Article: Some of the cleaner energy facilities in Boston include the Allston green district, with three ecologically compatible housing facilities. Boston is also breaking ground on multiple green affordable housing facilities to help reduce the carbon footprint of the city while simultaneously making these initiatives financially available to a greater population. Boston's climate plan is updated every three years and was most recently modified in 2013. This legislature includes the Building Energy Reporting and Disclosure Ordinance, which requires the city's larger buildings to disclose their yearly energy and water use statistics and partake in an energy assessment every five years. These statistics are made public by the city, thereby increasing incentives for buildings to be more environmentally conscious.

Now answer this question: How many green housing facilities does the Allston green District contain?
three