laws prohibiting growing of so-called industrial hemp. Hemcrete bricks, made from hemp, lime and water, have been used in Europe for years now. Growing hemp—even low-THC varieties specifically raised for food, fiber and industrial use—is illegal in all but a handful of states in America, making construction with sustainable hemp bricks prohibitively expensive. Figures from the Hemp Industries Association show that virtually 100 percent of the hemp used in American hemp products last year—products worth approximately $360 million in retail value—were imported.

Progress toward legalizing industrial hemp farming in the United States is crawling. Oregon recently became the ninth state to remove legal barriers to industrial hemp farming. Reports StoptheDrugWar.org:

Hemp is a member of the cannabis family, but is distinguished from smokeable marijuana by its low THC content and its lanky, fibrous appearance. The Oregon law specifies that industrial hemp must contain less than 0.3% THC. So does pending federal legislation, HR 1866, sponsored by Rep. Ron Paul (R-TX), which would remove low-THC hemp from the Controlled Substances Act and thus the DEA’s domain. The eight other states that have removed barriers to hemp production or research are Hawaii, Kentucky, Maine, Maryland, Montana, North Dakota, Vermont and West Virginia. Oregon joins North Dakota as the only states that do not require farmers to obtain federal permits from the DEA to grow hemp. By Lisa Poisso. Source.

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