The goal of this design is the create a simple cabin that lives up to the most ethical building standards I am aware of while fitting into the design targets and constraints outlined by the competition. Those standards are:
4. Energy efficiency
5. Regional and sustainable sourcing
7. Repairability, and
The design accomplishes that by proposing a bomb-proof structure, a simple, two-bent timber frame built upon a solid rubble trench foundation. The timber frame sits upon an insulated grade beam (reinforced perlite-limecrete), which, in turn is filled with loose fill perlite (as insulation) and a limecrete slab to create the building's floor. The walls are in-filled with hempcrete (hemp-lime masonry), which is has a lime-sand render on the exterior and an earthen plaster on the interior.
The roof is insulated with blown-in cellulose insulation, and roofed with cedar shingles. The eastern and western windows, as well as the door, are salvaged. The southern window is a site-built sash with double-paned glazing, sized to provide maximum solar gain for the wintertime. The roof's overhang is sized to provide total shade for that window during the summer months. The entire building is has incredible thermal mass, to stabilize the temperatures during both the summer and wintertimes.
It is important to build naturally to avoid investing in industrial and petroleum-intensive building materials. A truly natural building can be easily recycled or returned to the earth when its function has run its course. Hempcrete was chosen because it seems to be the best option for natural building currently available to us.
Its features include:
1. Incredible thermal efficiency, both in terms of thermal resistance ("R-value") and thermal mass.
2. A very long lifespan due to lime binder (for example, cracks due to movement in the structure actually self-heal!).
3. Zero-toxicity; lime is a breathable material, letting the humidity of the building pass and thereby stabilizing excess moisture. As well, hempcrete is mould-resistant and contains no VOCs or other toxins.
4. Potentially carbon-negative: lime kilns burn at a much lower temperature than cement kilns and therefore uses less energy to produce. As lime sets it absorbs the carbon expelled during firing and returns to limestone over its 1000 year life cycle. As well, the use of hemp sequesters carbon for the lifespan of the building.
5. Easy to build; no specialized trade skills are necessary to master this material. The design is regionally responsive as well as it reflects traditional building methods native to our region and heritage and sources many of its materials from the region. Timbers can be sources nearby or harvested from the property. The lime is sourced from nearby Havelock, NB. The finishes comes from Fredericton. The glazing comes from Amherst, NS.
Perhaps most importantly, this building design leans heavily on the craftsmanship of its builders. If they felt inclined, the builders could saw their own timbers and salvage as many materials as possible. Much creative input is left for them to enjoy - for them to respond to the materials directly. Good buildings are about good building.
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