You probably dont want to be constantly looking after your greenhouse yourself opening the windows when it gets too hot, going round every few days and all the rest. Its much easier to get automatic systems to do these chores for you.
To water your plants, you should install irrigation systems. These are basically small pipes that run underground and slowly release water into the soil greenhouse models are very similar to the ones used on commercial farms, only smaller. These irrigation systems allow you to quite simply and easily set how much water your plants are getting with a tap, instead of you having to go and water them all by hand. Many plants will also respond better to being watered at the roots than they do to being watered on the topsoil, and they will often grow bigger, which is an added bonus.
The other thing you need is a cooling system. While it might seem odd to have a cooling system in a greenhouse, it is possible for them to get so hot inside that all the plants will get cooked and die, especially in a hot summer. Again, the cooling system will be a series of underground pipes, allowing hot air to be taken down underground and stored during...