Painted Hall, The Old Royal Naval College

Client: Old Royal Naval College, Greenwich

Programme: Final phase completed 2019

Approximate Cost for all Phases: £9m

The Painted Hall at the Old Royal Naval College, Greenwich, is one of the most spectacular and important ensembles in European baroque architecture. The impressive building was completed in 1705 under the direction of Nicholas Hawksmoor, Sir Christopher Wren’s principal designer and two years later, the task of decorating the walls and ceiling of the Hall began. Conceived and executed by the British artist Sir James Thornhill the decoration took 19 years to complete.

Conservation of the murals had previously proved challenging. In 2011 a detailed survey and analysis of the paintings was undertaken which demonstrated that the paintings were deteriorating as a result of chemical instabilities both in the original painting materials and those used during previous treatments, which were all triggered by adverse environmental conditions. For two years, the team of conservators worked to stabilise and rejuvenate the paintings, with spectacular results.

Following a successful test clean in 2012, a larger project to conserve the paintings was embarked upon.

QODA were appointed as part of the team to stabilise and manage the environment within the Painted Hall to limit damage to the paintings and provide improvements to the visitor experience.

Capital works consisted of:

 

The research undertaken in the development phase of the project demonstrated that the paintings were deteriorating as a result of chemical instabilities both in the original painting materials and those used during previous treatments, which were all triggered by adverse environmental conditions.

Environmental stabilisation measures not only included the replacement of the heating system but included greater environmental buffering via the reoganisation of the visitor route to reduce the need to open the main entrance doors, new disabled access from college way, and the inclusion of internal solar shading and UV screening of the existing windows.

A range of new technologies have been introduced to stabilise the Hall’s environment, reduce energy use, and ensure the long term preservation of the paintings and fabric.

The incorporation of complex mechanical and electrical systems into such a sensitive and spectacular space required the utmost care, attention to detail, and a collaborative approach by our highly experienced team.

The original heating system utilised a single air handling unit that introduced high volumes of outside air into the hall. This system resulted in wide variations in the internal environment, particularly at ceiling level where temperature stratification and low relative humidity levels were common. The energy use associated with the conditioning of the incoming air was high and required a large air handling plant served from remote inefficient boilers located within the King Charles’s Building and associated failing heat mains.

Traditional methods of maintaining close control of temperature and humidity levels require a significant mechanical plant, requiring plant space, duct, and pipework routes which could not be accommodated without greatly altering the unique building fabric. Active humidity control is also very energy hungry and thus a passive conservation programme approach was therefore taken for the long-term care of the paintings. This included a new heating system to provide improved stability in the internal microclimate while reducing the energy use and resulting carbon emission of the building.

Following analysis that included computational fluid analysis, a heating system that utilized low level fan convectors located within the existing perimeter timber paneling was selected. Discharge air from these units is supplied at low level with supply temperatures controlled to prevent stratification.

Distribution pipework is run within the existing floor ducts below the historic marble floor. This welded steel pipework loops between the fan convector locations to provide expansion and eliminate any joints within the floor.

The key parameter that affects the condition of the painting is relative humidity (RH) which is directly influenced by temperature (T) and the moisture content of the air or the absolute humidity (AH).

The control principle adopted for the new heating system is referred to as “Conservation Heating” and has been developed by the National Trust and other heritage bodies over the past 25 years. The principle is that room heating is used to manipulate the temperature with the aim of controlling the RH within an acceptable band.

In order to maintain RH levels within the acceptable parameters it is necessary on occasions to drop the room temperatures in winter. While this approach is acceptable for day-to-day management when the hall is occupied by visitors, it poses difficulties for periods when the building is used for events, especially those which require people to be seated for long periods, such as dinners and concerts. Therefore, as well as the day-to-day conservation heating protocol, an option for temporary thermal comfort has been provided. It has been acknowledged that during the period where thermal comfort is activated this will cause RH instability, which is deleterious to the conservation of the paintings, thus it is used under strict control and on a limited basis. This approach was considered an acceptable compromise in order to allow the commercial use of the building to continue.

Because the response of the building and the paintings are unpredictable with numerous undefined variables, the operation of the system is constantly monitored and tested in the real-world conditions. From feedback obtained it has been possible to refine the control protocol.

The existing lighting within the Painted Hall and undercroft was considered to be poor. Typically, paintings and architectural features were poorly illuminated or not at all, furthermore, glare from candelabra restricted views of the paintings. There was little flexibility with the system with simple on/off switching.

Working with lighting designers Sutton Vane Associates, QODA oversaw the installation of a new lighting scheme involving re-building torchers, new lighting to emphases the wall paintings and ceilings utilizing the latest LED technology. This reduced UV radiation, provided better colour rendering and consistency, and lowered energy use and associated carbon emissions.

The building re-opened to the public in 2019 and won multiple awards including RIBA Restoration or Conservation Project of the Year, 2019, from the Museums & Heritage Awards and the Restoration of a Public Building category 2019 from the Georgian Society Architectural Award Winners.