Stora Enso’s innovative office-hotel concept was designed with adaptable structural and building service solutions

Stora Enso aimed to develop a globally unique timber frame concept that allows for adaptable construction of both hotel and office spaces within the same hybrid project. Sweco designed the structural and building service solutions for the concept.

Stora Enso initiated the development of the versatile timber frame concept in collaboration with Sweco and INARO Integrated Architecture Office in the autumn of 2022. According to Susanna Friman, Project and Group Manager at Sweco, there has been a long history of successful collaboration with Stora Enso on various wooden construction projects over the years.

“Stora Enso has also developed dozens of concepts that facilitate the work of designers in modern mass timber construction.”

The goal was to create a structural concept for the rapid construction of an adaptable hybrid building. The biggest challenge was that the concept building had to seamlessly combine both office and hotel spaces.

“For example, ventilation, sound insulation and fire safety requirements vary between office and hotel spaces, so we had to find a working compromise for both,” Friman explains. At the same time, the goal was to maintain the adaptability and space efficiency of different floors, which prolongs the building’s lifecycle. “Space changes should not require changes in the ceiling height of the rooms.”

Taking building services into account helped maximise the amount of wood used

According to Friman, right from the beginning of the concept development, they wanted to involve building services engineers at the same table. “Taking building services into account is especially crucial in timber construction to ensure that technical space reservations do not conflict with e.g. column and beam alignments.”

The solution was found nearby. Sweco’s building service engineers joined the concept development process to collaboratively create a realistic, functional and sensible overall solution.

“We were able to influence the choices right from the architecture to the location of technical pits, so we were able to allocate sufficient space for building services,” says Nico Haavisto, Department Manager at Sweco. At the same time, a cost-effective outcome as per the client’s wishes without compromising was ensured.

Together with building service and structural engineers, as well as the architect, they were able to maximise the use of mass timber. This reduced the amount of concrete structures and reduced the carbon footprint of the concept building. According to Stora Enso’s calculations, a 7-story building based on the concept stores 408 tonnes of carbon during its lifecycle and produces 19% fewer carbon dioxide emissions compared to an equivalent concrete building over its entire lifespan.

The structural solution is adaptable to user preferences

In addition to functional goals, the concept building aimed to maximise the use of Stora Enso’s products. Structural engineers meticulously reviewed about ten different structural solutions. The alternatives were systematically narrowed down. “We clearly defined the cause-and-effect relationships for different solutions more rigorously than conventional design,” Friman explains.

The chosen concept features a flexible and modular slab-beam-column design that enables open and adaptable spaces. The timber frame utilises Stora Enso’s Sylva product family, including CLT and LVL elements, as well as LVL and GLT laminated timber beams and columns. Concrete is only used in stairwells.

Clear building service solutions

According to Haavisto, the aim in building services was to provide solutions that leave as many functional alternatives as possible for the design phase. “However, the location of technical pits and sewer lines, floor-specific space solutions for building pipelines and ducts, and other major alignments have been determined, which speeds up the subsequent planning.”

Traditional radiator heating proved to be the most adaptable heating method. Cooling can be achieved by utilising ventilation and cooling beams, among other methods. “We did not want heating or cooling pipes in the floors because they are not sufficiently adaptable solutions.”

Technical pits are located at the ends of the building, which differs from the typical multiple technical pits in hotels. The HVAC machinery rooms are located in the attic. “Air is distributed to the rooms from the central corridor’s HVAC ducts, and the air volumes have been predetermined in relation to the number of people in different spaces.”

An internationally replicable concept

Stora Enso’s ready-made “Mixed use, flexible and adaptable” concept is designed to work across Europe. The solutions have been intentionally designed to comply with Finnish regulations. “If the building services concept works in Finland, it is likely to work elsewhere,” says Haavisto.

Friman agrees. “Our structural design requirements are the strictest in the world. When we design a structure to function in Finland, it will function in almost any part of the world.”

This unique concept is seen as having significant international potential. It allows for the rapid creation of low-carbon and adaptable working and accommodation spaces. Friman believes that it can support the global transition of the real estate and construction industry towards sustainability. “The concept has the potential to create export markets for both wood product deliveries and timber construction design expertise.”

The concept has been piloted in Stora Enso’s new headquarters, Katajanokan laituri.

In addition to Sweco and INARO Integrated Architecture Office, the development of Stora Enso’s concept also involved Ramboll Finland Oy, Wood Expert Oy and KK-Palokonsultit Oy.

Pictures: Stora Enso