AR0821 Materialisation: Future Envelope (2020/21 Q3)

DE ZALMHAVEN

The project 'De Zalmhaven' in Rotterdam consists of a residential tower of approximately 215 meters high (De Zalmhaven I), two residential towers of approximately 70 meters high (De Zalmhaven II and III) and a plinth with two rows of family houses on Houtlaan and Gedempte Zalmhaven. The family houses enclose a four-storey communal parking garage with an entrance and exit on Houtlaan. A roof garden will be built on the roof of the parking garage, which is accessible to all residents of the complex.

In this report, we will focus on the two mid-rise towers, Zalmhaven II and III, by KAAN architecten.

Location: Scheepvaartkwartier, Gedempte Zalmhaven, Rotterdam

Architects : DAM & Partners Architecten (high-rise)

KAAN Architecten (mid-rise)

Client/Developer: Zalmhaven CV, Amvest and AM

Contractor: BAM, Bouw en Techniek Grote Projecten

Year of design and completion: 2015 - 2022

Size: Zalmhaven II & III 35.000 sqm

Program: 452 apartments

33 single-family homes

1380 m2 offices 950 m2 horeca and facilities

DE ZALMHAVEN

- The Zalmhaven towers II and III are accessible from the Gedempte Zalmhaven.

- The family houses have their own entrance at street level.

- The entrance and exit of the parking garage is on the Houtlaan.

Family houses

Car parking & rooftop garden

Family houses

Gedempte Zalmhaven

Houtlaan

CONTEXT / URBAN PHYSICS

The Zalmhaven towers are located on a site adjacent to the former harbor of Zalmhaven, in the center of Rotterdam, between Het Park and the Erasmus Bridge / Maas river. The common wind direction in this area is South-West.

CONTEXT / URBAN PHYSICS

De Zalmhaven is situated within a dense urban context on the border of low rise and high rise in the city centre. Rotterdam has a big Urban Heat Island (UHI) problem causing the city centre to heat up during the summer days and radiate heat at night. Although the towers are situated close to the water and relatively near green parks the accumulation of tall buildings and lack of green ratio to buildings cause a lot of heat to be trapped between the buildings.

In this radiation analysis, the surrounding influence of the buildings is not taken into account. The map shown in fig.1 is based on the old situation before the construction of De Zalmhaven but you can already see that the plot has a high level of heat accumulation.

The south-oriented facade absorbs the most radiation which heats up the metal sheet cladding as shown in fig.2. In the first plan, the choice of cladding was concrete which would add to the heat accumulation of the building and contribute to the UHI effect. A lot of sun is directed at the flat roof of the apartments and parking garage. This radiation heat is reduced in the design by the roof garden situated between the towers.

Fig.2 Radiation analysis SE view (own image)

Fig.3 Radiation analysis NW view (own image)

Fig.1 UHI effect Rotterdam

ARCHITECTURAL CONCEPT

The two mid-rise towers, Zalm haven II & III, consist of a solid plinth. The plinth includes clearly marked entrances of the complex and family houses. On the roof of the plinth building are rooftop gardens for the family houses and there is a public roof park for the apartments in the towers. The plinth building has a direct relationship with the neighbourhood. The footprint of the two mid-rise towers is a split and shifted square. This creates more corners and apartments of different sizes with windows offering beautiful views.

Façade composition

The façade of the Zalmhaven towers II & III show a noticeable grid. The grid is also seen in the plinth of the complex. The grid façade relates to the traditional, sober architecture of the old shipyard. Besides that, the grid is a binding motif. It links up the various blocks into a whole. The balconies are placed above each other in one line. So on each side of the towers (so on each façade) a line of balconies is visible. In this way, the balcony’s are providing verticality and the focus of the façade is on the verticality.

Offset of the floorplan

Architectural concept

ARCHITECTURAL CONCEPT

Glass

Anodized brass aluminium

Folded white aluminium

Materialisation of one single unit

FRAGMENT

MATERIALIZATION

1. In/situ concrete

2. Prefab concrete wall

3. Glass wool insulation

4. Insulation plug

5. Window frame

6. Folder aluminium cladding

7. SA-L-OUT water resistant foil

8. Sa-L-IN

9. Liquid rubber

10. Black rubber seal

11. PUR

12. XPS Hard insulation

13. Angle steel profile

14. Steel strip

15. Drive screw

16. Self-tapping screw

17. Concrete screw

18. Self-tapping concrete-screw

19. Insulation floor

20. Triple glazing

21. Cladding anchors

22. Steel cladding rail system guides

23. Steel cladding rail system

24. Floor heating mortar floor

MOST INNOVATIVE BUILDING PARTS

Although the façade was initially designed with cast concrete panels framing the window as a whole component the design was later changed to aluminium panels. To ensure the architectural concept both panel options have channels bordering the window and creating a grid on the façade. In the concrete option, these channels were mainly aesthetic and maybe to reduce some of the material use. In the aluminum design the channels have two function:

1. STIFFNESS - Like steel composite decking floors the panels are much stiffer due to the chanels.

2. TOLERANCE - Expansions due to heat can partially be absorbed in the harmonica like channels that widen and contract with the thermal changes preventing the panels to bulge out on warm days.

3. HEAT RADIATION - By increasing the surface area of the panel by adding the chanels, accumulated heat is radiated faster to the surrounding air cooling the façacade surface.

Assembly

The facade panels are made up of four separate parts which are screwed together to appear as a singular panel on the façade.

1. A sheet of aluminum is cut to 292x3050x5.

2. The panel is folded four times to create the chanels making the panel 260x3050x50.

3. The angles of the both sides of the panel are marked.

4. The ends of the panels are cut down.

5. The top and bottom part are welded to panel parts to make the corner. The welding is sanded down to form a uniform surface. Holes are drilled in outer strips of the panels both inside and outside.

6. The painted panel is placed on the facade and fixed in place with drive screws to the window frame and steel rail system

7. First the toppart of the panel is attached to the facade and while removing the scaffolding the bottom part of the panel is placed. All panels are lined with a rubber tape to accentuate the facade grid.

FACADE STRUCTURE

The structure that supports the aluminum cladding of the facade is supported on the external edges by a steel rail system composed of: Steel anchors directly inserted into the primary concrete structure. Steel profiles / guides connected to steel anchors. Steel rails held by steel guides. And on the internal edges, by the aluminum frame of the window, which is connected to two steel brackets, which are connected to the main structure.

This diagram shows the absorption and distribution of the wind force towards the main structure of the building. The horizontal force distribution applied to the aluminium cladding is partially distributed through the steel railing system and through the window frame to the main concrete structure.

Wind force

Steel railing system: Anchors, guides and rails. Connection between rail system and the aluminium cladding.

Bottom window bracket. Top window bracket.

Steel counter rail 3000x50x5

Steel rail guide 100x60x5

Magnelis steel profile 60x100x4 Steel strip 250x240x12

FACADE FIXING SYSTEM

The primary structure of the façade is made up of horizontally placed steel profiles (60x100x4) on the top and a bigger steel profile (250x240x12) on the bottom part of the window opening. The profiles are placed on the outside of the concrete to maximizing inside space and holding the window frame. The profiles are held in place by concrete screws (10x75) which are placed in pre-drilled holes. The bottom profile is fixed with Etanco BARACO FM 753 a steel concrete anchor which expands when tightening the nut on the exterior side.

The aluminium window frame (secondary structure) partially supports the aluminium paneling on the façade exterior and transfers the wind and dead load through the steel profiles on to the structural concrete floors and walls primary structure).

To gap the space between two window frames and panels a steel rail system is used. It is held in place by steel pins which are drilled in the primary structure and transfer wind and dead load of the aluminium paneling directly to the concrete structure.

Primary structure

In-situ concrete

Secondary structure

Window brackets

Window frame Secondary structure

Rail system cladding

Aluminium cladding

BUILDING PHYSICS

Fig. 1 Lines of defence

Fig. 2 Pressure equalization

BUILDING PHYSICS

Thermal performance

Insulation

Insulation of the façade is guaranteed by 137 mm thick glass wool panels, in the opaque parts of the façade. Glass wool insulates the façade thermally and acoustically as well. The insulation of the façade in the open parts is guaranteed by triple insulating glass (6-18-4-18-4) with an E -coating and filled with Argon.

U- & R-value

The thermal performance of the façade has been investigated by calculating the Rc-value and the U-value of a closed and an open component. The values of each component have been compared with the standard values from the Bouwbesluit.

For the opaque component, the aluminium cladding has not been taken into account. The contribution would not have influenced the Rc-value in a significant way. The aluminium cladding

performance of transparent part of the façade.

BUILDING PHYSICS

The gaskets and seals are necessary to prevent or manage air and water intrusion.

The second gasket excludes most of the rainwater, but any water that passes through is drained away at the bottom of the aluminum profile to the outside. The air seal gasket, internal barrier, serves as an air seal rather than as a full weather tight seal. An additional function of the gasket seal is to provide a continuity with the thermal break

BUILDING PHYSICS

Acoustic

The facade is adequately insulated with the implementation of Glass Wool insulation and with triple glass windows.

The apartments are provided with a so-called acoustic mortar floor, which will improve interior acoustics. When connecting to the walls, window frames, pipes, etc. the floor finish thereof must be kept acoustically free. The architectural ceiling is part of the acoustic provisions to prevent sound leaks.

Most of the balconies have a sound-absorbing finish on the underside, to reduce acoustic reflection in interior spaces.

Ventilation

The general circulation areas of the residential buildings (corridors and vestibules) will be provided with a mechanical ventilation system with filters and heat recovery. For the storage rooms in the basement, air supply and exhaust systems are also installed in certain places. Air is supplied directly from the outside, exhaust is blown out into the parking garage. The lift shafts are naturally ventilated, for this purpose roof caps are placed on the roof outlets.

A ventilation system is installed in the apartments based on the mechanical supply and discharge of air .The mechanical supply and discharge take place via a motorized ventilation box in the storage / technical room, a so-called heat recovery unit. Ducts are installed in the concrete floor constructions from the HRV unit. The channels transport the air to the relevant rooms, where the air is blown into the room by means of rosettes. The air is extracted in the kitchen, sanitary rooms and installation location of the washing machine by means of rosettes and returned via air channels through the concrete construction to the heat recovery unit for heat recovery. The extraction valves are adjusted per room. There is a central position switch in the kitchen.

The channels of this system are concealed in the floors and in the shafts as far as possible.

Aluminum and glass window, manually adjustable from inside the building.

Mobile aluminum and glass window, adjustable from the inside and outside to communicate the interior areas with the balconies.

Mobile aluminum and glass window, adjustable from the inside.

Aluminium and glass terrace door

Aluminium and glass front door.

FIRE SAFETY

Materials and classification

In NEN-EN 13501-1 a fire classification of construction products and building elements is described. The classification is divided into class A1 to class F, at which class A1 is the highest and safest one. The façade of the Zalmhaven is longer than 13 meters and higher than 2,5 meters, therefore all the materials in a construction would have to be of level B or higher. In the figures below the classification of the main construction materials are represented. This sketches the fire safety of the façade.

Concrete | fire class A1 / A2

The concrete walls and floors are incombustible

Isover multimax 30 ultra | fire class A1

The multimax 30 ultra insulation consist of glass wool. Almost all the products of ISOVER belong to fire class A1, also regarded as incombustible.

Aluminium cladding | fire class A1

Aluminium panels are incombustible. The melting point of aluminium is 659 degrees, so the aluminium cladding will melt.

XPS insulation foam| fire class E / F

The XPS insulation foam is very combustible. The material is as regards fire safety a bad choice.

Flashover situation

According to NEN 6069 the fire resistance between the floors, in both directions, has to measure up to criteria EI, the toughest criteria to get. This can be achieved easily in the Zalmhaven-towers because of the massive concrete floors. Concrete is proven to have a high degree of fire resistance. It cannot set on fire and doesn’t emit toxic fumes when affected by fire. The fire resistance of the façade, from the inside to the outside and reversed, has to measure up to criteria EI as well.

The façade is mostly build-up of concrete which is a fire-resistant material. Also the steel angle profile will block the fire. The PUR-foam and the XPS insulation, on the other hand, are highly flammable and a critical point in the façade. However, there only is a small amount of insulation fixed in the façade so which vastly reduces the risk of fire spread. Besides that, the mineral wool will block the fire. The aluminium cladding is as most parts of the façade incombustible. It will melt after a while. Overall there is a low risk of fire spread in the façade.

CIRCULAR ASPECTS OF FACADE

Reusability vs. Durability

The choice for aluminum cladding has several sustainable benefits compared to the concrete option. But while aluminium has a much better reusability, concrete has much longer lifespan and ages more aesthetically then the aluminium cladding.

A benefit of the thin aluminium facade is that it leaves more room for insulation, improving the Rc value of the whole facade. It also leads to less heat accumulation within the outer facade cladding and reducing heat radiation which can cause an Urban Heat Island effect. Another benefit of the lightweight aluminum elements is that they are easily replaceable. Making maintenance on the facade less of an effort. Faulty panels can be easily switched out without deployment of a construction crane.

Although the aluminium cladding is easier to recycle the question remains if the building will uphold its aesthetic standards in the long run with this choice of material. The aluminium facade which is made up of four times as many elements as the concrete option is vulnerable to shifts due to thermal expansions and wind load. With almost no tolerance for movement put in place this could mean that the neatly structured facade becomes messy overtime making it less appealing and will need more maintenance.

The question remains what is more important in the near future reusability (aluminium) or durability (concrete)?

1. In-situ casted reinforced concrete structure, primary structure. Concrete casted through with tunnel construction method.

2. Installation of facade cladding anchors, directly screwed in the primary concrete structure. Installed manually from the exterior with the help of scaffolding.

3. Installation of the bottom a top brackets for the window frame. Installed manually from the exterior with the help of scaffolding.

4. Mounting of the aluminum prefabricated window frame. Installed manually from the exterior with the help of scaffolding.

5. Mounting of glazing from the inside. Installed manually with a glass vacuum lifter.

6. Securing the glazing with window gasket from the interior.

7. Insertion of XPS hard insulation on top of the window frame. Installed manually from the exterior with the help of scaffolding.

8. Installation of water resistant DPC foil around the window frame, ensuring air and water tightness. Installed manually from the exterior with the help of scaffolding.

9. Installation of Glass Wool insulation around the window frame covering the entire structure. Installed manually from the exterior with the help of scaffolding.

10. The insulation panels are secured with insulation plugs directly connected to the primary concrete structure.

ASSEMBLY SEQUENCE

11.

14. The facade assembly concludes with the mounting of the horizontal cladding panels. The horizontal panels are installed as the last element since the scaffolding structure is secured in the hole designated for this element. By synchronizing the dismantling of the scaffolds with the placement of the horizontal panels. Installed manually from the exterior with the help of scaffolding.

15. Sealing of the joints with rubber band tape to ensure the third line of defense of the facade against rain and for aesthetic reasons. Installed manually from the exterior with the help of scaffolding.

16. Once the installation of the façade is completed, the installation of the floors of the interior spaces is continued. The first step consists of the placement of hard insulation on the

Mounting of the guides for the facade cladding railing system. The guides are connected to the cladding anchors installed in step 2. Installed manually from the exterior with the help of scaffolding.

12. Installation of the cladding railings on to the railing guides with screws. Installed manually from the exterior with the help of scaffolding.

13. Mounting of the vertical facade cladding panels on to the railing system and the window frames with screws. Installed manually from the exterior with the help of scaffolding.

concrete base.

17. Finally, the mortar floor is cast in conjunction with the installation of pipes for floor heating.

FACADE ASSEMBLY

REFLECTION AND CONCLUSION

It was an interesting process to analyse the facade solely from one visit and from pictures we took during that visit. During our visit, one tower had just been finished and the other was halfway finished with the scaffolding still in place. As in the pictures on pag.10 every assembly fase was visible. It was a lot of discussing and assuming in the first 4 weeks because this was the only source of information we had and it was interesting to compare our results with the actual facade details which we received in the last week.

An interesting aspect of the facade design was that in the original design the facade cladding was concrete precast elements which later changed to the demountable aluminium cladding it is today. During this change of the design, the overall aesthetics of the facade changed very little while the underlying structure and thermal performance of the facade changed significantly.

Aluminium VS. Concrete

The switch from concrete to aluminum paneling was probably made because of economic reasons with the aluminium being a lot cheaper and easier to assemble in situ cutting down on construction time and machine work.

Although the aluminium cladding is easier to recycle the question remains if the building will uphold its aesthetic standards in the long run with this choice of material. The aluminium facade which is made up of four times as many elements as the concrete option is vulnerable to shifts due to thermal expansions and wind load. With almost no tolerance for movement put in place, this could mean that the neatly structured facade becomes messy overtime.

The facade could be considered a fake facade as it mimics the original single element concrete facade of the original design. The giveaways are the seams of the four aluminium parts and the still visible screws that hold the aluminium facade in place.

During our analyses, a problem with water infiltration through the window frame was discussed. It is unclear if some of the problems with water infiltration in the window frame, are caused by the sudden change of the facade structure or if they were also included in the original design. The proposed solution was redesigning the taping pattern of the SA-L-OUT water-resistant foil to broad strokes with more flexibility at the corners. This approach of taping the window frames to make them watertight causes a lot of work to be done in situ and increases the risk of errors. A redesign of the window frame fixing to prevent water infiltration is needed.

One of the most interesting finds was that the shape of the facade elements with the channels, which did not change in the new design, only have benefits when they are made out of aluminum. The way the channels provide thermal tolerance and rigidity only work in the aluminium design

In conclusion, it was an interesting process analysing a facade in such detail while discussing it with professionals. It was interesting to hear their take on this facade and what they liked and what they thought could improve.

In this course, we learned analysing by looking and understanding the different factors that are taken into account when designing a facade on every scale level. This course is what is missing in the bachelor because it bridges the gap between understanding the generic detail and truly understanding the more technical side of facade design and feeling more comfortable using this knowledge to make a realistic and functional facade.

KAAN Architecten - De Zalmhaven