‘The opportunity for hemp is to integrate with modern technologies and building methods’

Liam Donohoe is a lecturer in Engineering at Technological University Dublin, where he earned a Master’s degree in Energy Management. As a PhD Fiosraigh Scholar at TU Dublin’s School of Electrical and Electronic Engineering, he is researching the development of an international standard rating methodology for the dynamic energy performance of hempcrete. A specialist in building energy certification and no- and low-carbon product, standards and systems development, Donohoe founded Black Mountain Insulation Ltd., a global leader in natural insulation materials. He is a director at the International Hemp Building Association (IHBA) and at UK Hempcrete (UKH) where he is Chief Operations Officer.

HempToday: When it comes to bio-based construction materials, what is hemp competing with?

Liam Donohoe: Hemp is competing with everything else in the market. When we pitched the UK Hempcrete business to investors, we had a slide showing the main biobased competitors in Britain and Ireland. The investor we were talking to said, no, tell me you are competing with Kingspan, you are competing with Knauf, you are competing with Rockwool.

A few months later, Kingspan had made two significant investments in the biobased space. His point was: “You are telling me, hemp has the potential to go mainstream. Walk it and talk it.”

HT: What makes hemp better than rammed earth, straw bale, or other natural building materials?

LD: It’s not a case of hemp being “better.” It’s a case of hemp being at a more advanced level of development. We see biobased materials being complementary to hemp as we share similar visions and ethos. But hemp has been invested in and researched so professionally and thoroughly now, at least in Europe, that we have got it to a point where, like any other fiber insulation or low-carbon, insulating block material, it can be specified and implemented in any construction project, from a garden shed to a large international office. UK Hempcrete has clients at both ends and all points of the spectrum in between. Specifically, we see more commonly that architects representing clients often come to us saying, we want to cast hempcrete, and we say why is that, haven’t you heard about ISOHEMP blocks? These are fully certified, dry, solid, regular, and arrive on the site just in time when you need them.

Rammed earth and straw bale just don’t yet arrive on the site according to the building cycle.

Meet Liam Donohoe at the International Hemp Building Association’s 12th Hemp Building Symposium Oct. 15-16 in Staffanstorp, Sweden

HT: What can hemp construction do for the global challenge in housing needs?

The opportunity for hemp is to integrate now with modern technologies for lean construction, and also with modern methods of construction. So I think we will see more modular housing concepts, for example, something like Ian Pritchett developed with BIOND, and now Greencore, Dun Agro and, of course, ISOHEMP, have done with their blocks which we distribute in the UK. We could spend every day reviewing scalable projects with the number of inquiries we now get from housing developers. Also, in the university, we have been working with timber frame home manufacturers, and hope to develop a project there soon.

HT: The concept of the “passive house” looks like a marriage between traditional construction and technology. What’s your view on this whole movement?

LD: I wrote an undergraduate paper on the hemp passive house. My studies had shown me it was possible. During my visit to the amazing Nauhaus in North Carolina, I saw it leap large up from the earth. In Ireland, James Byrne also designed and built an amazing hemp passive house. UKH are currently designing two houses for clients in Northern Ireland to passive house details and standards. But you know what? It’s not a case of hemp adapting to the passive house concept. It’s about the passive house concept adapting more to hemp-lime! That’s what we are doing now. In the International Hemp Building Association (IHBA), we are working with the European Industrial Hemp Association (EIHA) with the EU Standards group to educate policymakers on standards for hemp blocks.

HT: Talk a bit about energy technology in the home. It would seem that certain “smart” technology applications combined with hempcrete construction could yield maximum performance with respect to both carbon emissions and energy efficiency.

LD: Ha! Yes and no. Let me tell you about one of those houses in Northern Ireland we are designing at present. Among the things I do — and let’s just say, it’s a skill I have that’s a lot more advanced than my guitar picking — I work in Britain and Ireland for retrofit and new house energy coordination and certification with energy performance standards. When I ran the numbers on the Northern Ireland hemp-lime house, it is so highly insulated, the client and I worked out it needs little more than a wood-burning stove with a back boiler to heat the home.

But the regulations don’t allow for that! How crazy is that?  A hemp-lime house is too good! They want us to put in electrical heating because they come with a regulator and/or timer.

So that’s a case of us having to provide for unnecessary technology because hemp construction is too advanced and regulations haven’t caught up with it yet. The client there may also put in some solar photovoltaic panels, but he just wants to build the house first.

Regarding a situation where you decide you need more advanced technology such as heat pumps, for sure they are extremely well integrated with hemp-lime construction. Smart weather compensation on the outside unit of the heat pump will tell the controller when and how to switch on and get indoor temperatures back up to set point. With a material with slow decrement delay like hemp-lime, that means your compressor will have to turn on less often. The result is the running cost of your heat pump will be lower.

In UKH we often subcontract to clients the services of the leading expert for dynamic simulation modeling for hemp lime-constructed houses in Britain. With years of experience and real-site data built into the model, we can provide a predicted lifetime energy and carbon use datasheet to clients that empirically shows that O&M costs will be lower with a hemp-lime building. This is often convincing to clients building a bigger home. As Alex Sparrow likes to say, “Can you afford NOT to build with hempcrete?”

Our partner, Mura Canning came up with a tag: “Biobased solutions that don’t cost the earth.”

HT: Where do you see product development regarding hempcrete and hemp fiber insulation; what’s happening now; where do you see it going?

LD: As said above the main applications are likely to be labor and cost-saving construction models BEFORE the building site. So modular and pre-framed cassettes etc. Chloe Donovan and Mike Lawrence’s amazing natural building system has a lot of promise there.

However there is still much work to be done in several areas. These include the development of ultra-low-carbon binders (which I’ve concentrated on with my own research work, and under the inspiration of the great Steve Allin who has shared his binder recipes to further science).

HT: Talk about application techniques; spraying, infill, bricks, blocks and the relative strengths and weaknesses of each.

LD: I have a lot of time for blocks because I feel they are more adaptable to how the majority of homes are built today. However, spray has great potential as well, not only in modular construction but also in more mass-scale retrofit of old barns and stone houses. We are only scratching the surface of the retrofit wave in Europe at the moment. Infill has a place there too. But rather than talk about weaknesses or strengths, it’s more about what is the best solution for the project, for the client, for their time horizon and for their budget.

If a person has access to labor, and/or skills in construction, infill is just as good as anything else. But the time horizon has to be there to allow for drying etc. and then the finishing trades.

Blocks just allow a lot more flexibility to the build cycle and this is important for many.

HT: Talk about the importance of standardization to the construction industry, and what standards are crucial for hempcrete to meet.

Certification is germane to construction now for many reasons. Let’s just look at one.

Take Grenfell for one example, where there was apparent certification in place but it was bullshit! It wasn’t worth the toilet paper it was written on! Now it might seem like I’m contradicting myself a little there, but, in fact, what I mean is that robust certification has to be in place. Architects and professionals want to specify biobased but they also want to specify with confidence. So hempcrete has to be better than everything else. We already know it is anyway, but we have to have that written down and tested and have it on a sheet somewhere so that when the energy certification or building control guy like me comes around with his clipboard, there it is and I file it.

That is why in UKH we have developed a suite of services that starts with the customer along every stage of the journey. It’s why we emphasize to clients that they can use any type of binder or block they want (and we supply most of them) but that these ones over here are the ones we most strongly recommend. 

That’s because they come with a suite of data, tests, regulations, and standards. More importantly, when the ISOHEMP blocks you ordered from us come on-site, they won’t all be different sizes and irregular. And how do we know this? Because we went out to the state of the art factory in Fernelmont and we saw their quality assurance processes at first hand. 

I could talk more about risk assessment, and mitigation, as well as insurance, but as those topics aren’t very interesting really, I’m going to stop. But that’s just it isn’t it? In hemp construction, we sometimes downplay the value of such things. Look here: I am almost doing it again!

But the rest of the building world takes this stuff deadly seriously and so should we. Hemp just has to go through the rest of that product cycle until it becomes as boring as the rest of the construction industry. That’s when we will know that any doubts or perceptions of incredibility no longer exist. When it’s so standardized that no one even asks about it anymore. When Joni Mitchell brings out an updated version of Big Yellow Taxi and it goes: “They paved paradise, and put up a hempcrete EV parking lot”