Bill and Anne Smith instructed AECB members, Inspiration Architects of Newbury, to design a smaller house using one of the most environmentally friendly materials available – Tradical® Hemcrete®. This bio-composite building material made from hemp shiv (the woody core of industrial hemp) and a lime-based binder delivers a negative carbon footprint. Supplied by Oxford-based Hemcrete Projects – part of the Lime Technology Group – it also offers a unique combination of insulation and thermal inertia, properties that combine to create buildings with very stable internal environments that require very little heating or cooling.

Three years on the Smiths are still happy. “We have a delightful contemporary home that has been zero carbon from day one, and which has performed better than we expected. Its inherent qualities mean we have a very comfortable and practical house, which never feels stuffy. The walls not only breathe, they allow water vapour to pass through which helps passively regulate humidity and temperature. Not surprisingly, the house remains cool in the summer and warm in the winter.”

The only heating required for the two-storey detached house is a wood-burning stove with back boiler. Whilst a mechanical heat recovery system is installed, in the warmer months the unit is switched off and natural ventilation is all that is required to maintain what the owners describe as a ‘very consistent’ and ‘pleasant’ living environment.

Building using hemp and lime has exceeded expectations when it comes to running costs. With only wood needed to heat the house, and five PV and two solar hot water panels on the south-facing roof, net electricity costs are zero. Skylights above these panels enable heat to be stored in the house’s thermal mass. A rainwater harvesting system for flushing the toilets not only conserves scarce water resources, it also cuts water bills substantially.

Built in the garden of their former home, the new property is two storey, double heighted and glazed at both the east entrance hall and west garden elevations. It is finished with lime render and lime paint on the ground floor – also supplied by Lime Technology – and untreated oak board cladding above, which has been allowed to silver. The house was designed to meet the needs of an older couple with a large living area/kitchen opening out onto a patio, a utility room, shower room and study downstairs. Upstairs are two bedrooms, one with a balcony overlooking the garden, a box room and large bathroom. The downstairs study is designed to convert to a bedroom should mobility become an issue. The timber frame superstructure is echoed by internal oak doors and its extensive glazing makes the house very light. The windows and the glazed folding doors are in oak with a grey powdered aluminium external finish.

Building using a hemp and lime combination creates a substantial smoothing out of temperatures, thus reducing peak loads and the capital costs of an M&E system. The building fabric partially takes over the regulation of the internal conditions using the passive properties of the material, instead of using the active properties of the M&E system. Energy bills are low when compared to the running cost normally associated with a conventional new building, and occupants are quick to point out how much they appreciate the internal environment that building with hemp seems to create, including staying cool during this summer’s heatwave.

In addition to exceeding expectations based on conventional steady state U-values and standard thermal modelling, the process is also negative embodied carbon. This arises due to hemp capturing carbon dioxide during its rapid growth, whilst releasing oxygen back into the atmosphere. The carbon is then locked up within the walls of the building to give a carbon negative solution.

The hemp and lime combination is now available in an “off-site” panel system. These panels are pre-dried in the factory to make the build process faster and easier.

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The Clayton House is our latest project featuring the first Tradical ® Hemcrete® house in Florida. The house, built in a coastal community, will meet all hurricane safety codes. The walls will be constructed using Hemcrete® with a directly applied Baumit Lime Rendered Finish on the outside, and a US Heritage Group lime plaster on the interior walls.

These are revolutionary products to use in a hot, humid climate like Florida because the walls are entirely breathable, unlike commonly used concrete. In a climate like Florida’s, moisture and mold growth in buildings can be a major problem. Cured and dried Tradical® Hemcrete® is a vapor-permeable (Breathable) material that must pass moisture to the internal and external faces of the wall.

Tradical® Hemcrete® is a unique, highly sustainable construction product used to create insulating walls as well as insulation layers for floors and roofs. These products comprise a bio-composite building material that can be used to create buildings that have excellent thermal / acoustic properties as well as creating a healthy living and working environment. Tradical® Hemcrete® is sold in the US by American Lime Technology.

Featured Products

• Tradical Hemcrete
• USHG Lime Plasters
• Baumit Lime Stucco & Plasters

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Have proponents of the tight building envelope got it all wrong? Anthony Brenner and David Mosrie of Asheville, N.C.–based Push Design think so. Their reasoning is that while builders can specify non–off-gassing materials, they can’t control the durable goods (furniture and the like) that homeowners bring in, which may be loaded with chemicals. An air-tight house that uses less energy may do so at the expense of human health, if it has the negative side-effect of trapping harmful toxins inside. Better to build a home that breathes. Asheville’s “Push House” is built with Hemcrete, an eco-friendly compound of industrial hemp, hydraulic lime, and water.

This home is fireproof, waterproof, mold-proof, insect-proof, and gets an “A” for indoor air quality. Its secret? Industrial hemp.

The firm’s prototypical “Push House” offers just such an example. Its stucco-like exterior walls are actually made of 12-inch-thick Hemcrete, a biocomposite masonry compound that’s mold-resistant, bug-proof, and recyclable. And get this: Hemcrete sequesters carbon and other “nasty stuff” from the atmosphere and undergoes a natural petrification process as air filters through it, becoming stronger over time.

Hemcrete’s virtues are well-known in Europe, where it is used for everything from walls to roof insulation, but the Push House marks its first residential foray on this side of the Atlantic. Brenner estimates the cost of each exterior wall at $25 to $30 per cubic foot, but that’s partly because some raw materials had to be imported from the U.K. Domestic production could cut the price tag in half, he says, except for one problem. It’s illegal in the U.S. to grow Hemcrete’s primary ingredient—industrial hemp—which is derived from the stalk of the cannabis plant.

“Right now you can import it but you can’t grow it,” he says. “There’s a stigma that marijuana and industrial hemp are the same thing, but the THC content of industrial hemp is actually only .035 percent.”

Although builder interest in the material is as yet undetermined, there’s no shortage of cash-strapped farmers interested in growing the rapidly renewable plant. In fact, 11 states have approved its cultivation under state law. But the U.S. Drug Enforcement Agency has so far nipped all such enterprises in the bud.

• Cost per square foot to build the nation’s first Hemcrete house outside Asheville, N.C. – $133 per square foot
• Number of years the average Hemcrete building is expected to last – 700 years
• Number of weeks it takes to grow enough industrial hemp on 1.5 acres to build a 1,500-square-foot house – 12 weeks
• Reduction former Asheville Mayor Russ Martin saw in his homeowner’s insurance after moving into the Push House – 60% reduction
• Number of weeks it took to build the shell of this 3,400-square-foot home – 2.5 weeks

Featured Products

• Tradical Hemcrete
• Hemclad Pre-cast Wall Systems
• Hembuild Pre-cast Wall Systems
• Breathe Insulation
• USHG Lime Mortars
• USHG Lime Plasters
• USHG Old World European Limewash
• Baumit Lime Stucco & Plasters

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The brief was to design a small home that would be low maintenance, easy to live in and fulfil highly sustainable criteria. The House, which revolves round a light-filled central atrium for solar gain and light will be build with Tradical^® Hemcrete^®  and feature eco-friendly service products including rainwater harvesting, ground source heat pumps, photovoltaics and low energy lighting. Together with high performance windows, doors and roofing, it will create a zero carbon footprint house.

The lime render finish provides the ideal breathable surface for the high thermal performance of Tradical^® Hemcrete^®. This helps to provide a thermally efficient home from which to enjoy the open southern aspect of this site that provides stunning views through the high performance glazing.

Featured Products

• Tradical Hemcrete
• Hemclad Pre-cast Wall Systems
• Hembuild Pre-cast Wall Systems
• Breathe Insulation
• USHG Lime Mortars
• USHG Lime Plasters
• USHG Old World European Limewash
• Baumit Lime Stucco & Plasters

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Spray application of Tradical® Hemcrete® was specified for this 26 unit housing project with Orwell Housing Association. The Clayfield project is an exemplar for transferable ecological design in social housing, with extremely low embodied CO2 in construction and low energy requirements in use.  As well as having green credentials, it is cost effective to build and contemporary in design. The award winning scheme offers affordable housing with a strong environmental emphasis.

Sustainable Masonry Sets Green Precedent for Social Housing
For the construction of Clay Field’s, 26 new affordable homes for Orwell Housing Association in Suffolk, architects Riches Hawley Mikhail Architects wanted to combine contemporary design, sustainable construction with low energy use and innovative local materials.

To help achieve this, Riches Hawley Mikhail used Tradical® Hemcrete® from Lime Technology. A thermal hemp-lime walling solution that comprises a blend of hemp shiv and a lime based binder, it provides conventional looking wall construction whilst locking up CO2 by capturing carbon from the atmosphere.

Hemp, in common with all similar plants, captures CO2 and releases oxygen during its rapid growth. The immediate and positive effect of this process is the sequestration of the principal greenhouse gas. Furthermore, this captured carbon is then locked into the fabric of constructed buildings. Finally, when the air-lime based binder sets, even more carbon dioxide absorption occurs. In effect, the material becomes better than carbon neutral.

1 cubic metre of Tradical® Hemcrete® wall can lock up 108kg of CO2. At Clay Field’s, it is anticipated the use of Tradical® Hemcrete® will enable the locking up of around 65 tonnes of carbon dioxide.

Product:Tradical® Hemcrete®, Limetec® hydraulic lime mortar and render

Featured Products

• Tradical Hemcrete
• Hemclad Pre-cast Wall Systems
• Hembuild Pre-cast Wall Systems
• Breathe Insulation
• USHG Lime Mortars
• USHG Lime Plasters
• USHG Old World European Limewash
• Baumit Lime Stucco & Plasters

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The Nauhaus is a high performance natural building system that combines the best of cutting edge modern building science with the advantages of traditional building techniques and lifestyles. The Nauhaus system is designed to achieve:

1. A dramatic increase in comfort, long-term affordability, and sensory enjoyment while fostering a healthier lifestyle through an increased connection to nature.
2. Fulfillment of scientifically established benchmarks for residential construction defining a drastic reduction in emissions that contribute to our present global climate change crisis.
3. A solid contribution to a sustainable solution for our present economic crisis by focusing on local materials and workers while creating opportunities for the creation of a variety of local green construction businesses.

The simplicity of the product mixing and placement process allowed the client, friends and colleagues to experience being part of the build team to construct the walls.

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• Tradical Hemcrete
• USHG Lime Plasters

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You can visit the Nauhaus Institute for a detailed exploration of the Nauhaus project.

The cliff top location of this stone faced private house on the Cornish coast provides amazing views across the sea. The client together with Principal Contractor A D Cruize chose to use Tradical^® Hemcrete^® as the thermal walling material to be used in the 6,000 square feet bespoke eco-build.

Most of the solid wall construction was achieved in conjunction with the traditional post and beam timber frame made from local larch wood by building up the external stonework using lime mortar and then casting the Tradical® Hemcrete® between it and temporary internal lightweight shuttering. Other sections of the house have a mixture of timber cladding and lime render external finishes.

Once the building envelope was sealed and in a suitable state for occupation the client chose to move in during autumn, even before the heating system had been commissioned. The performance of the building is such that even with sub-zero temperatures during the winter, the client has found the building to be at a comfortable enough temperature with a minimum of temporary heating input to remain in occupation throughout.

Featured Products

• Tradical Hemcrete
• Hemclad Pre-cast Wall Systems
• Hembuild Pre-cast Wall Systems
• Breathe Insulation
• USHG Lime Mortars
• USHG Lime Plasters
• USHG Old World European Limewash
• Baumit Lime Stucco & Plasters

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For the latest information on projects like this, please contact us.