formetoknowandyoutofindout said "I might be interested in your old skylight. Thank you for this info. The skylight that is going to be replaced is 4×4 foot it's still in good shape, bubble style, hard plastic. In my option it's not energy efficient, but if you had a work shop and wanted more light, perfect fit. I'd just give to you. "
There isn't a skylight out there that is energy efficient. In fact, the energy code limits the amount of roof space you can use for skylights for that very reason.