glass in
To surround or encircle something with glass. A noun or pronoun can be used between "glass" and "in." I think the architect plans to glass in the atrium.
glass something in
to enclose something, such as a porch, in glass. I want to glass this porch in, so we can use it in the winter. We glassed in our porch last year.
glass in
v. To surround or enclose something with glass: We glassed in the side porch to keep it warmer in winter.