According to the European Commission, at least 35% of buildings in the EU are 50 years or older, and Europe’s historic buildings are well-known for not being very energy efficient. They consume large amounts of electricity to light spacious rooms and hallways, and receive expensive bills for heating, or cooling, while lacking proper insulation. The Commission also found that service buildings, such as Lisbon’s city hall, are on average 40% more energy intensive than residential buildings.

Such numbers make it evident that it is crucial to find energy efficient solutions for these buildings to make a significant contribution to reaching the EU’s new target of a 55% reduction in emissions by 2030 – part of the Renovation Wave Strategy.

Typical renovations aimed at increasing the energy efficiency of a building would start by working on insulation.  However, insulation material would have ruined the iconic facade of the city hall and was too complex to be integrated indoors within richly gilded walls and ceilings. This left the windows and doors to improve. Again, the standard go-to solution, double-glazed aluminium or PVC windows, would not work for the city hall as the 100 windows could only be restored, so the final choice fell to renewing the existing wood frame and adding a thicker single glaze.

While the installation of the new heating, ventilation and air conditioning system, and the replacement of the 2,000 chandelier light bulbs with Light-emitting diode (LED) technology were not contentious, the installation of solar panels spurred more negotiations.

The National Directorate was concerned about the visual impact that this technology could bring in terms of several panoramic views of the city. The project team procured panels in a darker colour to better blend with the roof tiles, and they carefully and strategically positioned them for sensible architectural integration.

The  lead agency for the project is the City of Lisbon together with  multiple stakeholders including the Energy and Environment Agency, Lisboa E-Nova, who was the  overall coordinator of the implementation tasks of the Sharing Cities project. They coordinated their efforts with Portugal’s Directorate-General for Cultural Heritage, charged with protecting the country’s historic treasures. With the help of digital models of the city hall created by the Technical University of Lisbon, they discussed solutions and found agreements.

Heritage building works are much more expensive than normal building works, not only because of the technical solutions that have been implemented, but due to the heritage proctocols s that companies have to follow to ensure the correct implementation of the different measures.

Lisbon’s payback time is around 10 years for the €420 thousand invested by the city, with an additional €168 thousand EU funding received through the Sharing Cities project.

While the analysis is not yet definitive, and the final impact of the renovation will be clearer with a few more years of monitoring, the numbers so far are promising. The energy consumption went from 493.72 MWh annually in 2016 (before the renovation started) to 246.93 MWh in 2019, after all solutions were implemented, a 50% decrease equivalent to 84 tons of CO2 emissions reduction.

As most heritage buildings are protected; owners have to overcome additional barriers such as strict heritage protocols and codes that make them complex to renovate.

This is an issue that the ROCK project has raised in its ‘Recommendations to decision and policy makers’, calling for creating a balance between flexibility and regulation. Based on the experiences from the project, which Lisbon is also part of, cities must be allowed to balance protection and preservation of cultural heritage with flexibility and innovation, and decisions should be based on impact assessments and stakeholder participation.

For cities that are planning similar historic renovations, Lisbon municipality suggests starting with a building assessment clearly laying out the baseline energy performance, along with what can be done and what the cost savings would be. Cities should also involve all national engineering or heritage authorities from the beginning to avoid bureaucratic surprises, and to ensure all procurement requests have the right details and restrictions.

Eurocities: A green make-over for heritage buildings

https://eurocities.eu/stories/a-green-make-over-for-heritage-buildings/