The Great Hall, Edinburgh Castle

Context

This is one of the main parts of the hugely popular Edinburgh Castle. It sees well over 1 million visitors each year and is regularly used for functions. It is a mixture of medieval building and Victorian restoration. Much of the medieval ad post medieval weaponry is on loan from the Royal Armories.

The building is in a very exposed location and experiences temperatures well below zero and very high winds at times. The visitor numbers make it impossible to close the doors for much of the time.

The cast iron heating system forms part of the aesthetic of the building and is difficult to improve upon. It is occasionally, under instruction from non-conservators, supplemented with very powerful (22 kilowatts each) electric heaters to provide comfort levels of heating.

Issue

The wooden panelling, painted timber ceiling, oil paintings and weaponry are all susceptible to fluctuations in relative humidity as well as extremes. The efficiency of the cast iron heating system and the effect of the portable electric heaters needed to be established and their use restricted if necessary.

Investigation

Wireless temperature and relative humidity sensors were installed around the Hall – near the doors, at each end, in the middle and high up in the roofspace. Data was recorded over a 12 months period before conclusions were drawn up.

An assessment of how often the doors were closed was also made together with discussions with stewarding staff as to how the Hall is used for events.

Action Taken

The use of the portable heaters was reduced as they were found to cause sharp rises in temperature and subsequent falls in relative humidity.

Site staff (both stewards and early morning cleaners) were asked to keep the doors shut until the castle becomes busy in the morning. This gives the building an additional 2 hours in the morning and evening to balance it’s environment before the doors are left open.

Discussions are continuing with engineers as to how to adapt the current heating system to be controlled by a humidistat and thermostat combination.

Outcome

The reduced use of the portable heaters has reduced extremes of temperature and relative humidity. Conditions are being further stabilised at the beginning and the end of the day with the side effect of saving energy.