The coldframe house is strong, but not impervious to chill. We had a night of frost, and I thought everything in there was okay. But I lost most of my basil seedlings- only the biggest one survived it. And my one little sage plant almost died (its first true leaves are just big enough to touch them and receive scent of the herb). I rushed it back indoors and propped its stem gently with a nudge of soil- it seems to be recovering. So now I am still shuffling the more tender seedlings indoors on colder nights.