Three brothers originally from Havertown have set out to create affordable buildings that generate their own energy and leave no carbon footprint, writes Russell Gold for The Wall Street Journal.

Tim, Patrick and John are three principals at Onion Flats, LLC, a Philadelphia-based real estate development/design/build firm.

Their latest project is Front Flats, a four-story 28-unit apartment building in Philadelphia that generates as much energy as it uses.

The airtight building is wrapped by 492 translucent, double-sided solar panels and is “extraordinarily energy efficient,” say Tim McDonald and Onion Flats Chief Financial Officer Howard Steinberg.

A one-bedroom apartment there costs under $1,400 a month, less than the $1,750 average people are paying in the neighborhood, according to the rental-listings website Zumper.

“As an architect, if I’m not designing buildings that contribute no carbon to the environment then I’m being totally irresponsible,” says 56-year-old Tim McDonald.

Buildings contribute 38% of global greenhouse-gas emissions, including heating, cooling and construction materials, according to the International Energy Agency.

Onion Flats hopes to show that zero carbon emissions can be done affordably with a powerful combination of renewable energy and energy efficiency.

Read more about this zero emission architectural work at The Wall Street Journal.