I have to question the O.P. just a bit.
If the building work is done a voluntary basis, how are they running millions of dollars over budget? I understand that building materials have to be purchased, permits have to be pulled, etc. But in most construction projects, the majority of the costs go to paying the workers. The org doesn't really have that problem.
Did the org hire and outside engineering and architectural consultants to do the designing? Did the org hire larger construction firms to do the big work? Even at that, I have a hard time believing that their building deficits are "in the millions".
Am I missing something?