I built a small germination box. It is 20 inches deep by 30 inches wide and 18 inches tall.
It fits a single 10x 20 seed tray with a 4 bulb 24" long T5 grow light. Using 6500 temperature buLbs.
The box is made of 3/4" insulating hard foam panels with reflective coating on inside side.
In the garage, where temperatures hit a low of 45 degrees, the box held between 78 and 82 degrees with the seed heat mat.
When I turned on the grow lights, temp hit 113 degrees.
So I made an alternate front that I drilled 12 1/2" holes into. This dropped the temperature to 92 degrees with the mat turned off.
I will need to buy a temperature thermostat controller for the heating pad to turn it off when the lights are on.
Seeds were planted 2 days ago in it.
I also have started sugar anne peas in the greenhouse. They are coming up nice, need to be planted soon.
I plan on putting the around the tomatoe cages.