I have used the window with a plastic bag for several years.
The window makes it easy to see when germination occurs and see the sprouts growing. The plastic bags I use are freezer bags and last for years with only a few each year splitting and needing to be recycled.

In my area the plastic jugs become brittle from sun exposure after 2-3 years. In the 2nd year I have started cutting the top off to remove seedlings and recycling the jugs.

I also use 2L bottles cut in half with the top pushed over the bottom. So far none of the 2L bottles have gotten brittle and have been used for up to 5 years.

In this photo there is one in the back row which still has the bag over it. The other bags have been removed and most of the open windows of the front row have been turned towards the 2L to keep out chipmunks and squirrels.

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