Advantages and disadvantages of hempcrete

In my view, the advantages of hempcrete far outweigh the disadvantages. If your priority is to build a house as quickly, cheaply and easily as possible, then hempcrete will may not be your material of choice. If you value things like comfort, a healthy home and environmental sustainability, then hempcrete is worthy of serious consideration.

It’s also worth pointing out that a prospective house builder and owner will naturally consider the pros and cons of hempcrete with regard to their own building project. There is however a ‘bigger picture’ which concerns the impact of hempcrete on the wider environment and indeed at a global level.

In compiling this list, I consulted the following books as well as drawing on my personal experience:

  1. The Hempcrete Book, by William Stanwix and Alex Sparrow,
  2. The Whole House Book, by Pat Borer and Cindy Harris, and
  3. The Green Self-Build Book, by Jon Broome.

Advantages of hempcrete as a building material

Feel good factor

I have found that hempcrete buildings naturally exude a ‘feel good factor’ which is difficult to put into words and really needs to be experienced. I would say that they promote feelings of well being, comfort, health and even calmness. The first time I felt this was at French Ecocentre where I visited a small octagonal building made from cast hempcrete. There was nothing inside the building, just bare walls, but I had an instant feeling of “wow, this is amazing”. The reaction of the other visitors suggested they felt something similar.

(I am 100% sure that, if the building been made from concrete blocks, my reaction would have been completely different.)

Years later, my step-daughter’s reaction, upon entering my hemp tiny house after the walls had been built, was the same. Surprise, a big smile and words (in French) to the effect of “oh, this is very pleasant!”

Whether this ‘hempcrete effect’ is due to the hempcrete’s thermal, acoustic or vapour regulating effects, or because it’s a free from synthetic chemicals, or something else – I don’t know. Perhaps one could feel similarly in a house made from straw bales, cob, raw earth bricks or timber.

Thermal performance

Hempcrete was described to me (by a French Eco Builder) as a good compromise between thermal insulation and thermal mass. By varying the amount of lime, relative to the hemp, the insulation value can be adjusted. The greater the proportion of lime, the denser the mix becomes and the poorer it becomes as an insulator. Unlike lightweight insulation, the thermal mass of hempcrete helps smooth out daily temperature fluctuations.

In theory, hempcrete does not insulate as well as some other materials of an equivalent thickness. For example, I found a UK hempcrete block supplier who stated that their 15cm blocks had a U-value (thermal transmittance) of 0.43 w/m2k. By way of comparison I read that a 14cm exterior timber stud wall with mineral wool insulation has a U-value of just 0.29 w/m2k.

In practice however, hempcrete tends to perform better than it should. This is partly due to hempcrete’s combination of thermal mass and insulation and partly due to the effect of water vapour as it moves into, through and out of the hempcrete.

As long ago as 2001, as part of a Suffolk Housing Society development, 2 hempcrete houses were built alongside 2 conventional brick houses and the constructions were monitored and compared. They found that the hempcrete houses maintained an inside air temperature 1-2 deg C higher than the brick built houses.

My own experience of living in the hempcrete tiny house last summer was also positive. After days of hot weather (30-35deg C) the house did get warm inside (but never to the point of being uncomfortable). I remember one evening it was 29 deg C inside the house and in the morning it had descended all the way to … 25 deg C! (the outside temperature would probably have been about 15 deg C). The thermal mass of the hempcrete acted a bit like a storage heater – absorbing the heat during the day and releasing it slowly during the night.

Acoustic performance

The previously mentioned Suffolk Housing study found that hempcrete wasn’t quite as good as a cavity block wall at sound attenuation (I.e. at blocking sound) . Hempcrete was, however, a very good sound absorber. The helped create a comfortable acoustic environment inside the house.

In the Hempcrete Book the acoustic quality of hempcrete is described as “unusual and distinct from that of conventional building materials” and depends on hempcrete’s porosity. It is suggested that the acoustic performance can be varied by the amount and type of binder (lime or cement) in the mix and how tightly the hempcrete is compacted.

It seems to me that hempcrete buildings do have good acoustics but this hasn’t been properly quantified or explained yet.

Vapour permeability

Thanks to it’s porosity, hemp is permeable to water vapour. It is also hygroscopic I.e. it can store and release moisture in the surrounding atmosphere. This is due to the microscopic structure of the cell walls.

The lime binder used in hempcrete is also permeable and hygroscopic (to varying degrees, depending on the lime used).

These characteristics are beneficial to the indoor air quality by helping to maintain a steady humidity and inhibiting the formation of condensation and mould on the surface of walls.

Fire resistance

Pictured is a rocket stove from concrete and hempcrete.  This demonstrates one advantage of hempcrete - it’s fire resistance.
Hempcrete and concrete rocket stove

According to The Hempcrete Book, the French manufacturer Isochanvre has produced test results that indicate hempcrete is a “non-flammable material”.

I can confirm that this is true. As an experiment, I cast hempcrete around some hollow concrete blocks to make a basic wood stove. Despite being in contact with burning wood, the hempcrete didn’t catch fire. Instead it just became progressively more charred and eventually crumbled away.

If you still need to be convinced, there are several videos on youtube of fire tests being conducted on hempcrete, such as this one:

Mechanical strength

Considered as an insulation material, hempcrete is tough and rigid. Compared to regular concrete, hempcrete is significantly less strong (about 1/20 the compressive strength).

However, if a low density hempcrete mix is cast around a load bearing timber frame, the hempcrete itself doesn’t need to have a great compressive strength. However, when fully set, the hempcrete does have a structural role in that it provides racking strength. I.e. it helps the building resist lateral movements. This has the advantage that the number of diagonal braces and horizontal noggins can be reduced or even eliminated completely.

I wish I had known this when I built the tiny house. My carpenter, who helped me frame the building, did a great job. This included diagonal bracing to make the structure nice and rigid. For good measure, I added horizontal noggins right around the building. However, these braces were a real pain when it came to casting the hempcrete around the frame. When I saw how rigid the fully hardened hempcrete was I realised that the braces were unnecessary. If I were to do it again I would suggest some kind of temporary bracing that could be removed in stages as the hempcrete was cast.

Pictured is a timber house frame showing braces and noggins.  An advantage of hempcrete is its rigidity - meaning these braces were probably not necessary.
Tiny house frame showing diagonal braces and horizontal noggins

Resistance to moisture damage

I already mentioned that hempcrete is vapour permeable and can also store and release moisture. This is significant, as water does not get ‘trapped’ in a building’s walls (as it could do in, for example, a timber framed house with a faulty vapour barrier and glass fibre insulation). So, with no trapped water, the timber frame will not rot and the hempcrete can go on absorbing and releasing water vapour indefinitely.

As regards exposure to rain on exterior surfaces, hempcrete is normally protected by a lime render or timber cladding. However, in The Hempcrete Book the authors describe how hempcrete test panels were left outside, unprotected, for several years without deterioration. My own experience backs this up. At a French Ecocentre, while doing a training course, I saw some hempcrete that had been applied externally as an experiment. A few years later, it was still in good condition.


Hempcrete produces no toxic emissions during the use of the building and does not pollute the indoor environment.

Furthermore, as it regulates humidity and reduces condensation, hempcrete promotes a healthy indoor air quality and restricts the growth of potentially harmful moulds.

Finally, the thermal mass of hempcrete (heat energy stored in the walls) means that building can be well ventilated without cooling down to any great degree. This again contributes to a good indoor air quality.

Environmental and societal advantages of hempcrete


The use of hempcrete, rather than concrete, is preferable in terms of environmental sustainability. To quote Jon Broome from the Green Self Build Book:

”An extremely low amount of energy is required to produce the hemp material, and the emissions of CO2 from the manufacture and curing of lime are very much less than Portland cement, which is now one of the principle sources of greenhouse gases in the earth’s atmosphere.”

The authors of The Hempcrete Book go further and point out that hempcrete is a natural material that is actually “Carbon Negative”. This means using hempcrete in construction will lock up more CO2 in the building than is emitted during the hempcrete’s production, transportation and disposal.

Contribution to rural economy

Greater use of hempcrete in the construction industry would require more hemp to be grown. Although I am not an expert on agriculture or rural economics, from what I have read and watched, this looks like a positive development. The video below goes into more detail on wider benefits of planting hemp on a larger scale for various uses.

Better health of individuals and benefits to society

There is no doubt in my mind that a house made with hempcrete, using natural finishes, is healthier and more pleasant than a conventional new build using highly processed, synthetic materials.

It stands to reason that living in a hempcrete house would have a beneficial effect on physical and mental health. If hempcrete were more widely used in construction, it would mean less pressure on health services and a positive effect on people’s wellbeing.

If this sounds too much like a hippy dream, consider the negative effect of poor housing. It’s well known that damp and mould in houses can be very bad for the respiratory systems of their occupants. Now imagine all of these people lived in hempcrete buildings with no mould and excellent air quality – I’m sure their health and happiness would be much improved!

Disadvantages of Hempcrete


Does a hempcrete building cost more than a conventional building?

Referring back to the Suffolk Housing Society test build, they estimated that the additional cost of their hempcrete buildings was 10% more than the equivalent brick built houses. This was attributed to the increased labour, cost of the materials and the learning process of the contractor. Even so, 10% premium doesn’t seem like much to pay when you consider the thermal performance and comfort obtained.

In The Hempcrete Book, the authors suggest that the construction cost of a hempcrete building should be “broadly similar” to that of a conventional construction. They also make the point about comparing like with like. I.e. the hempcrete building must be compared with a conventional building with high-spec insulation. They also say that there are non-monetary benefits of hempcrete that may be important to the owners e.g. a healthy indoor environment and a low carbon emission construction.

When designing my own timber framed tiny house, I considered other environmentally friendly insulation materials such as wood fibre batts (which I had used before). They are good (but not particularly cheap) and they are not ‘monolithic’ in the same way that hempcrete is. In other words they have to be used as part of a wall system with extra layers (plasterboard, vapour barrier), which adds to the cost and complexity. Hence the reason why I chose hempcrete – it was simpler and no more costly.

To conclude, it’s by no means certain that a hempcrete build will be more expensive than the equivalent conventional construction, especially when you include the long term benefits of living there. As with any big project, you would need to seek quotes from various contractors and be sure that they are comparable.


Hemp shiv and lime binders are not common building materials. You could probably drive into any builder’s merchants and be able to buy foam, glass fibre or mineral wool insulation off the shelf. They almost certainly wont have any hemp in their warehouse.

However, even here in the UK, a quick google search turned up several suppliers of hemp shiv suitable for use in hempcrete. In France, I was able to order both the hemp and lime quite easily from my local builders merchant. So, in Europe at least, the materials are available but you will need to plan ahead and order them from specialists.


As a ‘novel‘ construction technique, it’s safe to say that there are relatively few contractors who have the skills and knowledge required to build with hempcrete (that’s not to say that they could not acquire them for a particular project).

I guess that, for a hempcrete building, the options are:

  • Find a hempcrete specialist
  • Persuade a ‘normal’ building company to do the job (perhaps via a trusted architect)
  • Build it yourself (or at least the hempcrete part).

Drying time

Cast hempcrete walls must be allowed to dry sufficiently before a finish, such as lime plaster can be applied. This takes at least 6-8 weeks, possibly longer if the weather is cold and wet.

Obviously this factor will have to be incorporated into the building schedule.

Clearly, using hempcrete is much less convenient in this respect than using lightweight insulation and plasterboard (drywall).


The main drawback of hempcrete with regard to safety is the alkaline and irritant nature of the hemp binder (lime). Care should be taken to avoid inhaling the dust and getting it onto the skin and into the eyes. The mixed hempcrete is also an irritant and gloves should be worn when working with it. So, as common sense would suggest, make sure to use the correct protective equipment (goggles, gloves, masks) and have eye wash or clean water to hand.

22 thoughts on “Advantages and disadvantages of hempcrete”

  1. Dear Gary,

    My name is Kaisa and I am a university student from Windesheim Honours College. I and my team are currently doing research about sustainable insulation materials and we are especially interested in hempcrete as a material due to its sustainability aspect.

    It was very interesting to read the article about the pros and cons of using hempcrete as an insulation material. Especially the parts where you talk about the unfamiliarity of the material. It would be very interesting and valuable for our research to understand a bit more about the current market situation and general trends in the hempcrete sector. I recognize that you are very busy but would you be up to answer some of our questions in regards to hempcrete and its usage for our research?

    Kind regards and looking forward to hearing from you,

    • Hi Kaisa!

      I have been working with this material and have been pioneering a way to shift the true meaning of sustainable building. Not sure if you are still working on said research, but i would to have a chat with you if you are!

      Marco Salinas

      • Aloha Marco, I’d love to have a conversation with you about Hempcrete if you’re still interested in that! Cheers, Phil

  2. Dear Gary,

    Sorry for the late response. Would you still be up to answer some of our questions? Would it be possible to organize a short online call for that? Thank you for your time!


    • Hello Kansa, yes, no problem.

      I’m a bit busy for the next week or so. Can we make the call sometime after the 8 June? I’ll send you an email then.

      Best regards


    • I’ve no idea why hanging pictures on hempcrete walls could be problematic.

      I have found hempcrete to be an excellent material to get a fixing in. It’s easy to drill into and – when using a good quality plastic ‘rawlplug’ you can easily hang shelves. To be fair, I haven’t tried hammering in the small pins that you often find on picture hanging brackets. But I suspect it would be fine.

  3. Greetings Gary from Australia,

    I have enough land to grow the hemp that is needed. Is there any online manual or books that describe the process how to make hempcrete ? Do you think growing your own hemp would lead to a significant cost saving or are the costs are in reality elsewhere . Big problem with bushfires in Australia, so hempcrete in rural areas makes a lot of sense. Cambridge University research says hemp can absorbs 6 to 8 times more carbon than tress, as it is grows. Sort of a no brainer really !

    • Hello Warren,

      The best book I have is “The Hempcrete Book” by William Stanwix and Alex Sparrow. I would say it should be required reading for a self-builders. This book describes the mixing and use of hempcrete to build with but only briefly touches on the processing of the hemp plant to make it into a building product.

      As for whether you could save significant money by growing your own, I guess that would depend on many factors not least of which is the cost of obtaining ready prepared hemp in your area. I don’t know anything about obtaining the correct type of hemp seeds, whether you need a licence or how to grow it. You would then need to process the hemp shiv into dust-free pieces that have been graded to the required size. This, I imagine, would need some specialist machines. In my case the house was small and the cost of the hemp was less than half the cost of the lime. Maybe with a large building project, some home grown hemp could be worthwhile. You’d need to calculate the volumes involved and all the costs. But I’m a bit doubtful. Another possibility is building with earth and straw (terre paille in French). This is quite similar to hempcrete in that you fill shuttering with a mix of straw and earth. I think it would be cheaper and more eco-friendly than hempcrete but probably not so convenient and a bit more experimental. Maybe worth thinking about if it’s easier to grow straw and dig some earth from your land.

      As for fire resistance, yep, hempcrete is pretty good.

      Good luck with your project!

  4. Hi Gary,
    I just came across your website. I’m part of a group (Wellspring) that is starting to bring hempcrete housing to the masses. Wellspring is set up by 3 Engineers looking to build with low embodied carbon materials and we’ve settle on hempcrete due to the many reasons you’ve gone through. We’ve complete one house on a commercial basis and are doing 8 more on another site. But my question is in relation to the French hempcrete community. They seem to be ahead of the UK by about 20 years in relation to using hempcrete, and we’re thinking of travelling across to France and meeting with them to share experiences and learn from them as we’re interested in the possibilities of using hempcrete as a cladding material on multi-storey buildings. I’ve seen that it’s been done in France and I’m interested to know if you have any contacts there?

    • Hello Pierre,

      I don’t have many contacts in France. I did some hempcrete training at the Ecocentre in St-Pierre-de-Frugie ( and I would certainly suggest contacting them. They still seem to be active with regard to accompanying new build projects and they still offer hempcrete training. It’s a great place to visit too. So that would be my first step.

      Also, you could look at the magazine “La Maison ecologique” ( It’s been going for years. As well as lots of articles on eco-building, it also has a directory with suppliers and artisans working in this field. I would suggest buying a few recent copies and buying some older issues with hempcrete articles. I think you can order copies from their website (under the heading “boutique”).

      Good luck! Gary

  5. Thank you so much for taking the time to make such a clear website – I’m thinking of building something similar in Scotland and this is the best info I’ve found so far. Thank you!

    • Hello Donald, thanks for taking the trouble to leave some positive feedback. I’m glad I was able to be of help. I’ve neglected the blog for a long time but I ought to add some more posts to update it a bit.

      Good luck with your own build and I would suggest getting a copy of the Hempcrete Book, it’s written by UK hemp builders, so I think it’s relevant and it’s fairly up to date.


  6. Gary,
    I’m looking at building partially underground greenhouses for the purpose of harnessing the benefits of geothermal energy in extending my growing season. the idea is that one would build the greenhouse into the side of a south facing hill and use the heat buildup from the sun shining through the greenhouse wall onto and absorbed by the earthen berm wall to maintain a more consistent temperature environment within the greenhouse and most designs include unfinished berm walls but I have a hard time seeing how this would hold up long term so I’m looking for the best method for sustainability finishing them without compromising their purpose.

    • Hello Christina,

      So you think the earthen wall would degrade over time? For what reason? I’m not an expert on this kind of construction, so I’m not sure why the wall wouldn’t hold up.

      I guess you could experiment by putting some kind of lime/hemp plaster over the earth walls, with the aim of making them more resistant. If the walls are damp then I’m not so sure that the plaster will last very long though.

      I did a short course in building with earth, including compressed earth blocks and using earth based plasters and I think it’s pretty tough stuff once it’s dry.

      Sorry I can’t be of more help!


  7. I am planning to build a small eco-learning space in Ontario Canada. ( 15 by 25’). There appears to be hempcrete suppliers and even hempcrete lego block manufacturers in Ontario. My question is, given our zone 4 temperatures to -25 would it be best to build with wood frame and insulate with hemp wool, or build with hempcrete and insulate with hemp wool? I want a 15’ cathedral ceiling and will be using scissor wood trusses for that… it’ll be like a small sanctuary space for TLC, Transformative Learning Community, a 20yrs young international network of ecological educators, indigenous scientists and community facilitators.

    • Hello Eimear, thanks for your comment and for reading the blog.

      It doesn’t often get to -25 in SW France, so building for extreme temperatures is not something I have looked into. How warm does your place get in the summer?

      In your case, there are a few factors to consider. If you are building with hempcrete, you normally still need a load bearing wooden frame (even if this is buried within the cast hempcrete). You wouldn’t normally add extra hemp wool insulation. I guess, due to the extreme winter temperatures, you could add a layer of hemp wool to the building. This could reduce the thickness of hempcrete needed. The disadvantage is the extra complexity (frame to hold the hemp wool, then some kind of facing). If you added the hemp wool to the outside of the building you could retain the benefits of the hempcrete’s thermal inertia.

      If I were you I would do some calculations to see how thick the hempcrete would have to be to cope with the -25 winters. Then I’d calculate the materials cost. If the cost is OK, and you have access to enough free (or cheap) labour to be able to do the build, then maybe just hempcrete would be OK. A thick hempcrete wall would be nice and cool in the summer too. Use of pre-cast hempcrete blocks would increase the cost but could make the build quicker. If I were to build again I would certainly consider them.

      You could also contact the hempcrete suppliers to see what they think. Maybe they could direct you to customers who have built hempcrete houses in your area that you could visit. Another idea would be to do some research to see what other hempcrete builders who live in cold locations (e.g mountainous areas) have done. If you can read and/or speak French then La Maison Ecologique is a French Eco-Building magazine that could be a good resource. They might have some case studies within their back issues. Failing that they have directories of companies in the industry who could probably give you some advice.

      Good luck with your project!

  8. Would hempcrete be good material for a garage? We are looking for a sustainable and appropriate material on a property with a old limestone house.

    • Yes, I think it would be an excellent material. You will have a degree of thermal insulation. Also, hempcrete’s ability to regulate humidity might be a big advantage in terms of reducing corrosion to vehicles and tools. Certainly, in my tiny house, it never feels damp inside – despite me being absent for long periods. Hempcrete is obviously quite labour intensive though. You might want to look into the precast hempcrete blocks that are available?

  9. hello Gary,
    In my study on sustainable construction materials as a university student, I want to know if hempcrete can be used for anything other than only ground-floor structures. Can I use steel for wood as a frame material instead?


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