CASE STUDY MARY ROSE MUSEUM
to maintain the museum at a positive pressure. ‘Sensors in the extract duct will monitor humidity levels so that on a rainy day, when visitors enter with wet clothes, we can ramp up both supply and extract rates to capture the moisture at source,’ explains Lloyd. In addition to the fresh air supply, the galleries are fitted with two fan-coil units on each floor to provide additional cooling for peak loads. All the ductwork and headers for the
system are already in place to allow a swift changeover between the drying and final display modes.
Three chillers provide cooling
Ready for its public In 2016, when the timbers are dry, the hot box will be dismantled and the fabric ducts removed, allowing visitors to gaze directly at the hull from the galleries. ‘From an environmental perspective, that means there could be 150 people present at any one time in what is, effectively, a giant display case containing the hull,’ Lloyd explains. The system has been designed to enable
Models of the shear stress (above) and airflow velocity (right) on the inside of the hull
PROJECT TEAM
■Client: The Mary Rose Trust ■Architect: Wilkinson Eyre Architects
■Interior architect: Pringle Brandon Perkins+Will
■Consulting engineer: Ramboll UK
■Cost consultant/CDM Coordinator: Davis Langdon (Aecom)
■ Exhibition design: Land Design ■ Main contractor: Warings
around a primary loop. Two secondary circuits connect to this, one to feed the hull AHUs and the other to feed all other services within the building. To maximise the AHUs’ ability to dehumidify the air, the chilled water is supplied at 2°C (with a 6°C rise); for the chilled water circuit serving the main part of the building, the chilled water is mixed to bring it up to a 6°C supply temperature. However, to save energy the chillers operate at the raised temperature of 6°C when dehumidification loads are minimal. A small AHU located in the first-floor
plant room supplies fresh air for the visitors and pressurises the space. To ensure no more outside air is supplied to the system than is necessary, the AHU has a variable speed fan, with the extract rate balanced
32 CIBSE Journal September 2013
the changeover to be completed swiftly and with minimum disturbance. ‘All the design work has been done so that at the flick of a switch, and by moving a few dampers, the environmental systems will be transformed from hull-drying to hull-display mode,’ says Lloyd. To develop the final display solution, the engineers returned to the digital model of the ship to examine conditions around the hull with the hot box removed. Correct air movement is critical, even when the hull has dried, to maintain stability of the timber. The CFD analysis showed that the best way to avoid areas of stagnant air was to supply conditioned air at a number of levels using directional air-jets. As part of the changeover, the visitor walkways used by the visitors will be fitted with air locks between the galleries and the ship hall. The same three AHUs currently used to dry the hull will be reused to maintain the environment within the ship hall. The units will be configured to run in recirculation mode with two operating and one on standby. When the works are completed, the Mary
Rose hull will be on display a short distance from the mudflats where Tudor craftsmen first assembled the vessel hundreds of years ago. The museum will be a fitting tribute to their work, to the years of careful restoration and to a cleverly designed ventilation system that will enable the hull to be preserved for generations to come. CJ
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