“Ancient buildings were greener than new buildings today,” says John Ochsendorf, adding that buildings in the U.S. now consume 40% of all energy.

Old buildings were built to the natural environment. They took advantage of prevailing winds in summer or natural light in winter. Overhangs were built for shade in hot climates; in cold ones, buildings faced the sun.

“Over the past century, heating and air conditioning became widespread and energy has been relatively cheap, so now, rather than designing a low-energy building at the start, we just correct a poor design by pumping in energy.”

A world expert on ancient buildings and a pioneer in alternative engineering, Ochsendorf is now working to design zero-energy buildings for the world. The winner of a MacArthur “genius” award, and an associate professor of architecture and civil and environmental engineering, he recently partnered with students and local achitects to build an innovative, energy-smart museum in rural South Africa. The result was a lower-cost design and an environmental impact reduced by 80%.

Rather than conventional construction, the team used local materials (mostly soil) and hired local people. They used a 600-year-old vaulting technology, and a quarter of the energy normally used in materials and in the construction process.

By supporting the local economy, Ochsendorf says, side benefits of his method can include reducing poverty in the area and empowering local people with new skills and experience. The building won several international awards, including World Building of the Year at the 2009 World Architecture Festival.

“A good solution solves multiple problems, and lowering energy use in buildings is a win-win. It reduces costs, it pays for itself almost immediately, it reduces environmental impact so it’s better for the planet, and it can lead to healthier communities and healthier people.”

With  an 800-year-old Gothic cathedral in mind, Ochsendorf and his students also helped design an energy-efficient conference center in England near the White Cliffs of Dover. The building uses the medieval technology of masonry vaulting. Compared to a standard glass-box office building, the conference center took 80% less energy to build and now takes 70% less energy to operate.

“When you can develop home-grown technologies with locally available resources and locally available talent, you’re closer to realizing a more sustainable future for that region,” he says.

With funding from Kabcenell Foundation, Ochsendorf recently rounded up a team of students to build latrines at schools in Cambodia. They reduced the cost of construction and increased the use of local materials, this time by using agricultural waste — the ash from rice husk — to create concrete.

“Our fundamental challenge is to rethink how we use and consume our resources, how we meet our needs and live the affluent lifestyles we’re used to while dealing with climate change.”

A housemaster at an MIT graduate dorm, where he lives with his wife and two children, Ochsendorf is installing light sensors, using low-energy light bulbs, and posting signs on elevators marked: “Take the stairs.” “By making occupants aware, we’re moving towards smarter buildings,” he says.

“Thirty years ago, nobody was asking for zero-energy houses. It just wasn’t on the radar. Today, people want to live in homes that use dramatically less energy for economic, security, and environmental reasons.

“In 50 years, I’d love to see us living in more intelligent buildings, buildings that can adapt to outside climate, healthier buildings that bring in fresh air and more light. I’d like to see us create a new generation of creative engineers and architects, who are thinking in highly creative ways backed up by rigorous analysis, and showing that zero-energy buildings are possible — because that’s where we’re headed.”