Looking for innovation in building materials and using existing research into passive building design, we identified a product called Hemcrete® developed by UK company; Lime Technology. The Lime Technology team brought onboard professional design and modeling from Emission Zero A&E and Emission Zero R&D, and a back-to-basics approach to a new storage facility was instigated. By using the thermal efficiency and hygroscopic performance of Hemcrete® (a low embodied energy material comprised of Lime and Hemp cast in prefabricated panels), the team produced a robust design for a 1000m2 three-story, 6-room facility to house collections of horse-drawn carriages, fine art works, wooden ship models and paper archives from the railway industry. This new facility was to be constructed within an existing unheated aircraft hangar that provided an additional layer of protection from the elements. These particular collections required stable humidity and temperatures to protect against damage, where conditions within the hangars broadly follow the external environment, the parameters for the design were set at 16-19⁰C and 45-55% RH +/- 5% mirroring existing guidance.
Traditionally mechanical & electrical air-conditioning is used to achieve these parameters; however it was believed that the active properties of Hemcrete® would be able to meet our needs with limited &E intervention. The characteristics of the Hemcrete® were modeled, and the building designed to create large internal surface areas within the structure so that the hemp could passively buffer humidity changes by absorbing or releasing moisture into/from the walls, controlled by heating and cooling though the air-source heat exchangers, while providing the required insulation to slow temperature changes. Pre-cast panels of Hemcrete® were hung within a steel frame and clad with fibreboard covered with wire mesh (as rodent protection) on the exterior. The internal finish was deliberately left in its raw state, using a permeable magnesium-silicate board, to enable the greatest possible opportunity to absorb/release moisture. A small air-handling system circulates cool nighttime air (or provides warm air if an increase in temp is needed) allows for energy-efficient management of the ambient environment. Electricity consumption was modeled at 28 kWh/m2/yr and is to be supplied by a PV array.
The results Humidity and temperature ranges remain within tolerance at approximately 53%RH and 15⁰C and this provides good conditions for the objects stored there. Electrical consumption is below expectations, with the consumption currently at 20,397.5kW against a predicted 21,000kW – this should continue to fall as conditions within the building stabilise. Combined with the solar array the building should be carbon neutral in electricity use.
By being creative with the design brief, straying outside conventional building products and using a small, knowledgeable, specialist team which designed the building based on sound engineering, the function of the building and the long term operational costs have been minimised. Ensuring that the internal project board had the right resources and the training required to understand performance characteristics of building materials ensured success. By championing new technology and working with architects and engineers we designed out the energy loads usually associated with this sector. The beneficial impacts on the Science Museum’s operations are significant, with reduced running costs and more stable environments for collections. The benefits to other museums within our sector could be significant. Museums are traditionally, and understandably, cautious in their approach to projects, taking on changes only when proven and well understood, but with increased pressures on budgets and resources new ways of working are needed to ensure the long term survival of collections. By taking the leap, championing good careful design and ensuring the aims are well understood by the project team from the outset a successful outcome is assured and can be replicated by others.
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