If they are glass we can clean them, but will need to use your windex and paper towels. It would just be labor. Half hour and up. We are not set up for window washing, and we do not get the skylights dirty with our treatment. We treat close to the roof to avoid overspray and it gets more treatment onto the roof and less into the air. We do clean glass skylights, but we do not touch plastic skylights. Also, we need to use the customers supplies and just charge for labor only. We do not stock window cleaning supplies in the van as we specialize completely on roof care.