You will hardly see it when it's done. All structural floors and walls of four of the five storeys of Bredius are made of CLT. Yet the only thing that will eventually remind residents of it is the beautiful wooden ceilings.

Wrapped up

There is a reason for this, says project planner Martijn Houweling of Ballast Nedam West. ‘Timber construction is beautiful, but it brings some challenges. CLT stands for cross-laminated timber. It’s an extremely strong and stable material. But it is vulnerable to fire, moisture and sound. We address this with secondary wall systems. We use them to cover the walls as soon as they are installed. To expose the wood to the elements for as short a time as possible, we build vertically. We always build a small section all the way up, followed by the next section beside it. In this way, the CLT is immediately covered and protected. But just to be on the safe side, we also install mobile smoke detectors during construction.’

Winter and waterproof construction

Arjen Arens, Head of Planning & Development at Ballast Nedam West, explains how the moisture is kept out. ‘The floors, which consist of thick layers of CLT, gravel, rock wool and a screed, are wrapped with 'Wet Guard' membrane. We can easily wipe the rain off that. Before proceeding, we use moisture meters to determine if it has dried sufficiently. So we build winter- and watertight, and only then start the finishing work.’

I like to work on projects that leave the planet in good shape.

Arjen Arens Head of Planning & Development Ballast Nedam West

Asking questions and optimising

It is clear: timber construction is quite different from building with only traditional materials such as concrete and steel. What does that require of all those involved? Arjen: ‘You have to think carefully about everything. Constantly asking questions based on our construction expertise. And working closely with all consultants, such as architects, structural engineers, installers and subcontractors. It is largely new to almost everyone involved. This makes the preparation much more intensive. But everyone has adjusted to it and is open to it.’ Martijn: ‘To manage the risks of CLT, we have drawn up a plan. That is where those protective measures came from. But we also made a lot of optimisations, and looked at whether things could be done more efficiently. In discussions with the consultants, we concluded, for example, that the secondary walls could consist of two instead of three plasterboard panels. And it was decided not to build in timber from the ground floor, but from the first floor. In the end, we saved 20% on the contract sum with these and other changes. This is how the project became feasible.’

Grown back in 728 seconds

During the tender for Bredius, the City of Amsterdam challenged the market to submit sustainable plans. NL-Development, Ballast Nedam’s client, took up the gauntlet. ‘We were happy to respond to this because we want to do sustainable projects,’ says Arjen. ‘As a timber construction project on this scale, Bredius is a first for Ballast Nedam West. It is pioneering, and an opportunity to gain experience and expertise. In construction, we are working towards ever greater reductions in CO2. We need these kinds of techniques and methods for that. For us as a company, it is great to be at the forefront of this, especially in the market.’ When it comes to CO2 reduction, Bredius is doing well. The CLT used results in savings of no less than 2,765 tonnes of CO2. In addition, the wood comes from responsibly managed German forests. The amount required for this project grows back in just 728 seconds. Biobased at its best.

Internship on project Bredius

Angelyca is completing her internship at Ballast Nedam West, and is a perfect fit for Bredius Amsterdam with her minor in Timber Construction.

BENG star

Martijn points out that Bredius has more sustainable elements in addition to the use of CLT. ‘We use REDUXX cement. CO2 is captured during its production. Bredius' total CO2 footprint is therefore in line with the Paris Proof targets. In addition, we are drilling 43 wells under the building to a depth of 250 metres for a thermal energy storage system with heat pumps. On the roof, we will install 589 PV panels with a total peak capacity of 26,505 Wp. And during construction, we will work with as much electric machinery as possible, including the crane.’

All this means that Bredius excels in the three categories of the BENG score. In terms of energy demand, the project is 25% below the legal standard with less than 50 kWh per m². The consumption of primary fossil energy is below zero. Finally, the share of renewable energy is more than 100%. Bredius generates
more energy than it uses.

Pride

The project is also climate-adaptive (with 80 millimeters rain buffer on the roofs and in the basement), nature-inclusive (with a neighbourhood courtyard garden, green façade strips, 72 bird boxes and 160 m² of façade suitable as a habitat for bats), socially sustainable (including advancement opportunities for tenants from the neigh-bourhood) and sustainable in terms of mobility (with electric shared cars, charging points and bicycle parking).

How do Martijn and Arjen feel about working on such a project with sustainability on multiple levels? ‘I am proud to be one of the first in our company to contribute to something like this,’ Martijn answers. ‘But also of the fact that there are so many difficult challenges, and that we then succeed in tackling them together with all the consultants.’

Every project more sustainable

As a young father, Arjen likes to work on projects that ‘leave the planet in good shape. I want my children to be able to live well on it too.’ In addition, it is the knowledge and experience that make it appealing to him. ‘At Ballast Nedam West, we have been seriously studying sustainability for some time with an enthusiastic group of colleagues. We develop measurement methods so that we know how effective certain measures are. We now have a rule that we make proposals on all projects to make them more sustainable. This recently proved successful on the At The Park project in Rijswijk. Biocomposite façades will be used there instead of concrete ones.’

Next steps

Timber construction is one of the more recent steps that Ballast Nedam is taking in the field of sustainability. What do the gentlemen see happening next? Martijn: ‘There will be more projects like this, so that more field measurements can take place. This makes it possible to collect more data for even more efficient structures. In this way, sustainable solutions also become scalable and financially feasible. I also see a future for smart energy concepts.’ Arjen: ‘In addition, I think circularity will play a greater role. Then you build dismantlable buildings that you can reuse in part or in their entirety. And in addition to wood, the use of other biobased materials can be increased, such as insulation with flax. There is still quite a bit to do!’

Want to know more?

For more information and details about the project, please see this project overview.

Bredius Amsterdam

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Pioneering major timber construction