GpsFrontier has brought up a very important factor in the timing and construction of an
ebb and flow system that is outside in ambient temperatures.
Heat is a real problem. In some places cold can also be a problem.
The ideal root zone temperature is 75-78F. The roots can take up oxygen and
nutrients best at that root zone temperature.
If you live in an area where the ambient temperatures can get to 90+ for extended times, its a good idea to run your flood times more frequently to keep the root zone at the optimum temperature.
You can also do other things to help. Putting the reservoir into the ground will help keep the
nutrient solution cooler. This is true regardless of the type of system you use.
Installing a chiller on larger systems can be a must in some locations where its impossible to keep the reservoir temps down to a reasonable limit.
Putting a temperature probe into the root zone periodically during the drained cycle will tell you if your root zone is getting too hot. If so, increasing the flood timing will sometimes resolve that problem.
In areas where it gets cooler than 50F at night, that also can create a real problem. It too can be resolved and the growing season extended by using more frequent floods. Again, monitoring the root zone temp is the only way to tell if its getting too hot or cold.
I live in Northern Florida, and have used NFT almost exclusively outside in enclosed growing areas. I sometimes forget that most other places have to deal with larger temperature differences than I do.