Greenhouses are a space to create as close as possible the environment required for your plants to flourish and produce healthy plants.

You must heat your greenhouse if your plants require warmer temperatures than the current inside temperature of the greenhouse or cool the temperature if it is too high.

Remember you must create as close as possible an artificial environment the plants normally thrive in. This also includes providing the correct amount of light or shade. Putting shade over plants to help cool them is very bad for plants that require full sun (put a tomato plant under shade will result in a sick or dead plant).

The reverse, putting plants in full sun in winter to heat them can also be bad thing to do, ( putting a fern in full sun to warm it produces bad results in most cases).

Bottom Line! Study your plants requirements, in greenhouses that are used to over winter house or patio plants and there are usually many different types of plants too sheltered you must find a medium, some made be set back a little while others slow down a little but still thrive, all will rebound and return to normal when returned to the patio and house.