Weald and Downland Open Air Museum

The museum’s former director, Richard Harris, designed the Weald and Downland Open Air Museum building to be energy efficient and contemporary in its design, yet fitting with the aesthetics of the surrounding historic exhibit buildings, including 13th-19th century houses and working buildings.

The museum exhibits the transformation of English building design and technology throughout the ages, displaying over 50 historic buildings which have been rescued from southeast England and rebuilt on the site. In order to blend in with such structures, the new crafts gallery building has a predominantly timber structure, incorporating the NBT’s Natureplus certified woodfibre insulation systems. The locally sourced douglas fir timber frame was constructed by Greenman Carpentry Co Ltd, and is finished externally with fresh sawn larch cladding.


NBT Pavaflex woodfibre insulation was used as infill insulation between the studs of the external walls. OSB was fixed to the internal face of the studs to provide racking strength and airtightness. The external face of the studs is enclosed with NBT Siga Majpell membrane and Wigluv tape, which provide full protection from moisture ingress while minimising air leakage through the building envelope. The tape and membrane are fully age-tested and maintain performance for over 60 years. Batons were then fixed horizontally across the studs with fresh sawn larch cladding nailed to the batons as the external wall finish.

NBT’s Pavaroof woodfibre insulation system was used to insulate the building’s roof. This features NBT Pavatherm Plus fixed in a continuous layer over the rafters, with NBT Pavaflex infill insulation between them. The roof was then finished externally with traditional pan tiles.

Through the creation of a thermal shell, NBT’s woodfibre insulation systems deliver a thermally coherent structure, which, combined with their excellent thermal properties, provide outstanding thermal insulation.

Furthermore, the hygroscopic properties of the woodfibre material makes it fully breathable, meaning that its use reduces the risk of interstitial condensation, resultant mould formation and the associated health risks to occupants and structural risks to the frame.

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