My concern is from greenhouse heating up to temps too high for the plants. Outside light levels, even in areas mostly shaded, are going to be brighter than indoors lighting. So etoliation will happen inside much easier than outside. However, semps can also dry out too much during the winter time if in a dry location and exposed to dry winter winds. When in a small greenhouse, such as described, direct exposure to the sun can cause the greenhouse to heat up too much. Larger greenhouses or glass houses have much more volume (per surface area of plastic) to absorb or dissipate excess heat than the really small ones.