Designing a residential radiant heating system to heat properly is relatively easy, if you have the proper information and follow some simple rules.
A zone is the area each loop of tubing covers, you will be able to control the flow in each loop with a ball valve, also each loop will have a ball valve on both ends so you can shut off one loop without shutting down the complete system..
A thermostat can control from one to several zones.
It is not practical or desirable to put a thermostat in every room.
Sleeping areas and baths that are joined are generally controlled by one thermostat. Areas that are open to each other are generally controlled by one thermostat.
You will need at least one thermostat for each floor.
A garage or shop, no matter what size, needs only one thermostat
A basement normally needs only one thermostat but it might need two. If it is a large daylight basement it could need one for the front and one for the back, or if it is large and has two different uses such as sleeping and playing.
The main floor usually needs two thermostats, one for the living area and one for the sleeping area. Add one if the bed rooms are not in the same area or if the master bed room is very large.
Upstairs usually need only one thermostat. Add one if there is over a thousand square feet.
Do not heat or place thermostats in open loft areas.