You will need to consider what type of foundation to construct or install. There are several choices including gravel, wood, cement, brick or even none at all. You also need to decide whether you are going to cover the floor with linoleum, carpet or tile. Some floor heating systems can function within these, The type of floor covering will also dictate how much time and effort will be required in cleaning it.
Where to site your new glasshouse is another important consideration to take into account. Dependent on where you live, what variety of trees are around your home in conjunction with other factors, you may only get a a couple of hours sunshine per day or over a dozen. Climates differ as well in the amount and severity of wind, rain, hail, snow and other variables.
Geographic location is a another element that will play a big role. For example, northern latitudes will get longer hours of summer sun, but considerably less in the wintertime. The amount of sun per day is a major element in planning any greenhouse, although to a certain extent, it can be compensated for with artificial lighting and heating systems.
Beyond hours of daylight, the amount of heat and humidity is heavily affected by climatic conditions. Even in northerly latitudes there are substantial differences. In Northern Idaho, the summers are dry, which would imply a greater need for watering systems. By contrast, summers in the Northeast States such as New Hampshire, are a lot more humid which would mean that you will need to water less.
You need to analyze all those relative to the proposed size and positioning of your planned greenhouse, while being constrained by the options available on your particular property.
You may well have trees close to the house in one area, but further away on the other side. You might have a flat area suited for a greenhouse, or a slope l which could be leveled off in day with a bulldozer. Also take into consideration, the amount of wind, hail and rain you are likely to get in one area versus another.
Even though the average amount of wind and rain is, of course, the same over your entire property, the exact amount at the site of your greenhouse will vary. As an example, trees can block wind and rain while high walls may shield another side.
The amount of rain on the greenhouse will dictate what type of drainage is needed around it. Think about orientation of the doors and windows, along with the location on your property. Wind effects can be severe when you open the door while water or mud may have a tendency to pile up around the outside walls and the doors.
It Is not necessary to become an architect to build or install a greenhouse but when you look at plans, try to think like one. For those more concerned about gardening rather than construction, that is a challenge. However you will have more time for plant care in the long term if you spend some time thinking about building now.