Artikel door Christiaan Stuiveling
Mooi! Is the permanent rubric that is published once for every theme. Each time, a different member from the editorial team writes about a landscape architecture or planning project that fascinates them. This edition Christiaan doesn’t exactly write about a project, but rather a development in the construction sector that will affect planners and landscape architects very much in their future careers. This Mooi!explores the beauty of construction with wood: a new, yet centuries-old, material that can fix the housing crisis, while saving the climate.
This period TOPOS writes in the theme of ‘pressure’. Nowadays, thousands of topics could be considered ‘under pressure’ in the Netherlands, like biodiversity and water quality. However, an issue that stand out too me is housing. I know many students which have problems finding a proper place. Nationally, only 44% of the Dutch students lives on its own, while in 2015 this was 53%. The rising costs and short supply of houses are the most important factors for this trend (Kences, 2023). Other age groups which also demand smaller apartments, such as starters and seniors, face the same issue. And this amount of smaller households increases rapidly. Today, the average Dutch household consists of 2,1 people. In 1963 this was 3,5 (CBS, n.d.).
A possible response to the housing shortage is splitting up large houses into smaller units. Another approach is to simply built more (smaller) houses. However, building seems more difficult than ever, because of the nitrogen-emissions that come along with construction. Furthermore, construction produces a set of greenhouse gasses which drive climate-heating. If we want to continue building, something has to change.
Luckly, a promising new construction technique has recently gained traction. You may be surprised that its main component is wood, a material that people have used since time immemorial. Historic wooden buildings proof the enormous potential durability of the material. In Best, Noord-Brabant, a farmstead from 1263 still stands, completely supported by a timber frame. The same hold true for café ‘In t’ Aepjen’ in Amsterdam, which has a timber structure dating back to the 16th century. Even so, during the last two centuries, wood was gradually replaced by concrete and steel. The primary driving force behind this shift was the pervasive concern over fire hazards.
Figure 1: Farmstead 'De Armenhoef' was built in 1263 (Wasmus, 2012)
CLT The resurgence of wood has been made possible by a new technique of processing of the material. Rather than providing wood in the form of beams or tree stumps, modern architecture uses cross-glued timber plates. This material is called cross laminated timber (CLT) and it is stronger and less flammable than unprocessed wood, especially when treated with flame retardant. CLT is perfectly safe for low-rise housing. High-rise is perfectly feasible in combination with some concrete to provide weight and stability. An example of such a hybrid is a tower called ‘Mjøstårnet’ in Norway. The tower is mainly built by wooden materials (even the lift shafts!) and it has a total height of 85 metre (Abrahamsen, 2017).
Figure 2: Cross laminated timber is made by guiling wooden panels perpendicular to each other (Stora Enso, 2021)
Wood has some qualities which make it future-proof:
First of all, building with CLT leads to less nitrogen deposits. The construction sector is responsible for only 0,6% of the total nitrogen deposits (NH Nieuws, 2022) in the Netherlands. Nevertheless, several projects have been cancelled because of their nitrogen emission. It is therefore important to take nitrogen-emission into account. CLT is pre-fabricated in the factory. Some nitrogen is emitted by transporting CLT to the construction site, however this is limited due to the low weight of wood. On site, the specific building elements only have to be screwed together. Less heavy machinery and lifting movements are required on the construction site. Therefore, nitrogen emissions are lower.
Secondly, CLT is C02-friendly. The emissions from the manufacturing of materials used in construction of buildings account for 8-10% of the global Co2 pollution (UNEP, 2022). This is mostly due to the carbon-intensive production of steel and concrete. Wood provides an alternative. In comparison, when producing a slab of CLT, only 25% of the C02 emissions of an concrete slab are emitted (Jae-Won Oh et. al, 2023). Moreover, trees capture carbon during their growing stage, which gets stored in wood. The amount of carbon that it sequested in CLT is about 4 times greater than the amount that is emitted during production (Jae-Won Oh et. al, 2023). Building with wood can thus acts as a ‘carbon sink’. When building with CLT, a city can become a massive carbon storage. I argue that it is better to invest 2 billion euros in storing carbon in sustainable housing with CLT, then to invest this in the development of carbon storage under the Noorzee, like it is done now (NOS, 2021).
What hinders a ‘wooden revolution’?
Despite these favourable characteristics, CLT-construction accounts for only 2% of new construction in the Netherlands. How is that possible? It has to do with multiple factors, such as: old building codes, unfamiliarity with the material and lack of schooling around wooden construction. However, in the Netherlands the biggest obstructor of wooden construction is the ‘Milieu Prestatie Gebouwen’ (MPG). It is an assessment which determines the environmental impact of buildings and mandatory for any construction permit. Currently, wood is poorly rated, because the temporary storage of carbon is not measured in the MPG. It is assumed that wood has short lifecycle and that it gets after incinerated after 50 years. This is not true. Wood doesn’t deteriorate that easily when kept dry. Moreover, a wooden building is easily dismantled and the wood in it can be used for other high-end purposes for tens of years. To unleash a ‘wooden revolution’, the MPG should be favourable for wood (and other biobased materials). Despite a manifest published in 2020 (Vorm, 2020), signed by a range of architectural and construction firms, banks and other stakeholders, it is only until 2024 that Dutch government may change legislation on the MPG (Het Houtblad, 2022).
An exciting ambition of the AMA
Fortunately, there are institutions that remain determined to utilise the advantages of wood for society. The Amsterdam Metropolitan Area (AMA), consisting of 30 municipalities in Noord-Holand and Flevoland, have set the ambition to build 20% of their new housing with wood in 2025 (Metropoolregioamsterdam, 2021). It is a very ambitious objective as currently only 2% is built with wood. However, when the plan succeeds it cuts nitrogen emissions and reduces a yearly 220.000 ton CO2 emission. Besides, the houses look wonderful! (see figure 3).
Figure 3: Ex- and interior of 'the Warren', an example of a wooden building in Amsterdam (Pieters Bouwtechniek, n.d.)
In 2025 starts the construction of the Mandelabuurt. The project will historical, as it is will be the first wooden neighbourhood in the Netherlands since a long time. The complex is planned on the edge of the Mandelapark, in the southeast of Amsterdam. The Mandelabuurt is going to provide 725 homes for approximately 2100 residents. Moreover, a primary school is ging to be built, all in wood. The sketches of the neighbourhood look great and the wood fits beautifully in the park-context.
Hopefully, the Mandelabuurt will truly mark the beginning of a Wooden Revolution so that one day I can live in my own timber house!
Figure 4: Artist's impression Mandelabuurt (Gemeente Amsterdam, 2022)
Figure 5: Visual of Mandelabuurt from human perspective (Gemeente Amsterdam, 2023)
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