The future’s looking bright for art
Skanska was awarded the prestigious project of renovating and refurbishing Nationalmuseum in Stockholm. Nationalmuseum was reopened in 2018, and the public was once again able to enjoy Northern Europe’s greatest art collection.
Skanska was the general contractor, in collaboration with the National Property Board of Sweden. Renovation of the main building included new visitor facilities, raising the floor in the atriums, lowering the floor in the basement, new windows, the installation of elevators, and replacing all electrical installations. We have upgraded the museum park and built a loading facility.
A careful renovation of a unique museum
This was the first major renovation since the museum was inaugurated in 1866. A number of changes were made in the 1900s, but at the reopening, visitors were greeted by a Nationalmuseum that, in many ways, has been restored to its original condition.
In the 1960s, the Annexe was added to the museum to make room for conservation studios. One of the two atriums was refurbished, and many of the windows were boarded up to protect the collections. The atrium and windows have now been opened up to allow light back into the building, and enhance the visitor experience. The new windows protect the collections and save energy.
The museum complies with the international standard for lending works of art. This includes requirements for the indoor climate, fire protection, safety, accessibility, the environment and logistics. Visitor facilities have also be expanded. Both works of art and visitors benefit from these major improvements. A number of special solutions were required in order to preserve the building’s cultural and historical heritage while simultaneously meeting all demands for modern technology.
We have been proceeding carefully throughout the entire construction process to protect the building, fresco paintings by Carl Larsson and other irreplaceable craftsmanship.
Careful construction process
The project commenced in August 2014. We covered the sections that require protection and performed other preparatory work. It was essential to protect this historic building from water, vibration, dust, subsidence and other elements of the construction process. This was followed by earthworks and foundation construction for the new loading facility.
– Since this is a waterfront site, we installed retaining walls and then excavated until we reached the groundwater table. Then we lowered the water table inside the walls to avoid having to excavate wet loads. At the same time, we sawed off 12 meters of the Annexe to make room for the loading facility, says Pontus Lindeberg, Project Engineer.
The concrete structure in one of the atriums has been demolished to restore it to its original condition and allow the light back in again. The boarded-up windows in the main building have been reopened and replaced with modern versions.
Better climate for collections and visitors
Modern demands on the indoor climate in museums are high. Preservation of the collections requires ideal temperatures and relative humidity. These levels are controlled by a system that is sensitive to variations caused by weather conditions and the number of visitors. We have replaced all installations in the building and significantly extended the climate-control system.
The Swedish National Heritage Board set demanding requirements for how this should be implemented, which affected us in terms of the methods we chose, financial constraints and time. During the design stage, several special solutions were created that conceal the technology in smart ways.
The new and modern climate-control system can measure relative humidity and room temperatures, and maintain ideal levels. Skanska delivered a total solution. Fredrik Johansson, Project Manager, describes the challenges posed by the installation of a climate-control system:
– We were not permitted to change the layout of any of the rooms, and the size of shafts was highly restricted. Concealing so many space-consuming installations is not easy. We reused all vertical shafts. We also installed a new duct system underneath the floors. This involved lifting the flooring, installing ducts and relaying the flooring.
Air flows into the rooms through custom-made ceiling medallions in the beautiful domed ceilings. These medallions also serve as ceiling sprinklers, thereby concealing two practical features in one beautiful detail. Such smart solutions provide Nationalmuseum with an indoor climate that is ideal for both collections and visitors.
Basement dug out
The floors in the atriums were raised to improve accessibility at entry level. At the same time, the floor was lowered in the basement, which was previously no more than standing height. New visitor facilities were created in this area, including toilets, wardrobes, stroller parking and a picnic room. We also built several new ventilation and electrical equipment rooms, as well as a large kitchen on this level.
Since the entire building stands upon rock, the project required rock and soil excavation under the building. We were blasting very gently to prevent subsidence.
Nationalmuseum is a unique project in many ways.
– The chance to refurbish a property of this caliber only comes along once in a lifetime. The project group was very committed, and we all have great respect for the building. We also enlisted the services of an antiquarian expert. Respect for the building means that we were working even more intensively than usual to prepare each stage, says Fredrik Johansson.
An environmentally friendly and green museum
In partnership with the National Property Board of Sweden, we worked to create an environmentally friendly and green museum. The refurbishment maximizes energy-efficiency for Nationalmuseum, and the National Property Board of Sweden decided to certify the building under the EU’s GreenBuilding Program. This meant that the building’s energy consumption had to be reduced by at least 25 percent.
The building’s cooling needs are met by locally produced deep water source cooling. Selected energy-efficient electrical installations and the new windows help to reduce energy consumption.
The renovation of Nationalmuseum also complies with the Silver-rating requirements of the Sweden Green Building Council, to the furthest possible extent. This environmental performance classification covers the areas of energy-efficiency, indoor environment and materials. The Sweden Green Building Council system is not adapted for the certification of older historic buildings.
During the demolition work, hazardous substances that were used in the past were uncovered. We decontaminated all sections that we could access, documented the building materials we used and made sure that hazardous substances were removed.
Project in figures
- 5,300 cubic meters for added installations, equivalent to 52 city buses.
- 2,300 square meters for expanded visitor facilities, almost as much as 12 tennis courts.
- 300 windows were renovated. Some inner windows weigh 800 kg.
- 22 white-collar workers were involved in the project. A maximum of about 200 skilled workers were on site.
- 75 meters – the depth by which the floors were be lowered in the atriums.