Frequently Asked Questions

Why hemp?

Hemp building materials are made from the woody core and fibre of the hemp plant with lime. We make two things: hemp fibre insulation for timber frames, and hemp lime blocks for walls. They lock away carbon as they are made, breathe to manage moisture, and keep indoor air healthy. We are on a journey to circularity and robust buildings.
Hemp blocks are air-dried blocks of hemp bound with a lime-based binder. No cement, no plastic, nothing toxic. The hemp stores carbon it drew down while growing, and the lime keeps absorbing carbon as it cures. They are non-structural and work with a supporting frame.
A hemp wall does not just resist heat, it stores and slows it. At 110mm the block reaches about R1.59, roughly eleven times the R0.14 of a clay brick of similar thickness. With its mass, this flattens temperature swings so rooms stay even through the day.
Hemp walls are vapour open. They let moisture move through and release rather than trapping it. This helps hold humidity in the comfortable 40 to 60 percent range, discourages mould, and protects both the building fabric and the people inside.

The density and mass of hemp blocks absorb sound rather than reflect it. A twin-leaf hemp wall reaches around Rw 56 in lab testing, enough to noticeably quiet traffic and neighbour noise. Field and width-specific figures are being confirmed.
Hemp materials are among the few that can be carbon storing. Our 200mm block holds a verified Environmental Product Declaration of about minus 6.7 kg CO2e per square metre, meaning it locks away more carbon than its manufacture emits.
Blocks come in a range of widths, each giving a different R-value, from slim internal-leaf blocks to thick single-skin blocks. You pick the width for the wall's job: internal comfort layer, insulated veneer, or full single-skin wall.
Hemp is an unwelcoming home for pests. Blocks and renders are lime rich and strongly alkaline, which rodents and insects avoid. The hemp is locked in a mineral matrix, so there is no soft nest and no food value. The wall stays dry rather than damp, and a solid block wall has no stud cavities to nest in. Mice, rats, cockroaches and termites tend to look elsewhere. Strong deterrence, not a guarantee. Founder note (a builder and a mum, not a lab): our hemp fibre has sat in a shed four years, untouched by pests.

How do you build with it?

Hemp blocks are non-structural. They work as a high-performance insulating and finishing wall around a timber or steel frame that carries the load. This keeps the engineering simple and certain.
Hemp block takes breathable finishes inside and out. Inside: clear coat for natural texture, lime wash for subtle colour, or full lime render for a smooth modern look. Outside, a breathable lime render is required, to protect the wall while letting it regulate moisture and temperature. Every finish stays vapour open, which prevents trapped moisture.
Yes. Our wall build ups run a drained and vented cavity between the frame and the outer leaf, with a Class 4 vapour open membrane on the frame. The cavity takes up movement, drains any water, and carries the wall through the tougher climate zones on condensation. Detail is set per assembly and drawn up. We hold 14 wall assemblies plus four ceiling, four roof and four floor assemblies, spanning climate zones and building classes 1 to 3, inner city to rural.
Openings are flashed with breathable membranes carried into the cavity, so water is shed outward while the wall stays vapour open. Detailed drawings are available.
Yes. A thermally broken, insulated slab pairs well with hemp walls. Edge insulation stops the slab bridging heat, so the wall's comfort benefit is not lost at the floor.
On a lightweight timber-framed home like a Queenslander, hemp blocks work as a reverse block veneer: the mass sits inside the frame where it steadies indoor temperatures.
A hemp wall weighs about 38 kg per square metre against roughly 198 for brick, so it is far lighter on the structure. Openings still need a lintel or support over them.

No plasterboard needed. The rendered or natural block face is the finished internal surface, which removes a trade and a material from the build.
Yes. A rendered hemp wall can be made airtight while staying vapour open. Airtightness is handled at a dedicated membrane layer and at junctions, then confirmed with a blower door test.
A Performance Solution is a code pathway where we back the wall with test evidence rather than a standard recipe. We provide the data and support your certifier through it, with CodeMark certification underway.
For walls above about 4.5 metres, or for multi-storey work, blocks are detailed with engineered support. Being non-structural, they always work with the frame.
In wet and tiled areas the tiling is carried on a waterproofed stud frame, with the hemp wall providing the surrounding comfort layer.
Hemp blocks cut with hand tools and are light to lift, so they suit hands-on builders. Some certified systems require a trained installer to hold their rating.
Yes. On a structurally sound wall, hemp blocks can be added to lift thermal and acoustic performance, tied back with the appropriate connectors.

How does it perform?

Heavy items like split systems, cabinets and large TVs are fixed with the right anchors, or to a backing fixed to the frame behind the block.
Replace the internal brick skin with hemp block and you gain comfort, efficiency and robustness. Brick and concrete store heat but insulate poorly, running cold in winter and hot in summer without constant heating and cooling. Hemp block pairs mass with insulation in one layer, holding a steadier temperature and buffering humidity, while the outer masonry keeps doing its structural job. Independent reverse veneer research shows hemp reaching comfort faster and holding it on less energy.

Hemp suits all common floor types. Concrete slab brings high thermal mass for passive solar and cooler climates. Timber or steel on stumps suits sloped or flood prone sites and carries lower embodied carbon. We supply the floor and subfloor assembly for each, detailed to manage moisture and hold thermal performance, and hemp blocks or batts can insulate the subfloor in bearer and joist builds.
Hemp fibre batts are the best pairing for thermal and moisture performance. They buffer and release moisture, so they keep their R-value where synthetic batts fail when damp. Stable, they resist sagging for years. Conductivity around 0.039 W/mK, on par with glasswool and rockwool, and no skin or lung irritation to install. A healthier batt that vermin dislike, so mice, rats and cockroaches stay out.

What does it cost – and is it worth it?

Hemp block R-value rises with width, tested to EN standards: about R1.0 at 70mm, R1.6 at 110mm, R2.9 at 200mm, up to R4.6 at 320mm. New EU verified testing is underway that could almost double these, treating the block as an insulation product; we will publish once verified. R-value is only part of it, mass and breathability do the rest.
A hemp wall uses fewer blocks, weighs less, and needs no plasterboard, which offsets part of the cost. It is best compared on comfort, health and lifetime value, not build price alone.

For a single-skin wall the mass belongs on the inside, a reverse block veneer, so it steadies indoor temperatures rather than heating up outside.
More is not always better, and that surprises people. Every extra layer of insulation saves less energy than the layer before it, so the early thickness does most of the work and the later thickness costs more while returning less. There is a carbon cost to weigh as well. Making insulation takes energy, so past a certain point the extra material has released more carbon than the extra insulation will ever save back. A UK industry body, the Alliance for Sustainable Building Products, published a briefing paper on exactly this question in June 2024, called Insulation and retrofit: finding the sweet spot. It is good thinking and it is where our products live. We are not going to quote its numbers at you, because they rest on the UK building code, UK housing stock and a heating dominated climate, and Australia has none of those three. So the honest position is that the principle holds here and the numbers do not, and nobody has published the Australian answer. We are working with academics to start that research. In the meantime we size the insulation for your climate zone and your wall, and we tell you when adding more stops being worth it.

Carbon, testing and transparency

Hemp blocks are naturally fire resistant, tested at reaction to fire B-s1,d0 with strong fire resistance results. A hemp block single-skin system already holds CodeMark certification from BAL 12.5 to BAL-FZ, which shows the pathway into bushfire zones exists. We are completing our own bushfire testing.
Yes. Our 200mm block holds a registered Environmental Product Declaration at about minus 6.7 kg CO2e per square metre, valid to 2029. The insulation EPD is in verification.
Backed by independent European test reports for the blocks: reaction to fire and fire resistance (EN), thermal conductivity and resistance (EN), compressive strength and density (EN masonry), acoustic absorption and sound reduction (ISO), and vapour resistance (ISO). Hemp insulation adds a BBA certificate. The 200mm block holds a verified EPD to EN 15804. Durability comes from the lime binder and a breathable wall. Australian testing is underway toward CodeMark.
Our carbon figure comes from sequestration, not bought offsets. The hemp stores carbon drawn from the air, counted in a verified EPD to EN 15804, not from carbon credits.
This is where hemp wins. Price aside, one hemp wall does what several products usually do: insulate, add mass, breathe, resist mould and vermin, perform on fire and acoustics, and store carbon rather than add it. No conventional wall multi-solves like this. Hemp lime building has stood for more than three hundred years, and it is circular: blocks return to soil at end of life, with batts to follow once the biogenic binder is cracked. Measure everything but cost and hemp comes out ahead.
Architects and specifiers get sample boards, technical data sheets marked verified or estimated, an assembly and detail library, European test reports and the block EPD, plus specification support on live projects. Studio CPD, lunch and learn sessions and formal training are planned as interest grows, led by the construction experts in our crew.

Hemp is our focus and our strength. We work the whole wall envelope in hemp, with hemp lining boards and a non-structural hemp timber-type product joining the range and a hemp rain screen in R&D, without diluting what hemp does best.
Not just new homes and retrofits. Hemp suits apartments, schools, aged care, hospitals and other commercial buildings, and potentially data centres, anywhere you want a robust, healthy building that stores carbon rather than adds it. These are markets we are actively working towards.
We’ll be straight about it. For now, our blocks and insulation are imported, just like a lot of building materials used in Australia.
Shipping adds carbon, and the number changes with the vessel, route, packing and road freight at this end. We’re working through that with our shipping agents and will publish it alongside the manufacturing figures when it’s ready.
Importing now helps us build the market and fund the next step: local hemp processing and block manufacturing at Barham in NSW, backed by a NSW Government grant.
It also means we’re not starting from scratch. The products already come with European declarations, test reports and certification. We can build on that evidence, add Australian testing, and progressively move more of the range to Australian-grown and Australian-made.
Our published block figure is –0.880 kg CO₂e per block, or about –6.7 kg CO₂e per square metre of wall, cradle-to-gate. That covers growing and harvesting the hemp, making the lime binder, transport to the factory and manufacturing the block.
It does not include shipping to Australia, delivery to site, installation or the use stage. Shipping is a real carbon cost and varies by route, vessel, packing and road freight, so we’re calculating it separately rather than publishing a generic number.
At end of life, the block declaration models landfill, which means the stored plant carbon is counted as released again. There is not yet an established recovery pathway.
So the short version is: the block stores carbon while it is in the building, the delivery footprint is still being quantified, and end of life remains a gap the industry needs to solve.
Insulation is one layer among many, so swapping it alone rarely decides the whole result. It does move the number a long way though, because you are replacing a material that costs carbon to make with one that stored carbon while it grew. Australian modelling of three house designs, done at a university this year, shows the swap cutting whole building embodied carbon substantially in every one of them, and the lighter the building the bigger the shift. Whether a building tips all the way past zero depends on everything else in it, the frame, the floor, the cladding and the finishes. We are not publishing a figure from it yet. Two of its inputs are being corrected, one of the material figures and one of the electricity grid factors, and until that is done and the work is independently checked the result is not ours to quote. When it is confirmed we will publish it whatever it says.
There is no single number, and that is the honest answer rather than an evasion. Freight carbon moves with the vessel and its size, the route it takes, how full the container is, how the product is packed, which ports and depots it passes through, and how far it travels by road once it lands in Australia. Those things change from shipment to shipment, which is a large part of why so few building products publish a delivery figure at all. We arrange the shipping ourselves, so these are things we can influence rather than only report, and we are working the figure through with our shipping agents rather than publishing one we could not stand behind. Two things we can tell you now. Per tonne carried per kilometre, road freight is several times more carbon intensive than sea freight, so a long Australian road delivery can rival the ocean voyage that brought the material here. And where your site sits relative to the port genuinely matters to the delivery footprint, which is one more reason we are building manufacture at Barham. When we hold the number we will publish it with the route and the assumptions stated beside it, whatever it says.

Sticky questions no one usually answers

Both products, in full, by weight. A hemp lime block is about 31 percent hemp shiv and 69 percent lime binder. Hemp fibre insulation is about 90 percent hemp fibre, 9 percent polymer binder to hold the fibres together, and 1 percent of a salt that acts as a fire retardant. That is the whole list. Both products have been checked against the European register of substances of very high concern, and neither contains any of them above the reporting threshold. If you want the paperwork behind that, ask us and we will send what we are allowed to send.
Because without it the batt falls apart. About 9 percent of the insulation by weight is a polymer binder that holds the hemp fibres together and gives the batt the rigidity to sit in a frame without slumping. We would prefer to build the batt without it. It is the reason the batts are not yet circular, and it is the thing we are working on. We are telling you because it is in the declaration and you are entitled to know it.
No, and this is worth two minutes because it is the most misunderstood thing in our category. A material on its own gets one classification. The finished wall it sits in gets its own, usually higher, because the lining and the build up add protection. Our hemp fibre insulation on its own sits in a lower band. The same insulation inside a complete lined wall, tested as a system, reaches a much higher one. Hemp blocks carry their own classification across every width. Then there is a third thing again, fire resistance, which is how many minutes a wall holds back a fire, and that only ever belongs to one specific tested build up. So if someone quotes you a fire number, the useful question is always: is that the material, the system, or the resistance, and which exact wall was tested?
The hemp itself does not. Both manufacturers state that once the products are installed and protected by the rest of the wall, they need no maintenance and no replacement for the life of the building. What does need looking after is the render on the outside, because that is the layer protecting everything behind it. Treat it the way you would any rendered wall. Keep an eye on it, repair cracks, and use breathable products when you do. Get that right and the wall behind it looks after itself.
Hemp handles humidity far better than most people expect. It should still be kept out of the rain. The insulation has been tested for mould resistance through four straight weeks at 98 percent humidity and passed, which is a far wetter condition than any building site in an Australian winter. That is a laboratory test. It says nothing about a stack of material sitting in a downpour. The practical rules are simple. Store blocks indoors and ventilated until you lay them. Get the roof and the waterproofing on before you build the walls, which is the sequence the manufacturer specifies anyway. And if hemp fibre does get damp, it dries out and keeps its shape. We have watched that happen in a bucket.

Often not. Environmental declarations are only comparable when they are built the same way: the same category rules including the same version, the same unit being measured, the same stages counted, the same cut off rules, and both still valid on the day you compare them. Change any one of those and the two numbers are measuring different things. Our own declarations say this on the page. So when you are weighing us against something else, check what stages each figure covers and what unit it is per, before you compare the numbers themselves. We will help you do that even when it does not flatter us. There are numerous committees that sit and deliberate over carbon accounting methods and harmonisation. It is a bit like COP: nobody fully agrees, words matter, they carry impact, and they hold varying definitions. So we present ours as plainly as we can.
Longer to make than you would think, and quicker to get than you would think. A hemp lime block is cured, and the curing is the slow part. After it is pressed it matures for about two months to build strength, then sits in storage for around six more, and during that whole time the lime is still pulling carbon dioxide out of the air and hardening. That patience is part of why the carbon figure is what it is. The upside for you is that the material is cured before it ships, so you are not waiting on curing once you have ordered. Lead times depend on stock and shipping on the day, so ask us and we will give you the current position rather than a general one. On site there is one waiting period worth planning for: leave at least fourteen days after the mortar sets before you render.
Quite a few things, and here they are. We do not yet have an Australian bushfire attack level rating, and until we do we will not imply one. Our Australian testing programme is scoped but has not started, so most of our performance figures currently come from European testing and we say so every time. We do not yet know what shipping the material to Australia costs in carbon. We have learned it is a variable rather than one number, so we are working it through with our shipping agents to get it right, and we will publish it when we hold it regardless of what it says. Only one block width currently holds its own verified carbon declaration; the others are labelled indicative until they do. And our insulation declaration has expired and is being renewed. None of this is comfortable to write. We would rather you had it.
Because we publish what the evidence says, and evidence moves. The density of our blocks was restated by the manufacturer this year, which changed every weight we quote. New thermal testing is running in Europe now. Our insulation declaration expired and a new one is being verified. Each time something moves we update the figures and tell you what changed. Ours move because we keep checking them. We would rather hand you a number that changed last month than one that has not been looked at since the day it was written.

What does all the technical stuff mean?

How well a layer resists heat passing through it. Higher is better. It is the number building codes set minimums against, so it is the one your designer or assessor will quote back at you. WHEN COMPARING: an R-value means nothing without a thickness beside it, because R rises as a material gets thicker. Also check whether you are being given the R-value of the material alone or of the whole wall including linings, cavities and framing. Those are very different numbers and the wall number is the one the code cares about.
The other way of saying the same thing. It measures heat lost through a whole element rather than resisted by it, so lower is better. R and U are inverses of each other. Used more in Europe than in Australia. WHEN COMPARING: check what layers are included, because a U-value for a bare material and a U-value for a finished wall are not the same claim.
The raw rate at which a material conducts heat, written in W/mK. Lower is better. Unlike R-value it does not change with thickness, which makes it the fairest way to compare two materials against each other. WHEN COMPARING: lambda is measured at a set average temperature, and the European and Australian test standards use different temperatures. The same material can honestly be quoted two slightly different ways depending on which standard the test was run to. Ask which one.
How freely water vapour can pass through a material so a wall can dry out. It has nothing to do with draughts or air leaking. A breathable wall lets moisture move through and escape instead of trapping it where it can cause damage or mould. WHEN COMPARING: breathable is used very loosely in marketing. It only means something if there is a mu or an Sd number behind it.
How much harder it is for vapour to pass through a material than through still air. Still air is 1. A material at 5 is five times more resistant than open air. Lower is more breathable. WHEN COMPARING: it is a property of the material, so it does not tell you how the finished wall behaves until you know how thick each layer is. That is what Sd is for.
Mu multiplied by thickness, expressed in metres. It converts a material property into something practical, because a thin layer of a resistant material can behave much like a thick layer of an open one. It is the number used to classify membranes. WHEN COMPARING: a lower Sd means more open. If a wall build up is described as breathable, the Sd of the layers is where you check it.
How much a material itself contributes to a fire, graded A1 for non combustible down through B, C, D, E, to F. F does not mean it burns fiercely; it means no performance was determined. The letters are usually followed by a smoke rating, s1 to s3, and a flaming droplets rating, d0 to d2. WHEN COMPARING: this is the single most misread number in building products. A class can belong to a product on its own, or to a complete tested wall including its linings. The same material can be one class bare and a much better class inside a tested wall, and the two are not interchangeable. Always ask which one you are being shown.
How long a built assembly holds back a fire, measured in minutes. This is always a property of the wall, never of a material on its own. Australia writes it as an FRL, three numbers in minutes for structural adequacy, integrity and insulation, like 60/60/60. Europe writes it as EI followed by minutes. WHEN COMPARING: a European EI result and an Australian FRL are not the same test and do not convert. A certifier will not accept one in place of the other.
A single number for how much sound a wall stops. Higher is better, and roughly every extra 10 dB halves how loud something seems. Ctr is a correction added for low, rumbling noise like traffic, so Rw plus Ctr is the harder and more realistic figure for a wall facing a road. WHEN COMPARING: Rw belongs to a whole tested wall build up, never to an insulation or a block on its own. Also check whether the number is a laboratory result or a measurement in a finished building, because real buildings always perform below the laboratory and the gap comes down to detailing and workmanship.
The American equivalent of Rw. Same kind of measurement, different frequency range and a different penalty rule. WHEN COMPARING: you cannot convert one to the other from the single number. It needs the full set of underlying frequency readings to be re-scored. If someone hands you a converted figure without the underlying data, be sceptical.

Mass in a wall soaks up heat and releases it slowly. Thermal lag, in hours, is how long heat takes to work its way through. A long lag means afternoon heat arrives inside in the evening, softened, instead of at the hottest part of the day. WHEN COMPARING: lag is genuinely useful where days are hot and nights are cool, and much less useful where it stays hot overnight. It is a comfort property, not an insulation property, and a material can be good at one and poor at the other.
The carbon emitted, or stored, in making a product, separate from the energy the building uses once people move in. Written in kg CO2e. A negative number means more carbon is held in the material than was released making it, which plant based materials can do because the plant took carbon out of the air as it grew. WHEN COMPARING: two embodied carbon figures are only comparable if they cover the same stages. That is what the next entry is about, and it is where most comparisons quietly fall apart.
The stages from growing or mining the raw materials, through transporting them to the factory, to the finished product leaving the factory gate. It does not include getting the product to site, installing it, maintaining it, or what happens at the end of the building's life. Those stages have their own codes: A4 and A5 for delivery and installation, B for the life of the building, C for end of life, and D for anything recovered afterwards. WHEN COMPARING: most published carbon figures are cradle to gate, and a lot of them do not say so. If a figure has no boundary stated, you cannot compare it with anything. Also worth knowing that A4, delivery to site, is not a fixed property of a product. It changes with the route, the vessel, the packing and the distance from port to site, so two honest A4 figures for the same product can differ a long way from each other.
What the number is actually measured against: one kilogram, one square metre, one cubic metre, or one item like a single block. Every declaration states it near the front. WHEN COMPARING: this is the quiet trap. A figure per block and a figure per square metre of wall can come from the same document and look wildly different. Before comparing two products, check both figures are on the same unit, and if someone has converted one for you, ask what assumption they used.
A life cycle document prepared to an international standard and checked by an independent verifier, then registered publicly. It is not a logo or a self declaration; it is a document with a registration number you can look up. WHEN COMPARING: check three things. Is it in date, since they expire. What stages does it cover. And what is the declared unit. An EPD that fails any of those three cannot be compared with another one, and the standards themselves say so.
Three words that get used as if they mean the same thing. Verified means an independent party has tested or checked it. Declared means the manufacturer has formally stated it, often under a standard, which is stronger than marketing but is not the same as independently tested. Estimated means calculated or engineered rather than measured. WHEN COMPARING: all three can be honest and useful. What matters is that whoever gives you a number tells you which one it is. If they do not say, ask.
The level of bushfire exposure a building has to be designed for, from BAL-LOW up to BAL-FZ for flame zone. It is set by your site, not by the product. WHEN COMPARING: no material is good or bad at BAL in the abstract. What matters is whether the complete wall system has been assessed and is suitable for the level your site is rated at. A certificate held by one company for one product does not carry across to another.
A single carbon number is usually three numbers added together, and the standard requires them to be reported separately as well. GWP-fossil is the warming effect of carbon from fuels, electricity and mineral processes. GWP-biogenic is the carbon a plant took out of the air as it grew, reported as a negative, and released again later. GWP-luluc is land use and land use change: emissions and removals from the soil and the land itself, from ploughing, from clearing, from changing what a paddock is used for. Added together they give GWP-total, which is the figure most products headline. There is a fourth, GWP-GHG, which is GWP-total with the plant's uptake set to zero. WHEN COMPARING: a plant based product and a mineral product can report the same word, carbon, and mean different arithmetic. The plant based figure usually leans on GWP-biogenic and the mineral one usually does not have one. If a published figure does not say which indicator it is, it cannot be compared with one that does.
Both declarations behind our products are European documents. They are written to EN 15804, the European standard, under Product Category Rules issued by the International EPD System, and they use European impact assessment factors and European background databases. Manufacturing electricity is modelled on the grid where the factory sits, so a Portuguese or a Scottish grid rather than an Australian one. Australia has no mandatory equivalent, and Australian declarations are published through the same International EPD System, so the two are readable side by side. WHEN COMPARING: the method travels, the data does not. A product made here on an Australian grid, from Australian feedstock, is a different life cycle even when the recipe is identical, and it needs its own declaration rather than a translation of the European one.

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Frequently Asked Questions