Coldframe greenhouses are predominantly used for aclimitizing young plants from a greenhouse enviroment along with the increase temperatures to adjust to life in the garden. Coldframes are the middle man were the temperature can be slowly decreased by opening the transparent lids on top through the day and eventually the evening. hardening of young plants is essential to prevent new plants perishing. Coldframe greenhouses can also be used for seedlings to increase there size before hardening them off to be planted outside. See the different coldframe greenhouses for sale here.