Most houses in Latin America are built out of concrete block, and with good reason. It's good quality—in most places—and it holds up well in earthquakes and hurricanes. But there are drawbacks: It's heavy, and it requires a high skill level. Plus, cement can be expensive and hard to come by. (Sound familiar?)
In the mid-1990s, with repeated damage to buildings from hurricanes and facing an economic crisis that reduced the production of ordinary Portland cement, Cuban building scientists at Centro de Investigacion y Desarrollo de Estructuras y Materiales (CIDEM) began looking for an alternative material that could be produced locally to eliminate the high cost of shipping to the island.
Working with the Cuban National Housing Institute; a nongovernmental Swiss agency that provides technical and administrative support; and several other financial and political partners, CIDEM developed an alternative cement that uses recycled waste from the sugar cane industry as a raw material. The material can replace up to 40 percent of the ordinary Portland cement in hollow concrete blocks without affecting quality.
In a pilot program, four local workshops produce the alternative cement, blocks, and tiles and sell the products to local residents, who have used them to repair and maintain their homes. (The program focuses on rebuilding homes in areas heavily affected by hurricanes.) As a result, more than 1,200 families have been able to rebuild, and a potentially hazardous agricultural waste product has been put to good use.
In Central America, Habitat for Humanity International also has found success in post-hurricane construction. After Hurricane Mitch left more than 3 million people in El Salvador, Guatemala, Honduras, and Nicaragua homeless or severely affected in 1998, builders looked for a way to construct sturdy housing quickly. Habitat for Humanity affiliates in Central America have experimented with two building systems—Covintec and Habicon—that offer lightweight, affordable, and aesthetically appealing alternatives to concrete block.
While neither system will be cost-effective for Habitat because the organization doesn't build enough houses to get the necessary economy of scale to make the materials affordable, they're excellent options for standard for-profit builders, says Minor Rodriguez, housing specialist for Habitat in Central America and Mexico. Both have strong seismic qualities and durability and work well in highly humid climates. Plus, with the proper training, the systems are easy to install.
Covintec is a building system that replaces traditional block, column, and beam construction. It comes in 4-foot-by-8-foot panels of tridimensional steel wire that surrounds expanded polystyrene, which is then covered with traditional plaster. Benefits include structural resistance to hurricane-force winds and earthquake activity; quick installation; great versatility (the panels can be used in a wide array of architectural styles); transportation cost savings because it weighs less than block; improved insulation that reduces noise from outside and between rooms; and protection from humidity damage. Plus, Covintec is relatively seismic-proof, and with eight times the thermal insulation of traditional block systems, tests have shown that it provides electric energy savings for homeowners of 23 percent to 27 percent. And because there's no wood and the panels are embedded with steel, bugs and critters can't eat it or chew through it to live inside.
“Covintec panels are very light and much easier to use in construction [than concrete block],” Rodriguez says. “It has flexibility, it's very sturdy, and very strong. I like it seismically very much because it's lighter.
“If you have volume and can organize, it's a good prefab system,” he says. “From 50 houses on, you can do a good and quick job.”
Habicon is a prefabricated construction system developed by the Costa Rican Building Research Center at the Technological Institute of Costa Rica. It was designed to be environmentally friendly as well as affordable; posts and beams use locally available wood instead of imported wood, and the pre-fabrication process reduces waste that would end up in landfills. While it's currently being used in low-cost housing, it's also been used successfully in more-upscale housing there.
Habitat has used the Habicon system on stilt houses, which work well for varying topography; they reduce humidity by keeping the floor off the ground and produce cooler interior temperatures, Rodriguez says.
The earthquake- and hurricane-resistant system is lightweight, modular, flexible, and low-cost, according to a paper written by wood technology engineer Sonia Vargas Calderon of the Costa Rican Building Research Institute. She describes “a main wooden structure formed by frames of wooden post and beams assembled together with metal connectors, on top of concrete piles or bases, or above a conventional floor slab. The structure is covered on the outside by very dense prefabricated reinforced micro-concrete panels, 33 millimeters thick, ... that are used for walls and floor slabs. Panels are stapled to the wooden structure. The gaps between panels are covered with a fine mesh and plastered with mortar on site.”
The wood comes from local plantations, which reduces costs, and is pretreated against disease and insect infestation. The micro-concrete panels and roof tiles can be produced on site, as can the metal connectors used to secure the wooden frames, reducing transportation costs. Easy and quick to assemble by basic laborers (as opposed to craftsmen), the panels have an aesthetically appealing appearance. Doors, windows, closets, the roof structure, and other components can be industrially prefabricated, achieving high quality, minimum waste, and economies of scale.