The experimental modular home incrementally built between 2013 and 2015 is the basis for the Eco-Building Toolkit. (Photo courtesy Open Building Institute)

The experimental modular home incrementally built between 2013 and 2015 is the basis for the Eco-Building Toolkit. (Photo courtesy Open Building Institute)

The experimental modular home incrementally built between 2013 and 2015 is the basis for the Eco-Building Toolkit. (Photo courtesy Open Building Institute)