Reply to LN
Sorry to hear you do not like spiders. The only way to keep them out of the greenhouse is to seal it hermetically. This will do nothing for what you are growing in there. You could try putting net screens over the windows and vents, but I suspect they will still crawl in under the door. Spiders do no harm in the garden or to you. You can get battery-powered suck-up-and-hold spider removers; like a mini-vacuum cleaner but you release them unharmed out doors. If you can get over your phobia enough to get close, then a glass tumbler and index card plop-over and scoop-up method is easiest. You do not have to pick up spiders in bare or gloved hand. The best way to get rid of a fear of anything is to study them. Buy a book on spiders, learn all about their web-building and other habits, watch them, from afar, then closer as they build their aerial silk snares. When you first get into the greenhouse, actively look for and find them, then they will not startle you when you suddenly notice them out of the corner of your eye. Good luck.