Hello, love your post, and cold frame. Thanks for posting. .
I live in zone 6b, I hybridize daylilies for a hobby. I also use a cold frame a lot like yours. Will try to post some pictures. .
My cold frame is constructed of, wood frame, single wall polycarbonate panels all the way around the frame and lid. For ventilation I have a house foundation vent ( 8 × 16 ) that is heat activated ( totally open at 70 degrees, closed at 40. ).
In our coldest months ( Jan. Feb. ) I staple large bubble, bubble wrap to the inside frame,for added protection. Have thought about the light bulb, but have not tried it yet.
Daylily seeds are started in sept., planted out in seedling beds in May.
Like a lot of your ideas,will be trying some although daylilies are different a cold frame works great for a lot of plants. Thanks again for your post.

Thanks Kennysh.
I like your idea of using polycarbonate panels....I may replace my front wall with polycarbonate for more sunlight transmission. Your auto lid opener is also a great idea. I would love to have an automatic opening system, but my lid is heavy glass. So manual opening, it is for now.

I did add two 3ft grow lights to the interior for those days when the outside air is too cold to open the cold frame and when I leave the protective coverings in place.

Great looking group of day lilies! How many varieties do you grow?

We ate our first lettuce and radish leaves last night - gathered a small amount of outer leaves. They were tender and delicious. Garden fresh home grown greens in the middle of Feb makes this project worth doing.

I'll add pictures here of the growing greenies as they fill the cold frame.

Thank you both for your wonderful cold frame ideas. I'm been thinking about making a cold frame here in 7a, which is not too much different from 6a, though we have fewer day/nights of below freezing temperatures. The added bonus for me is that I can use the idea to keep the rabbits and deer out if I put a floating row cover on once temperatures have warmed up. If it happens this year, I'll post some pictures. Hurrah to both of you!

Jewlgurl, those fresh greens sound good 👍.
No automatic opener , that black rectangle is an automatic house foundation vent, works great. Still have to prop open top when days start getting fairly warm. The vents come in a couple of different sizes ( most home improvement stores.) I think under 20 dollars.
I have 200 named varieties, and approx 800 seedling, counting the 250 you see in the coldframe.
Meggosmith, . You will enjoy a coldframe very much. Do your research, their are a lot of options out there. :thumbsup:. If done correctly they will last a long time.