Our new one is a 20x14' rhino and we're very plaesed with it, it has double doors and a ramp into it as our disabled group have use of it, we also have some people without their own greenhouse who have a space in it :)
it has shading all along one side, blinds that we can raise and release, also we got staging and racks as we are using it to bring on plants for the annual plant sale, once that is over, members can grow in there, ours is on a paved base , it also has 4 vents either side and large rop bars to hang baskets on ;D