The technology of using CLT wood in construction is growing into more myths as its popularity increases. An example is the office building designed by the AMBIENT studio, which has stirred up quite a discussion. We ask Magdalena Pios (AMBIENT) about the building itself and the popularity of CLT.
Wiktor Bochenek: The building designed by AMBIENT will be the first building with a building permit for an office building in wood technology. Was it difficult to obtain this permit?
Magdalena Pios: I would say that obtaining the permit itself went quite smoothly, but the difficulty of this project was to develop such spatial, structural and material solutions that would ensure compliance with building regulations and meet the utility requirements for buildings with an office function.
Here I would like to clarify - the building we designed is the first mid-rise office building with wooden technology. Other office building projects have appeared before, but they did not exceed 12 meters, so they fell into the category of low-rise buildings. In contrast, our building, with 4 floors and 16 meters in height, was already in fire resistance class B, where the required fire resistance of the main structure is R120, that is, the main structure of the building must withstand a fire lasting two hours. This was the first challenge we had to face.
The next issue was the nonproliferation of fire. According to the requirements of the technical conditions, the structure, exterior and interior walls of the building must be non-fire-spreading, which is easy to achieve with standard technologies, but more complex with wooden elements. In addition, there are issues of installation distribution, acoustic issues and thermal and moisture issues. Since the building is designed with prefabricated elements, it was also necessary to develop the principle of division into prefabricated elements. In order to obtain the agreement of the fire expert, already at the stage of the construction project we had to submit for an opinion specific proposals for the connection of building elements, methods of securing them to the NRO class, but also installation solutions. At the same time, some of the solutions go beyond the standard systems available on the Polish market. In this respect, it was definitely a more labor-intensive and extensive project than a typical project at the construction stage.
Wiktor: The uptake of CLT technology in the Polish market is primarily for single-family houses - is this changing? What barriers are standing in this way?
Magdalena: In addition to single-family houses, a few public buildings have already been completed in Poland, such as kindergartens or office and training buildings of the State Forests. These are small-scale buildings for now, but gradually the technology is being tamed by both investors and architects, and the scale of application of this material will certainly grow. Of course, there are requirements in the Polish regulations that contribute to limiting the scale of buildings or increasing the cost of implementation. An example that raises costs is, for example, the need to protect the surface of CLT panels to NRO class. In most other European countries there is no such requirement. However, the process of changing the regulations has already begun, and it is hoped that the legislature will also come out to meet the growing interest in wood-based technologies.
Here it is worth noting that wood technology is a very wide and growing set of solutions that have different properties and can be applied differently. We, both in the design of the office building and in the design of the recently completed library in Choszczówka, used a combination of different wood-based technologies, selecting the technology according to the needs and requirements for specific elements. In the office building, CLT panels are used as floor slabs, but other elements are made of glued laminated timber (GL) or as framing panels. The right choice of solutions ensures optimization in technical terms, but also in terms of the cost of implementing such a building.
Wiktor: Isn't access to materials on the Polish market also an obstacle in this process?
Magdalena: At this stage, indeed a large part of the structural timber comes from other European countries - Austria, Germany, Scandinavian countries. If we would like to adopt the principle of building large-scale facilities with materials produced in Poland, their availability and price may be a limitation. When planning a large-scale investment, you have to reckon with the fact that some elements will be supplied from outside Poland. When designing our building, however, we confirmed that a Polish manufacturer is able to provide glulam for the columns and beams that make up the main structure of the building, while the CLT slab floors must be imported. However, the distances in Europe are small enough to consider that European wood is still a locally produced material. It is important that the wood used comes from documented sources, certified by the FSC or PEFC to show that the manufacturer has practiced sustainable forest management.
Of course, if we are calculating the carbon footprint of a building, we must also add the footprint resulting from transportation, but overall the use of wood instead of reinforced concrete or steel will contribute to reducing emissions. So there are limitations when it comes to the origin of the wood, but nevertheless Poland is the third exporter of prefabricated wooden houses in Europe. These buildings are mainly produced in timber-frame construction, but a production line of CLT buildings is also currently being launched in one of the large factories. Polish companies export prefabricated single-family houses, multi-family houses and now public buildings to Germany or Norway. These buildings could also be realized on the Polish market.
The building designed by the studios is the first mid-rise office building using wooden technology
© AMBIENT
Wiktor: Why is it worth paying attention to wood technologies in large-scale construction? Is there a chance that wood will displace concrete?
Magdalena: The construction sector accounts for about 40% of global CO₂ emissions. The production of concrete and steel, which are basic construction materials due to their very high energy requirements, is associated with high emissions. Steel is a reusable material, so in some time, if the share of renewable energy in steel production increases, it too will be a green choice. Concrete, on the other hand, is a difficult material to reuse. The first recycled aggregates are emerging that can be used to make new concrete elements, but it is still a niche solution. In addition, a scarce resource - sand - is being used to produce concrete. With the principles of a closed-loop economy being implemented in the European Union and climate policy in general aiming to reach climate neutrality, i.e. zero net emissions by 2050, natural, renewable, low-carbon materials, which include wood, have become the focus of the construction industry again. With the goal of realizing zero-emission buildings, we must look for solutions to reduce the embedded carbon footprint.
In many cases, wood, wood-based products or other natural products can replace more carbon-intensive materials, and this does not only apply to structures, but also to thermal insulation, finishing materials or facades.
Wiktor: The Poleczki Park office building project has succeeded primarily in reducing its carbon footprint. What are the advantages of using CLT, and what are the disadvantages of this technology?
Magdalena: First of all, CLT is slabs, so it's a technology that can be used in an office building for ceilings and exterior walls. Because of the need to maintain an open flexible office space, the main structure of the office building is the so-called "heavy skeleton", that is, it is columns and beams. CLT technology is more at home in buildings with wall structures. Such buildings are, for example, multi-family and hotel buildings.
CLT technology, like all prefabricated technologies, can provide a higher quality of workmanship than that obtained when the entire project is carried out on site, shortening construction time and reducing its inconvenience. Due to better planning of the use of materials, waste generation is reduced. Here it is important that the project is created from the beginning on the basis of specific technical solutions. Then it is possible to adapt the solutions to the available dimensions of the elements or transportation possibilities. Knowledge of the technology and the designer's understanding of it translated into design decisions from the concept stage can provide effective solutions that reduce both the facility's carbon footprint and its costs. Otherwise, cost may prove to be an argument against the use of wood.
By using CLT and glulam, we can create interiors in a building that will benefit the well-being of the occupants, which has already been confirmed by numerous studies. For example, a study conducted by the University of British Columbia found that people in rooms with furnishings made of wood had lower stress levels, lower blood pressure, and better concentration than those in a room without natural materials during the study. In hospitals, wood contributes to less pain and faster recovery for patients.
Wiktor: Do you see a future for wood technologies in Polish architecture?
Magdalena: A survey of Poles' attitudes toward wooden construction conducted by the Ministry of Environment in 2017 showed that more than 35% of respondents had not heard of year-round wooden houses, and less than 1% of respondents associated wood with public buildings. In 2021, wooden buildings accounted for just 1.1% of residential buildings put into use in Poland, while in countries such as Sweden, Austria and Germany, prefabricated wooden construction accounts for about a quarter of the housing market. Poles are very conservative, but certainly awareness of wooden alternatives to standard technologies has increased significantly since 2017. What is needed is a few first implementations, on which design standards and methods of assessing the work by inspectors will be developed, and then the dissemination of these competencies.
Knowing that according to the European Green Deal, EU countries are to reduce CO₂ emissions by 55% (compared to 1990) by 2030, and Europe is to be climate-neutral by 2050, we know that construction requires a fundamental transformation. This transformation is expected to reduce emissions in both the operational phase of the building and the embedded carbon footprint. Already implemented and upcoming regulations, will require low-carbon solutions, which will certainly increase the use of natural materials. According to the currently proposed amendments to the Energy Performance of Buildings Directive (EPBD), providing the carbon footprint value will become a mandatory part of energy performance. Other legislation that will accelerate the reduction of the carbon footprint associated with investments in the construction sector is the CSRD, which obliges companies to report the environmental impact of the company's activities, and the Taxonomy, which defines ways to assess which investments are environmentally sustainable.
The regulatory environment will therefore force the search for solutions that lower the carbon footprint, and therefore use low-carbon materials for construction. Such investments will also more easily obtain financing. It can therefore be expected that wood construction - despite the reserve with which we approach it in Poland - will become increasingly common in our country.
Wiktor: Thank you for the interview.
