Kokoon modular housing

Kokoon is a modular living unit built to address the acute shortage of temporary accommodation for asylum-seekers, students and residents displaced by building renovations. The prefabricated modules were designed as a living solution that can be easily transported and stacked in various configurations in order to fit numerous sites in urban and suburban contexts. Kokoon was one of the winners of Metsä Wood’s Open Source Wood award.

Kokoon modules have the potential to be mass-produced and assembled as multi-unit housing complexes. Kokoon’s three initial prototype units were designed and constructed by the Aalto University Wood Program team in Finland. They were prefabricated at the Aalto University Architecture workshop in Otaniemi, Espoo. Design of the units started in January 2016, and construction began in April 2016. The units were completed in a couple of months.

When it came to design development, the team explored several wooden materials for the construction of the modules. However, the material efficiency of Kerto® LVL (laminated veneer lumber) allowed for minimal wall profiles to optimize the limited footprint imposed by the project parameters – a comfortable living unit that can fit on the bed of a truck for ease of transport. LVL not only provides the primary wall structure and the floor and roof substrate, it is left exposed as the interior finish, which reduces the layers of assembly and construction time. Kerto LVL Q-panels allowed for fast module production and offered the required load-bearing capacities. As a wood product, the extensive use of LVL also contributes significantly to the overall sustainability of Kokoon.

Kokoon rewarded for innovation

“I think this is a great idea showing how modular living can help in temporary housing for families. In the future, it may be possible to order a temporary house, just for a few weeks, delivered to your doorstep,” says Frank Werling, Head of Technical, Engineering and Design, Metsä Wood, who is a member of the award jury. “This concept is an example of how to achieve flexible and functional temporary accommodation with Kerto. Kokoon modules are also adaptable for larger housing units and on an industrial scale,” Werling continues.

Prefabrication with Kerto LVL for efficiency, precision and sustainability

In the Kokoon project, prefabrication allows the majority of construction to occur off-site in a climate-controlled environment. This improves the working conditions for the team constructing the modules and enables easy assembly of the elements’ interior layers, without the need for expensive onsite weather protection. Building on the ground as one-storey modules allows workers easier access to areas that would be hard to reach if the three-storey structure was built at the site. Prefabrication allows efficient mass production of the modules.

“As an architect, how we manage the quality of building from start to finish is an incredibly important part of the equation,” says Philip Tidwell, a teacher in the Wood Program at Aalto University. “Prefabrication gives us possibilities to minimize the construction time on site, and to improve the final quality of the product we are providing to our users.”

Self-supporting modules

The prefabricated modules are structurally designed to be self-supporting, as well as supporting the weight of up to two modules above. The efficiency of Kerto LVL Q-panels allowes for a relatively compact wall structure of 45 mm Kerto LVL studs on 45 mm Kerto LVL panels, which also serves as the interior finish. Four glulam columns, one at each corner, transfer the load down through the assembled modules. Additional diagonal bracing is not required due to the strength and stiffness of the Kerto LVL Q-panel, which allows the walls to act as shear panels.

The cavities between the LVL studs were filled with cellulose insulation, and 25 mm wind barrier board was installed over the assembly. Battens and solid wood cladding panels, painted in deep red, finish the exterior. The roof and floors were composed of LVL beams and solid wood joists, with Kerto LVL Q-panel sheathing on the interior face. Kerto LVL, treated with a protective waterproof coating, was used as the roof substrate, and a roof membrane and sheet-metal flashings were installed over this substrate.

Simple joints bring cost savings

The details were relatively simple. Most connections were standard screw or nail connections typical of rough carpentry, while the critical connections between modules, at the four load-bearing glulam columns, required a steel plate. Working with Kerto LVL streamlined the construction time and cost by eliminating complex connections that require specialized machining or carpentry. On a mass-production scale, this would translate to exponential savings.

Light structure to transport

The modules have proven to be relatively easy to disassemble and transport, having been relocated four times to different sites around the Helsinki area. In June 2016, the Kokoon modules were transported to their first site on the grounds of the Museum of Finnish Architecture and were assembled in one day.

When the exhibition ended, they were transported to the grounds of the Flow music festival on the other side of Helsinki to be on display during the festivities. Last, they were moved to their current home in Otaniemi. Even though they have been lifted and transported several times, the rigidity of the modules has allowed them to remain in excellent condition.

Wooden interior creates welcoming feeling

Public reaction to Kokoon has been very positive – there have been many requests to move in! The unique exterior form and distinct cladding provide an initial draw, but it is the exposed Kerto LVL Q-panels on the interior that provide a warm, airy feeling that is an unexpected treat for visitors to Kokoon. The interior feels much larger than the exterior suggests, and this is largely due to the skylights washing the exposed LVL in daylight.