The recently opened Australian Grains Genebank stores 200,000 seed strains in a hermetically sealed freezer room – and the ultimate thermal protection comes from one of the world's oldest building materials: timber.

The freezer room itself is "just like a big Esky", Mr O'Dwyer said – an insulated metal box at the core of the facility.

That in turn is protected by a metal shed, set away from the metal box, with a gap you can walk along. "That gap is important ... that effectively gives you another layer of insulation," he said.

Timber provides a third layer, acting as a rain and shade screen outside the metal box to protect it from the heat. The timber acts like an external skin.

"Timber itself likes to expand and contract; it thinks it's still on the tree," Mr O'Dwyer said.

The screen comprises independent pieces of timber with gaps in between, allowing the expansion and contraction, and acts as a passive thermal buffer – the heat exits at the top and sides.

H2o chose Canadian western red cedar because it performs well in terms of expansion and contraction. Also, it does not split.

Another advantage is that it does not bleed, causing a brown stain, as many timbers do when they weather. Natural greying was part of the design.

The building, measuring 80 metres by 60 metres, blends into the landscape like a woolshed.

On its western face, a window cuts into the building, giving workers a view of the nearby Mount Arapiles. The window is triple-glazed and can be screened with an external blind.

Timber – spotted gum – was also used for the flooring.

"Spotted gum does not have that issue of expanding and contracting, knotting and the like," Mr O'Dwyer said.

The space is edged with plywood and solid Tasmanian oak stained in the colours of the flora of the Grampians and the Wimmera – "mauves and lilacs".

To get away from the "freezing, white look" of a laboratory, H2o coated the internal spaces of the freezer area and drying room in a coffee brown, inspired by the rusty dock weed in the surrounding fields.