Quote Originally Posted by JoshJP7
The enclosures I will be building are 4ft x 2ft x 18inchs and I need to know how many flex watt feet I am going to need?
What is your aniticpated arrangement on the tubs, and ambient temperature where you expect to put the racks? On our adult rack, we have 1' of 11" flexwatt for each 27-qt tub (two tubs per shelf, long side out), and our baby rack has 2' of 3" for each shelf (four tubs per shelf, short side out), which in our case is fine because our normal room temperature is only slightly lower than the desired ambient temperature (temps in the tubs run slightly higher than room temperature due to low air flow, and thus low heat loss).

If your ambient room temperatures are expected to fall below an acceptable range, you may need to reinforce the "hot" side flexwatt with "cool" side flexwatt to keep your ambient temps in the 70's.