Two design studios: How we build with wood with a lighter carbon footprint
The use of wood in construction is now a serious component of Danish building stock. For example, BJERG Arkitektur is behind the Fjordudsigten residences in Ringkøbing, which are built of wood. Fjordudsigten has Denmark’s lowest carbon footprint of all completed projects included in a BUILD publication from June 2023. Over a 50-year period, the footprint is 3.1 kg CO2 /m 2/year.
Tegnestuen Arken is the architectural studio behind Kløverbakken in Odder, which was named 'Sustainable Wooden Building of the Year' in 2023. Read about the architectural firms’ experiences using wood in architecture.
We are seeing more timber structures springing up all over Denmark, and it is happening in virtually all types of construction. With good reason, according to BJERG Arkitektur, which is one of the frontrunners in energy-efficient architecture with a low carbon footprint. With around 30 employees, the architectural firm has over 20 years of experience, and around 70–80 per cent of projects on the drawing board are timber constructions.
"In general, our approach to new projects is that if customers don't show an interest in timber construction themselves, we try to guide them towards that path. There are still some prejudices that linger, for example, about the reduced durability of building with wood. But given the many benefits, especially in terms of a lower carbon footprint, we always try to steer projects in that direction."
So says architect Mark Krebs MAA, certified passive house designer, certified consultant in sustainable construction and partner at BJERG Arkitektur.
One of the firm’s newer projects is Fjordudsigten in Ringkøbing, which has just been highlighted as a best practice example in a publication from the BUILD Institute at Aalborg University, as Fjordudsigten has a negative carbon footprint in the operational phase.
Over a period of 50 years, the project will have a total footprint – including building materials and technical installations – of 3.1 kg CO2 /m 2/year. The limit value in the Building Regulations per year is 12 kg CO2 /m 2/year.
Fjordudsigten, Social housing in Ringkøbing
Residents wanted to take responsibility
There is also a prominent wooden housing complex on the opposite coast of Jutland: The Kløverbakken co-housing community in Odder, which in 2023 was named Sustainable Wood Construction of the Year by the Danish association Træ i Byggeriet. Since its founding in 2018, Tegnestuen Arken has had this and several other wooden buildings in its portfolio. Common to all its projects is the use of healthy materials with a low carbon footprint and architecture that encourages social interaction and community.
Tegnestuen Arken has around 20 employees, one of whom is Mette Lind. She was one of the architects who work on Kløverbakken in Odder.
"The client typically has the biggest voice in a project, and the idea of timber construction is something we always introduce to the conversation. In the case of Kløverbakken, future residents were extremely eager to build in wood to reduce its climate footprint and thereby take responsibility for carbon emissions," says Mette Lind.
The Kløverbakken co-housing community was the first residential project to achieve DGNB platinum certification.
Co-housing community Kløverbakken in Odder
Building light and small
There are several advantages to choosing wood as a primary or partial building material, according to both BJERG and Tegnestuen Arken. And this applies throughout the entire life cycle of the material. First and foremost, wood is a renewable resource that absorbs CO2 from the atmosphere as it grows in forests. This storage continues when the wood is used in construction, and it is only when the wood is burned at the end of its lifespan that the stored carbon returns to the atmosphere.
According to figures from 'Træ i Byggeriet', Europe’s total stock of wood products stores around 220 million tonnes of CO2.
“A clear strength of timber construction is that it fits well into a life cycle analysis,” says Mark Krebs.
He points out that the choice of wood has become more transparent and comparable with both wood certifications (FSC® and PEFC™) as well as tools such as LCA calculations and voluntary building certifications such as DGNB.
In addition to carbon storage, wood really stands out for its low energy consumption when producing the structures.
"A clear strength is the thin outer wall construction that you can build with wood. If you build with bricks, for example, you get a heavier building, a larger carbon footprint and a larger built-up area. That’s why we want to move into the field of light construction that wood represents. You can quickly build the outer walls as a modular structure, for example, and you don't have to stand in the wind and rain on the building site, but can produce the finished protect in a workshop," says Mark Krebs from BJERG Arkitektur.
Mette Lind from Tegnestuen Arken explains that, in the case of Kløverbakken, the aim was not only to build lightly in wood, but also to challenge conventional ideas about how much space a typical family needs.
"We have focused on reducing the carbon footprint of our homes, and one of the other approaches we have taken is to design all homes smaller than classic detached houses. Because you can live in less space as a family if the floor plan is optimised, which significantly reduces material consumption. The largest residence in Kløverbakken is 125 square metres and is intended for a family of five people.
Benefits and aesthetics carry the most weight
Both architects believe that timber constructions are by far the most advantageous. However, you need to be aware of how the structure is built and what types of wood are used.
"Of course, you must be careful to choose the right structures for timber construction, for example, by ensuring that water and moisture do not penetrate the structure. That’s always a must. But in timber construction, it gets more attention from the start," says Mark Krebs.
"We sometimes hear that structures built of wood involve a lot of maintenance. This can also be the case if the wood isn't chosen carefully. For example, in Kløverbakken we used heat-treated wood, which means that there is no maintenance other than an occasional washing. Over time, the wood will turn grey and patinate naturally, but it is strong and resistant. Heat treatment is chemical-free, which is one of the reasons why the project is Nordic Swan Ecolabelled," says Mette Lind.
Both architects also agree on the aesthetic benefits that come with wooden buildings.
"Wood is a beautiful and natural material to use in architecture. It creates a special vibe and patinates beautifully," says Mette Lind from Tegnestuen Arken.
"Of course, it’s very subjective, but at BJERG we think timber constructions is beautiful. It's more honest – also on the inside, where, for example, CLT (cross-laminated timber) walls and glulam columns provide a natural look. Wood is a lovely material that smells good and is breathable, which also contributes to a healthier indoor climate," says Mark Krebs from BJERG Arkitektur.
FACTS AND FIGURES: Fjordudsigten in Ringkøbing K
The project in Ringkøbing consists of a total of 80 council housing units designed according to the passive house plus standard. This is also why Fjordudsigten has been highlighted as a best in class example in the publication BUILD from Aalborg University, where wood is a component of several of the highlighted projects.
Fjordudsigten is a prime example of a lightweight wooden building that has a negative carbon footprint, as the homes produce more energy than they use. They are well insulated to retain heat from the sun and have a small ventilation system and solar panels on the roof.
Fjordudsigten, owned by Ringkøbing-Skjern Housing Association, is located in the new 'Nature District Ringkøbing K'.
These homes have the lowest carbon footprint of all completed homes in the BUILD publication. The footprint is as low as 3.1 kg CO2 /m 2/year, which is far below the limit value in the Building Regulations of 12 kg CO2 /m 2/year.
FACTS AND FIGURES: Kløverbakken in Odder
Kløverbakken in Odder is a co-housing community consisting of 58 homes divided into six different types, and a community facility covering just under 7,000 square metres. Tegnestuen Arken designed the co-housing community based on the concept of a village with a focus on social community.
In the process, Tegnestuen Arken worked with input from the residents who now live in the homes, and listened to their dreams and hopes with regard to the creation of Kløverbakken.
The homes are constructed in FSC-certified wood and feature wooden facades, sedum roofs and wild plants to visually highlight the area’s identity as a place that cares about the environment and biodiversity.
The building is both DGNB platinum certified and Nordic Swan Ecolabelled.