Homes with green labels in most cases mean energy efficiency, burning less fossil fuels, low-formaldehyde kitchen cabinets, green carpeting, low or VOC-free (volatile organic chemicals) paints and other materials, "green roofing" etc. Most people simply assume that "green" equals "healthy" and never give a second thought to toxicity that might come with their "green home."
It is true that air-tight buildings are energy-efficient but at the same time, the indoor air pollution might be devastating. In other words, proper ventilation is crucial but at the same time pretty much neglected in these new buildings.
All the "green materials", used to build the "green houses" are not necessarily completely nontoxic. At the moment, it is still quite difficult to find out how buyers can tell if a product is both green and healthy but with the rising consciousness, things are moving in the right direction.