Sustainable Cities™

Copenhagen: Renovation has reduced energy consumption by 73% in Ryesgade

One property in the street of Ryesgade in Copenhagen provides an excellent example of how to improve functionality and sustainability and to achieve significant energy savings without compromising the building’s cultural history. The property has been energy-renovated and has also been supplemented with penthouse flats and roof terraces.

Ryesgade 30
Photo: Carsten Ingemann

Sustainable combination

Denmark's 600,000, traditionally built multi-storey buildings from the period 1860 to 1960 account for a large portion of our energy, when they are heated. They have not received the same attention in terms of the energy-saving debate and efforts as newer buildings.

In Ryesgade, the combination of the renovation and the creation of penthouses serves as a "double" sustainable solution. There is a saving of energy in the existing dwellings, because the new penthouses constitute highly efficient insulation of roof and ceilings. The project also creates "penthouse-based urban densification", expanding the city upwards instead of outwards. This is an advantageous solution: the most sustainable building is that, which does not require any building.

Technical details

The facades of the property are worthy of preservation, so radical external re-insulation was out of the question. But experiments with the indoor climate of the dwellings and internal re-insulation have yielded an impressive result. Energy consumption in the property in Ryesgade has been reduced by 73%. With 43.5 kWh/m2/yr., the building almost achieved the intended low-energy class 1 (35.4 kWh/m2/yr.), whereas consumption prior to the renovation was 162 kWh/m2/yr. 

The indoor climate of the dwellings was improved by installing a central ventilation system in two stairways and a de-central system in one stairway. The systems are controlled in relation to actual needs, so they provide an excellent indoor climate with no unnecessary loss of heat. When the amount of CO2 drops in a flat, the system almost shuts down, and when there are people in the flat again, it is activated. The heat, which is extracted, is recovered and used to heat up the intake of fresh air in the dwellings, thus avoiding drops in temperature and draughts. Together with the insulation of water pipes, the ventilation systems have reduced energy consumption by 20%.

Inside, the flats were clad with a 5-cm thermal envelope, before restoring the original plaster. In tandem with the Class A windows, the internal insulation has reduced energy consumption by 27%. Exterior insulation of the firewall against the neighbouring property, together with the horizontal division towards the basement and the insulating effect of the penthouse flats, has reduced consumption by 21%. The remaining 5% of the reduced energy consumption has been created by solar panels on the roof. 

Ryesgade Photo:

The effect, energy consumption, "operational friendliness" and indoor climate in Ryesgade will be recorded and measured in the course of this year. But technologies do not do all the work by themselves. The behaviour of the residents also has a significant impact on energy consumption. That is why it is important to record statistics and provide guidance for the best possible use. 

More housing in Copenhagen

It is not a straightforward affair to make such radical upgrades of buildings' energy class. If one is to realise the full potential of roofs, then the municipality must change their focus from the limitations of the past to options of the present, kissing goodbye to older forms of roofing. If one deploys the type of project utilised in Ryesgade, the sale or rental of new penthouses can lead to profits, which can then be used for the renovation of the building below. The typical blocks of flats in Copenhagen from 1850-1950 are completely brick-built, so can easily support one or two more storeys. The Technical University of Denmark have calculated that it is possible to establish enough, new penthouse flats to accommodate 20,000 residents. This amounts to approximately a quarter of the 100,000 new inhabitants, who are expected to move to the capital in the course of the next 10-15 years.

Copenhagen's older blocks of flats provide a unique opportunity to show the world that, by means of the innovative development of buildings and housing blocks, we can combine strong cultural heritage values with excellent indoor climate, ambitious environmental and energy-related considerations, providing attractive residential and urban environments for the citizens of tomorrow.

Thursday, October 03, 2013 / By Nina Kirstine Busk

Last updated Tuesday, June 24, 2014