What a great use of old windows - here in the valley set these up North to South to take the most advantage of the winter orientation. As shown - leave the ends open for necessary air circulation to avoid problems known as "sick greenhouse" where no air circulation and unlimited heat and humidity create the perfect environment for bugs, mold and mildew.
(Pretty, sort of antique looking--and with all our old windows could build alng the baack south crawl space wall--its about 4-5 feet tall!) Green Greenhouse-A smart little greenhouse made from old windows are easily set up to house wall. Here seedlings grow large before they are planted out. Old windows and doors are found at flea markets and recycling stations