sentence: Built from recyclable or recycled materials , the exterior surface of these houses should be ready to be lit by daylight on sunny days , not to mention skylights and solar panels on the roofs , which are more and more popular , even these days .
modified: Built with recyclable or recycled materials , the exterior surface of these houses should be ready to be lit by daylight on sunny days , not to mention skylights and solar panels on the roofs , which is more and more popular even these days .
transformation: PREP, VERB:SVA, PUNCT