There are many sources of greenhouse vent motors/fans on line. If you have the exact dimensions of your current vent opening (and/or can make some small changes in the supports) , and know CFM of the fan to be replaced, you can fairly easily replace the old ones with new. A little work on the attachments and openings of the new units to your structure should not be a problem, having done two such replacements in my greenhouse.

It's somewhat unavoidable that a greenhouse is going to get hot in the summer. But in a place like the PNW it's totally manageable with three things: - air movement through vents, windows, and doors - aided by fans - shade cloth during the hot parts of the summer - a misting system, which is pretty easy to make. I don't think one can create a non-hot greenhouse without those components. So I would add that to your design considerations. Basically the more solar gain you add, the more cooling measures you'll have to take. A glass roof seems like asking for trouble, with hail, falling branches and other hazards. If you want a clearer material than fiberglass I'd go with twinwall polycarbonate. I would go for glazing on the east and west sides for sure - then add shade cloth if needed. Oh, and if you don't have it already, a book called the Greenhouse Gardener's Companion by Shane Smith (I think) is a must. Happy planning!

This one has been replaced with Ortho's 'All about Greenhouses' so it's marked down. Greenhouses Planning, installing & using greenhouses. by Ortho http://www.alibris.com/search/detail.cfm?chunk=25&mtype=&qtit=greenhouses%20planning%20%20installing%20and%20using%20greenhouses&S=R&bid=8270618225&pbest=&pqtynew=&page=1&matches=1&qsort=r So has this one. How to use and build a greenhouse by Ortho http://www.alibris.com/search/detail.cfm?chunk=25&mtype=&qisbn=0917102746&S=R&bid=1515624663&pbest=&pqtynew=&page=1&matches=29&qsort=p Here's the newest version. All about Greenhouses by Ortho http://www.amazon.com/gp/reader/0897214633/ref=sib_dp_pt/102-5793094-7483340#reader-link This one also seems to be out of print. But found it also. Really a wonderful book. Greenhouses A Sunset Book. http://www.alibris.com/search/detail.cfm?chunk=25&mtype=&qtit=sunset%20greenhouses&S=R&bid=8241610148&pbest=&pqtynew=&page=1&matches=1&qsort=r I have them all and find the all very valuable. Even though the first two are out of date and was replaced they are different with different plans. So you can get the three for the price of one. The alibris site might have the newest one also. I didn't check. Sorry I don't know how to post the link in the message.

i am selling all of the glass from my lord and burnham 14x25 evenspan greenhouse i am asking 1200.00 if anybody is interested email me thank you...