The Lowry – innovative solutions
If you stand on the north end of Pier 8 in Salford Quays you will see what appears to be the prow of a ship surging out of the dockside. This is The Lowry, part of a programme of redevelopment of the previously derelict Quayside area.
This imaginative design, by architect Michael Wilford, houses a multi-purpose centre with galleries for the paintings of L S Lowry and temporary exhibtions, a 1730 seat auditorium, a 466 seat adaptable theatre and an Artworks Gallery – an exciting place intended to encourage interactive play involving the arts.
The initial brief for The Lowry described the project as a waterfront home for art, innovation and entertainment and was seen as part of the overall masterplan of development of Pier 8.
The Lowry's multi functional purpose and its positioning on the canal side have created specific problems. Each key area had to be considered individually and the specific problems addressed before the overall concept could be considered as a whole.
The M&E and structural consulting engineers on the project are Buro Happold based in Leeds and a lot of these problems have fallen into their lap to solve.
An initial problem was the ground water level, which was closely related to the level of the water in the canal, which was only about 1.5m below the starting ground level. This meant there was a significant potential for the building to float and it was necessary to incorporate measures into the design to overcome this tendency. The structure now stands on over 800 piles socketed into the Bunter Sandstone. The basement has had to be waterproofed to grade 4 in accordance with BS 8102, which has involved the use of a double waterproofing system.
It was initially hoped to attain a high Breeam Assessment for the building, but the very design and intended use precluded that. Efforts were still made to make it as energy efficient as possible and to this end canal water was used in the cooling system.
This use of the canal water for cooling proved an interesting exercise. The architects design philosophy for the external appearance of the building prohibited the use of air cooled chillers, so for energy and aesthetic reasons the use of water cooled chillers was seen as an ideal situation.
The canal water has been used to cool the condensers, which must maintain a minimum of 15degrees centigrade to suit the physical properties of the Refrigerant R147a. Analysis of the seasonal variation of the canal water temperature showed it varied between 4 and 24 degrees centigrade throughout the year. The water level was identified as being very reliable; the rise in level caused by a breach of the lock gates below Pier 8 after a collision had only happened once in recent memory and so wasn't considered to be a potential problem. It was felt the silt build up in the canal could have been a problem but it was revealed that a programme of regular dredging was already in place. The canal is 9 metres deep and the silt levels vary from 2.5 to 6 metres in depth. The degree of variation of silt depth had to be taken into account when considering the position of the water intake.
The differing forms of construction of the canal walls further complicated the positioning of the intake pipes. The north side of the Pier 8 had arches and the south side had a flat wall. Initially it had been intended to drill straight through the wall about 1 – 2 metres below the waterline but the technical difficulties and the associated costs were prohibitive. The intake pipes were finally positioned above the waterline although this meant suction lift pumps had to be specified, to draw the water up 2 metres. The pipes being above the water and protruding from the canal wall also meant that fenders had to be installed for public safety.
Water analysis of the canal revealed a high level of contamination existed. For this reason ABS plastic was chosen for the pipework and stainless steel for the plate heat exchangers. The water required filtration to remove particulate material prior to entering the cooling system. Coarse self-cleaning strainers were used which would provide continuous filtration and for reliability, duty and stand-by units were specified.
The team at Buro Happold were satisfied that they had designed a system that overcame the technical difficulties. But then it was announced that Zebra mussels would be introduced as part of the cleaning operation, which created a new set of problems. Zebra mussels are very efficient in cleaning water and, of course, they are environmentally friendly but unfortunately they also have been responsible for millions of dollars worth of damage to cooling systems in America. The problems arise when their larvae attach themselves to the heat exchanger plates and foul them. Research into the Zebra mussel proliferation demonstrated that the system proposed for The Lowry would give good protection against the main threat (of larval attachment on the heat exchange plates). High turbulent velocities provide the greatest degree of protection, and in addition connections on the plate heat exchanger pipework were supplied to facilitate chemical cleaning. One particular chemical 'Endod', a naturally occurring substance from the African Soapberry, is very effective in killing the mussels.
Another brainteaser for the team was the design of the main foyer. This is a fully glazed façade consisting of planar glass, which varies from 11 metres to 16 metres in height. In an ideal world it should be double-glazed but the manufacturers of the double glazed planar glass units advised that panels of that size would require replacement every 4-5 years. This would leave the client with a hefty and unacceptable maintenance bill. The decision to use single glazed units was taken but this left the mechanical engineer the problem of how to prevent condensation.
Initial investigations into the capabilities of fan assisted perimeter heating revealed that they did not have sufficient throw to cover the full height of the glazing, in fact only 2.5 – 3.5 metres would have been covered. It was also impossible to find a route to duct air from the central air-handling unit.
An alternative was to install a trench, large enough to house fan coil units, and although this was an improvement over the fan assisted perimeter heating it still provided inadequate throw. Therefore, air had to be directed towards the glazing from high level, and the use of jet nozzles gave adequate throw.
It was obvious to the design team that the use of warm air to prevent condensation would involve a considerable amount of air and substantial energy costs. The main theatre is adjacent to the foyer, and therefore it was possible to duct the warm air from the theatre into the foyer glazing jet diffusers. The energy required to prevent or clear condensation was thus greatly reduced and this will cut the running costs. The solution seemed simple and fitted in with the policy of energy conservation.
The practice was not quite so easy. Difficulties were experienced with the distribution of ducts from the theatre zone to the foyer roof. These were made even worse when the architect required additional and larger openings between the theatre wall and foyer, which meant the route between the theatre wall and cladding had to be structurally deeper. In effect, the duct zone had been closed off. This was overcome by casting a series of 200mm diameter tubes in the concrete wall to which ducts could be connected at either end.
It was identified early in the design process of the Lyric Theatre, that displacement ventilation would offer the most energy efficient system of handling air movement. The extensive light systems positioned at high level developed in excess of 150kW of heat, which would be better left at that level.
It was necessary to give the client, The Lowry Trust, as much flexibility as possible in the operation of the air handling plant because of the different occupancy patterns likely with this variable use theatre.
It was decided to split the air handling plant into three zones; stalls, 1st tier and 2nd tier, and for further energy efficiency these would have variable speed fans linked to carbon dioxide levels. Air is ducted to plenum zones beneath each level of seats. It is then supplied to the stalls via seat pedestal diffusers and by step diffusers to the 1st and 2nd tiers.
The air handling units for the 1st and 2nd tiers were located adjacent to the theatre on the Northside. The location for the air-handling unit to serve the stalls presented a greater challenge. Initially it was located within the large canopy above the main entrance and ducted down a canopy leg into an underground builder's work duct. Budgetary pressures, however, demanded the canopy structure to become lightweight and unable to support the plant. Another space was located within the plant room above the Hexagon hospitality suite. This route was underground and also provided a route for pipework serving the Hexagon. The exhaust system from the Lyric Theatre consists of a single fan with inverter drive, it's speed linked to the summation of the three supply fans. Air is drawn from the theatre at the rear of the stalls and 1st tier and from high above a perforated ceiling.
The theatre acoustic requirements demanded a NR20 space and all the ventilation systems have primary, secondary and tertiary attenuators as well as some acoustic insulation to prevent sound penetrations from the plant rooms.
The visitors to the centre and the theatregoers enjoying the performances in the Auditoria of The Lowry will be able to sit in comfort in their sumptuous surroundings and enjoy the visual and acoustic experience unaware of their environment. This will be testimony to the skill of the teams involved in the design and construction of the building, making a reality of the architect's vision – and overcoming a few difficulties along the way!
