Rammed Earth - Nk’Mip Desert Cultural Centre
A sustainable response integrates culture and landscape
View along the rammed earth entry wall, an attractive and durable construction with excellent thermal qualities. Note the section of Cor-ten steel at the location of the service yard.
by HBBH Design Team .The design of Nk’Mip Desert Cultural Centre is a specific and sustainable response to the building’s unique context - the unusual Canadian desert found in the South Okanagan Valley in British Columbia. Sited adjacent to a remnant of the Great Basin Desert, of which 1,600 acres are being preserved by the Osoyoos band as a conservation area, this interpretative centre is part of a larger 200-acre master plan.
The partially submerged, 820 m2 building features exhibits that celebrate the culture and history of the band, and is designed to be an extension of the remarkable site. The desert landscape flows over the building’s green roof, held back by a rammed earth wall. The building is carefully sited to draw the eye away from the encroaching development of Osoyoos to the west, with the height of the wall set to create a layered view of the surrounding desert.
Visitors enter the interpretive centre at the midpoint of a gently arcing concrete wall. Inside, a theatre and “black box” exhibition space present information about the band and its historical relationship with the land, while the round volume of the “pit house” at the centre of the exhibition space invokes the experience of conversation around a fire.
From here, visitors move through a glazed wall into an exterior exhibit space, and the adjacent rattlesnake research facility - part of an award winning conservation project for this endangered species. This area also serves as a trailhead for guided and unguided walks along 50km of paths through the desert.
Most striking of the project’s many green design features is the 80m long, 5.5m high and 600mm thick rammed earth wall. This earth and concrete based wall system combines two -250mm leaves of compacted sand and cement with 100mm of insulation sandwiched between.
The technique results in a physically strong, durable wall with excellent thermal qualities - heating up slowly during the day in the hot Okanagan sun, and releasing its heat in the evening.
The habitable landscaped roof reduces the building’s visual impact on its surroundings, and adds to the area of desert habitat to be re-established on the site. The roof also provides further temperature stabilization and insulation.
Radiant Heating and Cooling
Various heating and cooling options were explored for this arid environment. Our analysis showed that a radiant heating and cooling system incorporated into the ceiling and wall slabs would yield far greater energy savings than traditional air-conditioning while also creating a more comfortable indoor environment.
Unlike conventional HVAC forced air systems, radiant systems use a water-based approach. Tempered water runs through a series of pipes embedded in the ceiling to gently heat or cool the facility using low-intensity radiation. As a thermal conductor, water is 3,000 times more efficient than air - resulting in substantial energy savings, while creating a higher quality indoor environment.
Air Displacement
An outdoor air displacement ventilation system was also installed to complement the radiant heating and cooling system. The underfloor air distribution system supplies 100% fresh outdoor air at the occupant level through floor grilles. The supply air can be introduced at a temperature that is closer to the desired room temperature for substantial energy savings.
The return air located at ceiling level takes advantage of the natural stack effect occurring from hot air buoyancy. The system needs no mechanical fan power and also works to remove indoor pollutants and odours from the space without re-circulating the stale air supply.
Water Conservation
Water is scarce in this region, and supply for the building comes from an on-site well. Demand is reduced by about 40% by incorporating low-flow faucets, waterless urinals, and dual flush toilets.
Blue Stain Cladding
Another feature of the building is the selective use of ‘blue stain’ pine for exterior cladding and soffits, as well as for interior millwork and other finishes. The material is milled from trees that have died prematurely as a result of mountain pine beetle infestation, itself a by-product of global warming that has had a devastating effect on the forests in the interior of BC, including those in the area around Osoyoos.
Although the lumber is not affected structurally, its irregular blue staining has presented marketing difficulties for the industry. Through Canfor we were able to locate a shipment of high grade dimension lumber that had been declined by a Japanese buyer, and secure it for use in the project.
It was felt that the irregular patterning of the stained areas added a layer of visual texture that when repeated was quite beautiful, and the team wanted to utilize the material to demonstrate that its inherent qualities were readily marketable.
The wood used was 38×89mm dimension lumber re-sawn to square the edges to 30×80mm. Exterior wall applications were constructed as wood slats over a plywood sheathed wall assembly. The blue stain pine received a tinted stain/sealer on the exterior and a clear sealer on the interior.
A shift in government policy has lifted restrictions on the types of buildings permitted on reserve land. The Nk’Mip project has benefited, being part of a growing trend that explores the expressive potential of architecture to convey the rich past and the transforming future of aboriginal culture.
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Credits
- Client: Osoyoos Indian Band
- Architect: Hotson Bakker Boniface Haden Architects and Urbanists, Vancouver
- Structural Engineer: Equilibrium Consulting Inc., Vancouver
- Landscape Architect: Phillips Farevaag Smollenberg, Vancouver
- Mechanical Engineer: Cobalt Engineering, Vancouver
- Electrical Engineer: MCL Engineering, Vancouver
- Code Consultant: LMDG Code Consultants, Vancouver
- General Contractor: Greyback Construction, Penticton, BC
- Rammed Earth Wall: Terra Firma, Salt Spring Is., BC
- Photos: Nic Lehoux, Vancouver
Materials
- Cast-in-place concrete construction with a rammed earth feature wall - a mixture of local sand, soil and Portland cement with about 10% water, in two -250mm leaves of rammed earth with 100mm of insulation sandwiched between for an R33 insulation value, wall not sealed; Cor-ten steel at entry to service yard; green roof.
- Bluestain pine dimension lumber 38×89mm re-sawn to 30×80mm to square the edges, applied over wood furring at 550cm o.c. on exterior and interior walls and soffits, finished with a tinted stain/sealer on the exterior and a clear sealer on the interior; also used on the reception desk.
- Radiant heating and cooling system incorporated into the ceiling and wall slabs; low-flow faucets, dual flush toilets, and waterless urinals provide savings of over 40% in potable water consumption.
- Building area: 850 m2
- Cost: $3.5 million