5.1 Habitability Improvement in Colombia: Significant Benefits to Homeowners at Minimal Environmental Cost

Program Details

Build Change’s work in Colombia began in 2013. It was our first program to full focus on disaster prevention, rather than also including post-disaster reconstruction. Over the last decade, Build Change has carried out a wide variety of projects in the country, working with homeowners, and local and national governments. One of our more recent programs is in Bogota, with the local government and its Plan Terrazas program, which provides subsidies to households for housing improvements,^[1] including:

• Disaster mitigation measures: Preventative strengthening of the main structural elements of the house to increase resistance against future earthquakes. For example, by adding new ring beams above all walls, and adding reinforced concrete confining columns at wall intersections and window and door openings.

• Structural condition repairs: Repair of damaged elements, such as reinforced concrete roof slabs that are cracked or replacing masonry walls that are unfinished or damaged.

• Habitability improvements: Measures to improve the well-being and quality of life of the inhabitants, such as adding new windows for natural light and ventilation, ensuring the roof is watertight, and providing additional security measures on exterior doors and windows.

• Vertical expansion: The first floor of the house is strengthened to safely accommodate a new second story. If the existing house has a lightweight roof, this is replaced with a reinforced concrete slab. A new second story is added.

The vast majority of informal housing in Bogota follows a very similar design and construction style. Homes are built incrementally, with fired clay perforated blocks and reinforced concrete. Initially, the houses are single-story with a lightweight roof (pitched metal sheets, supported by timber or steel framing), and the brick walls may be unreinforced or confined masonry.

Once the homeowner can afford to expand, they will change the roof to a reinforced concrete slab and add a second story, again using fired clay bricks for the walls, possibly confined by reinforced concrete elements. If funds allow, this process of vertical expansion often continues for several more stories.

The Plan Terrazas program is exclusively for single-story homes. The program concept is to strengthen the existing first floor to resist loads from earthquakes and vertical expansion, and to build a new second floor. If the existing house does not have a slab roof already, the lightweight roof is converted to a slab. The final, two-story building has a lightweight roof.

Findings

Overall, home improvements in Bogota save 51 percent of the emissions of equivalent new construction. On average, strengthening existing homes in Colombia for disaster mitigation, repair, habitability, and vertical expansion saves 9.8 metric tons of carbon dioxide per house 0.09 tons per square meter).

Habitability improvements are often the most desirable for homeowners, and account for just 7 percent of the total embodied carbon. Habitability improvements are often an essential incentive for homeowners to make disaster mitigation upgrades. Simple improvements, such as a new, secure door or paint for the walls are much more tangible outcomes than reduced earthquake risk and can make a positive difference to homeowners’ everyday lives. As these habitability improvements contribute very little to the total embodied carbon of the home improvement intervention, they should continue to be used as incentives to increase wide-scale adoption of home improvement programs.