Possible too much filtered sunlight might be an issue. Maybe somebody who has used window screen in the past can chime in.

Kevin

I'm having a hard time picturing this because my broccoli grows so tall, I don't see how a raised bed that has a top wouldn't have a deep enough side to shade it when it is small?

At any rate, if the sizing works well for you, do make sure there are no gaps, and that the moths don't fly in when you have the top open. I have covered my brassicas with netting before, and if there is a tiny gap between sheets of netting, the cabbage worm moths will find it, get inside, not be able to figure out how to get out, and say, "well, while I'm in here, I may as well lay eggs all over this stuff."

I've also sometimes covered brassicas with thin fleece, and the filtered sunlight does make for a later harvest. Not sure if this would be similar to screening or not.

I use row covers with abandon all over the garden for brassicas and as long as you tuck the edges in tightly and weight with rocks, they work great. I've used them for years and years.

We have wanted to do this same thing! We thought of building a walk-in area covered with row cover fabric. Cabbage butterflies are a terrible pest here.

You can throw some nylon tulle on them so the butterflies cannot get in and lay eggs in them For slugs, the tulle has to be secured in the ground, with no open area. I cover some of my small seedlings early on, otherwise slugs can eat them down to bare ground. Nylon netting can also prevent rats, flea beetles and rabbits It is a versatile thing.

Thanks, all. I guess I should add to my post the fact that as my name might suggest... I like to build and create things. I build complex, eccentric, and challenging interior architecture all over the world, mainly for the very wealthy. Sometimes (more often than that!) I get tired of millionaires and just want to make something simple. For me. This "screen room" is perhaps unnecessary effort, but it does bring together 2 of my favorite things: Growing and Building. Anyway. This is probably too much information! The beds I'm planning to cover are in full sun, though i hadn't given thought to the window screen blocking some light. Do any of you feel that the light blocked would have any significant impact... positive or negative? Also, i have it in the back of my head that these hinged frames (basically a 30" tall cage) will provide support for shade cloth to shield some of the cooler temp loving crops from summer heat in hopes of extending their harvest.

The top gardener in our area built a screened covered raised bed for broccoli last season to deter the root maggot flies. It worked great. No problems with root maggots, and the broccoli grew very well. I don't think the screening blocked enough sunlight to be of any concern.