You transport factories, forced labour construction camps, or construction ground units from somewhere else.
Construction ground units don't build things in C# like they did in VB. They only build fortifications for ground units.I stand corrected.
The Construction Equipment module contributes industrial production equivalent to 0.05 con facs.
A formation of 20 of these costs 144BP and 144 vendarite, and provides production equivalent to 1 con fac (which costs 120BP, 60 duranium, and 60 neutronium).
So, the formation carries a 12% cost premium over a confac, but doesn't need duranium.
The formation has 3600 troops, which requires 3.6 troop transport bays to move. That's a build cost of 72bp and a size of 3.6kt.
(Obviously you can't build 3.6 troop transport bays. My numbers here are just for comparison to a single confac. Adjust your formation size to suit your troop transport ship design.)
One con fac requires 1 standard cargo hold (50bp, 25kt) and a cargo shuttle bay (20bp, 0.5kt) to move. That's 70bp and 25.5kt for just one cargo hold, but you can add more holds without needing more shuttle bays if you want to move more than one per ship (although you'll need a big shipyard first).
Worth noting: the standard cargo hold requires 50 duranium, whereas the 3.6 troop transport bays require 18 duranium, 18 neutronium, and 36 mercassium.
In the very early game, it might be worth building and shipping construction troops rather than confacs for colony bootstrapping purposes, especially if you have a duranium shortage. You pay a little bit more in wealth for the troops, but you pay less for the shipyard and less for each ship. The big advantage, though, is that troops don't need infrastructure or population.
Heck, you can do both. At the start of the game, you have 4 GU training facilities just sitting there. Research the tech and use those facilities to crank out construction troops.
