The growing ambition of sustainable building in Ireland has never been more thoroughly embodied than in the recently completed St Mary’s Credit Union, Navan, Co. Meath.

Central to the building’s design, engineering and construction is an approach that is holistic in the truest sense, driven by architects Gaia Ecotecture’s belief that the building—linked to the original credit union built by the firm in the late 1980s—should act as a living structure; its elements interacting dependant on the needs of the building’s users and the challenges and benefits thrown up by shifting weather conditions and natural resources.

The attention to detail inherent in this holism has created a building that is innovative in so many regards that focusing on any one aspect of the building—such as the fact that this is Ireland’s first 5-storey timber frame building—would do the building as a whole an injustice. In recognition of this fact, the building has been selected amongst a handful of cutting edge projects around the world for presentation at the World Sustainable Building Conference in Tokyo.


Embodied Energy and Lifecycle Analysis

We’re blessed with an excellent client—an articulate and careful management team from the board, to the executive, to the building committee, to the general manager. They had put their trust in us in the late 80s, and we’re very pleased that they came back to us. As an owner-occupier to the building, they were open to the persuasive argument of prolonging life to first replacement, keeping down the use of external energy sources such as grid electricity and gas, and investing in energy producing devices such as double wall and box windows, photovoltaics and solar thermal. The payback period on these devices is fully justified commercially speaking through lifecycle analysis when you have an owner-occupier. A pernicious problem is that developers, who “lash the thing up”, sell it quickly, and turn their money over, couldn’t care less, and the unfortunate tenant is left with low performance fabric, which if they have a repairing lease, rapidly becomes an ‘albatross’ that they have to pay for. We were in the position here that the owner-occupier is responsible for the maintenance costs, and there are excellent studies by our own cost managers Gardiner and Theobold, et al which show that the life cycle running cost of a building greatly exceeds its first capital cost, with conventional building. The cost to the organisation is minimised by intelligent investment in quality.

View of the clay and steel clad south west facade of Navan Credit Union—a high embodied energy cladding specified with durability in Irish weather conditions in mind

The fact that we now apparently need four planets to maintain our profligate life style means that if you’re conscientised about your children or your children’s children, you have got to move towards making buildings on the Factor 10 principle—that we use less of everything, much more efficiently. Factor 10 is by no means out of the question. If you look in ‘Green Design; Sustainable Building for Ireland’ you’ll see that locally produced air dried softwood has embodied energy of about 110, on a scale where aluminium is in the region of 75,600, KwHrs / cubic metre and concrete products based on conventional Ordinary Portland Cement and steel (103,000) are up there in the mega numbers. We’re dealing here with step changes in building culture. If we accept the word of the UN Environmental Programme team in their annually updated GEO 2000 reports we need to change. This Credit Union building goes as far as possible, in a streetwise and alchemically alert way to bring down embodied energy. It’s not fundamentalist—where we need steel we use steel. We’ve used a ‘filigree’ of galvanised steel, with zinc cladding elsewhere in the building with flashings and so forth where it is appropriate. Those relatively small volume materials carry an embodied energy burden, but they’re applied intelligently, to do the task for which they are best suited. The vast bulk and mass of the building is timber, and this timber is in fact protected by the high embodied energy materials on its external face.

5 Storey + Roof Timber Frame

Years of research have gone into this timber structure. We trawled Europe and North America for the most advanced timber technology. We’ve gone to see the leading people in Austria , Germany , Switzerland , and Scandinavia , and to cut a very long story short, Projekt-Holzbau Merkle in South Germany had previously earned their credentials with a colleague of ours in GAIA International, Joachim Eble. With their engineers, Pirmin Jung, we worked through a design process within the terms of Eurocode 5, BS 5268 and the German DIN standards amongst others to develop the design. The key point of the structure over five stories, of course, turns on the connections. The delightful engineering involves tiny amounts of steel used to form the connections, but this steel is totally submerged within timber, so that the timber itself is acting as an insulant to the thermally vulnerable steel, in terms of fire protection. The building is being presented at the Garmisch conference later this year by Pirmin Jung, and there is great interest in the building. We devised the basic structural scheme but great credit must go to Pirmin Jung’s team for detailed analysis and shop drawings.

The lift shaft itself is engineered in timber. There was a proposal to use concrete which we discounted. In other projects where concrete and timber have been used together with less than total success because they are two disparate materials. They behave entirely differently, and if they’re used in conjunction it can cause great problems with settlement, expansion and contraction.

The staircases have been attractively designed to encourage use in lieu of lift for healthy exercise and reduced energy use

The timber engineering aspects need to be treated with great caution. Every building of this kind must be closely engineered. The fire safety aspects, moisture content, density and stress grading required engineering of a very high calibre from Jurg Stauffer of Pirmin Jung’s office, working in close collaboration with the architects. Readers of this article cannot take it that they can, in cavalier fashion, build to five stories. This building is a hybrid between a frame structure and a skin or panellised structure. The wall panels came complete with sealed insulation, preformed windows and so forth to infill around a skeletal frame. It’s a hybrid interaction between frame and skin, rather like the bones, cartilage and ligature of our own bodies. We’re not just skeletons—we work with a tenuity of skin and tissue, and this building is rather similar in its concept to that. An additional key point is racking (lateral) stability and strength. In certain very extreme weather conditions—the ‘Clonee tornado’ or the recent ‘Katrina’ hurricane, are cases in point—there can be negative uplift forces on the substructure. So there are holding down bolts at certain points to literally hold the building onto the substructure. The dead load of course is much lighter than a conventional concrete structure, thereby significantly reducing substructure, which in this case consists of continuous fluidised augered piles.


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