Anna Ostrowska talks with architect Aleksander Krajewski about the advantages and modern features of building with the use of straw, wood and hempcrete. This design niche awaits its buzz moment but who will be the one to press the button?
Aleksander Krajewski
I would like to start our conversation at the point where you ended your text published in the ‘Autoportet’ magazine [68/2020]. The topic of that issue was ‘New Hope’. In the last paragraph you wrote: I am starting several building projects in the natural system. We will design with straw, clay, hemp and wood. Not a single drop of rain that falls on the plot will end up in the sewage system. We will not connect the buildings to the gas network (…)’. What is happening with these projects at the moment?
Unfortunately, so far we have not managed to get necessary permits to start the construction.
And why is that?
I try to be honest and straightforward with my clients, which leads to a moment when they ask a lot of questions. They want to know exactly what I am convincing them, especially if they hear for the first time that there is something like a concrete made out of hemps or that you can build modernly using straw and that such a building won’t collapse or won’t burn down. I am talking about all the advantages of these solutions, but it would be unfair to ignore the disadvantages
If that is the case then, what are the difficulties in building with natural materials?
First, there are certain restrictions on the construction site. Also the technology of making such objects requires certain knowledge and experience, which is uncommon to the majority of the construction teams. Those that are usually available know how to build with hollow blocks and cast reinforced concrete, but if someone tells them about a straw house, they will first laugh and, secondly they will make strange eyes and not take the job all together.
Are you trying to say there are no qualified teams that will build such a house from A to Z?
It is not that there are no such constructors at all, there are teams that know what they do, there are also whole groups devoted to natural construction and enthusiasts who build such facilities on their own, using the economic method and willingly sharing their knowledge and experience. There are also many books on natural construction that I successively buy and read. There are examples of successful implementations in Poland and abroad, but in the end it all comes down to performance and potentially a higher price, because when there are few contractors, the deadlines are also more distant and the prices for execution get higher. In this context, we are also not talking about hyper-modern technologies, on the contrary – they are much older than reinforced concrete.
What pro-ecological solutions bring the most enthusiasm to today’s customers?
Certainly, it does not take much effort to convince a person to collect rainwater or to set up a green roof, in general to the solutions that help save energy or improve the luxury of the property. For example, due to the fact that you can create a green roof – it makes an additional recreational space and a place where you have a good time and where you can install, for example, a jacuzzi. Although if someone in Poland can afford to build a house, they can probably afford to waste rainwater, because water is very cheap in our country. Certainly, environmental awareness in Poland is growing and it gives hope, but there are not many houses built in the natural building system and those that are, usually are small, private investments, built with economics in mind. Customers are open to new technologies, such as photovoltaic panels, heat pumps and recuperation. However, I try to look for ‘low-tech’ solutions – which always work, not only when we can afford them.
Do you see an opportunity for introducing natural materials and techniques to construction on a larger scale in the near future?
At the moment, from my perspective, the only way to popularize natural solutions in architecture is to include them in the guidelines or recommendations of the architectural competitions. So far, the most spectacular example of using natural sources in Poland is the Copernicus Science Center, where one part of the building was made using compacted soil. But even this is an example from over 10 years ago, not brought to the attention of the architects, nor repeated in any other public utility building. Fortunately, there are many examples of the implementation of this method around the world.
What are the biggest obstacles around building with clay, straw or hemp?
The biggest barrier is that we do not have enough examples of natural architecture.
And we have so few examples, because the minority of people decide to use these solutions, and the investors lack the trust towards natural materials. There are not enough specialized construction teams – as I mentioned -therefore the prices go up and vicious circle closes.
We started our conversation discussing obstacles and difficulties, so the readers might get the impression that building with natural sources takes just too much effort. Why is it worth overcoming these issues? What are the benefits we get in return? I can think of the qualities such as the fact that we have lower environmental costs, lower carbon footprint, better quality of the living space without inhaling toxic substances. And all that with the usage of less energy. How does a building made of natural materials compare to a block of slabs or a house made of hollow blocks on a reinforced concrete structure?
The answer is both simple and difficult. We would have to build five identical buildings with the same cubic volume, almost equally oriented towards the directions of the world, with the same light exposure to obtain meaningful data that can be measured and compared. It is almost impossible in a practical sense, we can only compare certain coefficients or properties of the materials used for construction and calculate them using mathematical and physical methods. The main problem I see though, is the current methodology for calculating energy performance.
Why is that a problem?
It is a common assumption that buildings should be like a thermos – when we isolate ourselves from the outside environment, the heat will not escape, so the building will be economical. And this is simply not the case, because when calculating the energy performance of a building, something such as the thermal inertia of the material is not taken into account. In the case of reinforced concrete, ceramic blocks or cement blocks, it is almost nonexistent compared to, for example, solid wood, clay consolidated with straw or hemprete.
So in the light of the current methodology natural materials look like of a lesser quality?
The natural materials that I have mentioned have not as good of isolation performance, which is a feature that can be measured and presented in a construction project. As a consequence, these materials are automatically rejected because they do not meet the requirements set out in the law regulations. While in reality these natural materials have the desired property that they heat up for a long time and slowly release the heat afterwards. In the aftermath they help to sustain the temperature in the interior at a constant level despite large temperature fluctuations: daily or monthly. This translates into better air quality and lower energy consumption. Unfortunately, in the general sense of the architectural law, this quality is not taken into account. The traditional calculations do not consider the life cycle of the building and the origin of the materials, and therefore their carbon footprint.
I understand that there are also costs of production of the materials and their transport to the building site.
Yes, the environmental costs are different for, let’s say, clay that lies one meter underground on a plot of land. Theoretically, it would be possible to build a clay house from what is usually needed to be excavated for its traditional substructure. Most of the materials that are needed could be located on the plot of land or in its close proximity, which is unattainable in the case of hollow blocks, reinforced concrete, steel, polystyrene, plaster, etc. The paradox is that on the one hand, natural construction is very accessible, and on the other, we have an executive block which I mentioned earlier.
So in this case, a change would arrive with the change inside of the construction law. So that it becomes more detailed and aware of the range of factors that reflect the amount of energy used at each stage of the construction process, as well as during the lifespan of a given building.
On top of all that, there is the most pragmatic thing. Imagine a construction site for a single-family house or housing estate, which, after the construction is completed, practically needs to be cleaned, call a team that will dig the area and remove all the scraps of blocks, polystyrene, plasters, mortars from the ground and take them to rubble, which to be honest is rare – rather the ground is leveled and covered with a thin layer of earth. Later, you can admire those gardens where nothing wants to grow, even a shovel cannot be stuck in, because the rubble is so shallow. In the case of a house made of clay, straw and wood, all construction waste can be left and it will decompose, additionally fertilizing the soil.
Like a small-scale circular economy.
In fact, there is no need to clean up after such construction. But does anyone keep in mind this small cost of the entire construction cost? Usually no one thinks about it, and it seems to me that it is also of some value. There are probably more advantages of natural construction, but for me the ones I mentioned are the most important. It is also worth adding that the cultivation of hemp absorbs huge amounts of CO2 from the atmosphere, which gives this material a negative carbon footprint. So by building naturally, we could actively reduce the carbon footprint, not only recover from zero, but also minimize it. This is also a parameter that is not included in the construction law.
Maybe the problem with the availability of construction teams can be partially solved by using prefabricated construction elements made of, for example, straw and wood?
Straw can be easily used to prefabricate entire elements: walls, roofs, floors. Prefabrication technologies are available, indeed whole houses arrive on a truck for construction – all you need to do is prepare the foundation properly and the building is finished within a few days. Prefabrication has its limitations because for example the sugar contained in the straw is a food for various types of fungi or insects and if such straw is wet or flooded, it may lose its properties. Half of the year in Poland is quite rainy, which is a certain inconvenience that you have to deal with on the construction site. In the case of prefabrication, the entire building is built in a hall, where the conditions are perfect and you only have to wait for a proper weather window to assemble it on the site within a few days. I also saw another solution in Norway, where a temporary protective structure is being built on the plot – a temporary hall. In this way, the construction site is partially separated from the external environment – the construction season is actually a bit shorter there, but as you can see, these obstacles can be overcome in any case. As a result, houses with cellulose insulation are created and meet the requirements of passive buildings, which is worth emphasizing. Moreover, it is possible to create a facility only from straw, without the use of a wooden structure. From what I know, even in Poland such a building was made, but it is of a minor beauty – its walls are over a meter thick. Straw is the only material there, functioning as an insulating and structural function, with no additional skeleton there. So, even such solutions are possible.
What is the preparation process for a straw or hemp to become a material which can be used for construction? Also: do we have suppliers of natural building materials in Poland and is the certification of natural materials a good way of popularization?
The issue differentiates with each of these materials. Just like no one in the country will be afraid of a log house, because wood is in common use and no one has any doubts about it. As for the straw – people have their doubts but the preparation process is exactly the same as it is during the harvest season. The difference is that you need to set the dicing machine to a slightly higher power in order to obtain a cube with a greater compactness and density. In practice, the farmer selects the power so that the final dice are not too heavy. If they weigh too much they cannot be used for construction. You must also make sure that the straw cubes do not stand directly on the ground and do not get wet. And that is basically it.
How about cannabis and hemps?
Here the situation is a little bit harder. Obtaining concrete out of hemps is a challenge of a greater caliber, because cannabis in Poland is subject to anti-drug law. There are special companies that certify hemp seeds for industrial purposes, which makes obtaining permits and growing these plants inherently more expensive. Another difficulty concerns the cultivation itself. Hemp is a very tall plant, measuring from 3 to 5 meters, and each part of it is used for something else. This means that you must have a special harvester for it. The agricultural machine has to cut the hemp at three heights and separate the top panicles from the stems already in the field. This is how the crops are sorted while mowing. There are just a few such machines out there. I know that the Czechs produce them, we do not have a manufacturer of this type of equipment in Poland. The whole technological process is long and it’s not like you can go to an agricultural equipment wholesaler and buy a few machines, and then start production. I know that there is one company in Poland that deals with this.
Are you talking about Podlasie’s Hemp?
Yes, besides, you can import hemp from Lithuania, the Czech Republic, as far as I know, Germany also grows it, but there is a certain paradox associated with it, it would be good to speak about it out low. In the 1970s and 1980s, Poland was one of the largest hemp producers in Europe, we exported it to a great extent. This is our native plant, so to speak, and it might be used for producing car bodies, furniture, clothes, cosmetics and as a building material. Unfortunately, all of this was lost. It is absurd that Polish law is a barrier to the development of cannabis cultivation and the continuation of our tradition. For the second time in this conversation, we come to the point where Polish law is an obstacle to natural construction becoming more mainstream.
It is a bit sad and frustrating but I am glad that such obstacles can be precisely named and identified. You have mentioned so far a few barriers that must be overcome in order for ecological methods of building to flourish. With natural construction we also have many additional, already embedded advantages which, in my understanding, point to the direction of these solutions quite naturally – so to speak. After all, we are still largely an agricultural country. Straw is a popular material, it is easily available. With the right amount of a political will, these obstacles can be overcome.
Agreed, but – to cool down your enthusiasm – that change would require an amount of lobbying. The question is, who would do the actual work of it? Who could be a beneficent here in terms of business? Unfortunately, still few people know about these solutions, and the greatest promoters of this type of construction are architects, who are few in the construction industry. Architects are a relatively small group in the Construction Chambers compared to, for example, constructors or installers, who certainly do not care about natural solutions, because many of these buildings would not require such expensive and modern technologies, such as maintaining adequate humidity or air conditioning. Insulation coefficients are constantly increasing to condemn us to more sophisticated, modern technology, which – let’s be honest – is also expensive. I am afraid that if the Polish state does not see any interest in promoting natural construction solutions, it will be very difficult to convince the general public that this is a better way. In order to create a large group of people who will lobby for it, it will be an even more difficult task. Of course, there are various business associations, such as Polish Green Building Association, that promote pro-ecological solutions, but let’s be honest, it reaches a handful of industry experts and almost no one else. It is a pity because especially now we are facing one of the greatest opportunities in raising this topic to the attention of a broader public.
What do you mean by that?
There are government’s plans that could be used for it, although they are not entirely consistent with my views. I am talking about the new law around the houses up to 70 m2, which can be created without a permit and the architectural competition for the model projects of such houses. If, within this competition, it was noted that you have to use traditional Polish construction technologies and materials like straw, concrete made of hemp, wood, if it went in this direction, there would be a classical two birds one stone situation. You can then turn a blind eye to the spatial chaos that this legislative proposal will cause in the near future, because at least these buildings would be ecological and sustainable. However, there is little to no chance that such provisions would appear in the guideline for this competition.