More than 40% of wall space is glass
This is a technical point from the International Energy Conservation Code. If you’re designing a sunroom, you and your architect will determine the actual ratio of glass to enclosed wall space that will work for your room.
A sunroom is fully enclosed. A sun porch is open to the elements rather than having full windows and walls between the indoors and outdoors.
May or may not be heated or cooled
Sometimes the sunroom is fully integrated into the house and is attached to the central HVAC system. If not, it may have a separate heating or cooling unit mounted in the sunroom. If it is not meant to be heated or cooled, it will often have fully insulated doors that can close it off from the rest of the house when the temperatures are extreme outside. This option might sometimes be called a three season room.
Attached to the house
If it’s unattached, it might be called a greenhouse, conservatory or summer house.
Solarium, Conservatory, Greenhouse, Orangerie
There are a lot of names for interior sun spaces. A solarium technically has a glassed roof, as would a conservatory, greenhouse and orangerie (or limonaia). For the purposes of this blog, I’m going to be very liberal about my definition of a sunroom. Any of these would count for me, and I’d consider myself lucky to spend time in any of them!