The Building Conservation Directory 2022

16 T H E B U I L D I N G C O N S E R VAT I O N D I R E C T O R Y 2 0 2 2 C AT H E D R A L C O MM U N I C AT I O N S in ventilation for historic auditoria is the use of heat exchange units that use the warmth of the air extracted from the space to heat incoming air from outside so that not all the energy in the heated air is lost. HEATING Large auditoria today are typically heated by burning vast quantities of gas, which is clearly incompatible with a move towards zero carbon emissions. Although hydrogen boilers may be an option in the long term, in the short term often the only viable greener energy option is to replace gas boilers with electric heat pumps. Heat pumps work like a fridge in reverse, extracting warmth from air outside or in the ground to transfer to the interior. In order to meet contemporary expectations of comfort, historic theatres are often heated or cooled to a uniform temperature throughout the year. When first built, much wider ranges of temperature were expected by theatre going audiences. The Globe theatre is by its very nature green, located in a city centre site with very few members of the audience arriving by car, built from timber and requiring no ventilation or heating. Clearly this example has limited relevance for indoor theatres, but should all venues aim for an ambient temperature of 21°C regardless of whether it is winter or summer? Should a theatre consider closing in mid-summer when audience numbers are lower rather than install a new cooling system? DESIGN ISSUES Theatres and large venues can be good places for producing green energy. Large auditoria have roofs often not visible from the street that can be ideal candidates for the location of solar cells, which produce a significant proportion of the energy consumed in a building’s services. This technology is as appropriate for a historic building as it is for a new building. Given that the embodied energy of construction can often be the largest carbon impact of any new work, it is very important to assess the carbon footprint of materials and processes to be used in any renovation. The benefit of using grown materials such as timber is not only that they require lower amounts of energy to prepare, but they provide a way to store carbon extracted from the atmosphere. To put it another way; building with carbon is better than burning it. Clearly it is not always possible to repair or alter historic masonry structures using timber, but care is still needed in sourcing local masonry products so that the energy used in their making is not added to by the energy used in their transportation. FIRST STEPS In the face of such a holistic and detailed problem as climate change there is clearly a danger of inaction, or progress held back by poor understanding of all the issues at play. But in reality there is nothing wrong in starting with easy improvements. Easy wins are by their nature cost effective; it is often the more difficult to achieve solutions that are the most expensive and marginal in benefit. Managers and technicians of historic theatres are well placed to make decisions on where to begin and will know where waste and inefficiencies lie because they know their buildings intimately. Sensible improvements can be made with a combination of planning and pragmatism. An intelligent renovation of a historic theatre will start by understanding the design of the building as originally conceived and whether existing systems can be used or adapted, rather than treating an auditorium as a sealed box to be serviced with new equipment. Every historic theatre should undertake careful planning, with suitably experienced consultants, so that there is an overall plan to work to, but the staff who best know the building will often be best placed to make change, starting with the most obvious gains. The climate emergency clearly affects all areas of life in complex ways that are difficult to assess, but given the energy emitted by historic buildings is such a large and clear component of current carbon emissions, inaction is not a good option. EDMUNDWILSON is a partner of Foster Wilson Size (fosterwilsonsize.com) , an architectural practice with an international reputation for the design of cultural buildings and creative spaces. He is a design fellow at Cambridge University and a RIBA accredited Conservation Architect. A low-energy, low-heat LED lighting scheme at the Hammersmith Eventim Apollo (Photo Tom Cronin)