With its roots in medieval England, the Parish Church of St Giles, Cripplegate, has stood the test of time. Now nestling in the heart of the Barbican Centre on the edge of the City of London, it serves both its local congregation and a wider community, with its renowned organ school and recording facilities frequently used by the BBC.
The building was damaged during the blitz, and part of its post-war restoration was to install a new heating system. The underfloor system served the church for over 50 years; however, in recent years it became clear it was failing with, ever more leaks in the floor.
The Parochial Church Council decided that a completely new system needed to be installed and instructed Peter Graham and Associates to draft proposals.
The new system utilises a 145kW biomass boiler from Broag-Remeha, fuelled by wood pellets. Environmentally sound and economically viable, biomass pellets have an estimated carbon footprint saving of 75% over that of natural gas.
The new scheme employs banked radiators in trenches that are set around the perimeter of the nave and in the tower floor. Developed and refined by Peter Graham, the design provides for minimal intrusion into the area of the nave while strictly limiting the buoyancy of the warmed air rising from them, ensuring that the warmed air remains at low level where it is wanted, rather than heating just the roof.
The vestry and another small area are separately controlled, both for timing and with their own compensators. The nave also has a night setback facility for use in cold weather to prevent it becoming too cold at night.
There is a gas boiler option to serve when just the small areas are called, although the biomass boiler serves the complete installation when the nave is in use.
The fully-automatic biomass boiler has been installed in an existing crypt beneath the nave, in a completely closed space, together with the pellet fuel store. Fuel is delivered by road tanker and pumped by air suspension into the bunker.
The air for combustion, plant room ventilation and exhaust gas dilution is mechanically supplied by a variable-speed fan set drawing air from the roof. The exhaust products are diluted to reduce their temperature to 60C to control buoyancy and then, again with speed variation, fan assisted to their exit point, also on the roof.
The church is a listed building and although the installation presented many mechanical and administrative problems during execution, including accidentally cutting a radiator trench into an unknown ancient crypt, they were all ably overcome by the contractor Arnica Mechanical Services Ltd, who completed the heating works in their entirety. That included all the electrical control panels and wiring and lifting the 2½-tonne boiler into the crypt.
Arnica has been involved in many medium to large remedial and replacement boiler rooms and heating systems throughout London and the Southern Counties. The company was able to provide a complete service to the church, from initial reviews to final commissioning.
Arnica also provides on-going service and maintenance for both their own installations and those of others, including 24-hour cover. The contractors commented on the high standard, quality and appearance of the Broag-Remeha biomass boiler, its low carbon footprint and its remarkably good control system.
The outcome has been very satisfactory, being the first biomass boiler to be installed in a City of London church. Peter Graham and Associates have extensive experience of heating installations within ecclesiastical and listed buildings, especially in overcoming peculiar and difficult installation problems, and in working with both the authorities and specialist contractors to achieve targets that some may have thought impossible.