The FFIEC issued an Interagency Q&A for Reg Z Reimbursements that was revised in 1998. This is what it says about construction loans:
Q. How will disclosures containing information properly estimated under 12 CFR 226.5(c), 12 CFR 226.17(c), and Appendix D be treated for reimbursement determinations and computations?
A. If an APR or finance charge is in error for any reason other than a properly made estimate, the determination of whether the error constitutes a reimbursable overcharge will be made using the estimated information as disclosed. At the creditor's option, reimbursement will be based on either:
(1) The actual amount of loan advances, with consideration given to the amount and dates payments were actually made by the borrower; or
(2) The disclosed amounts of time intervals between advances and between payments.
The basis selected shall be applied, using the lump sum or lump sum-payment reduction method (at the creditor's discretion), to all loans of the same type subject to reimbursement.