HEALTHY BUILDINGS: People think they're healthier and more productive after moving their office space into "green" buildings, according to a recent study published on the American Journal of Public Health's website.

A group of researchers working with Michigan State University surveyed two groups of employees before and after moving from conventional office buildings to LEED-certified buildings in the same Michigan area. After moving to the new building, employees said they thought they called out sick less and were more productive.

LEED certification is a Leadership in Energy and Environmental Design ratings system issued by a building industry association. It is the dominant "green" programme for buildings in the US.

The authors estimated a small benefit to employees suffering from asthma and respiratory allergies. Those people would gain 1.75 more work hours per year working in the new building because they would take less sick time.

The biggest boost comes in perceived productivity. The study's authors extrapolated that employees could each work about 39 more hours a year in the new building because of different working conditions such as better light, air quality and ventilation.

To be sure, the survey did not independently track whether employees actually did stay out sick more often after moving to the new building. The authors also noted that the surveys were taken at different times of the year, so seasonal factors may have affected how often employees thought they got sick.

The two surveys tracked 263 employees in Lansing, Michigan.