"Since the interest rate for the 1st $20,000 in your CPF Ordinary Account is higher than the interest of the HDB Concessionary Loan, it would not be prudent to transfer the funds from your CPF Ordinary Account to pay off part off your housing loan as the yield earned on the CPF Ordinary Account is higher than the interest expense of the housing loan"
"An additional 1% interest will continue to be paid on the first $60,000 of a member’s combined balances, with up to $20,000 from the Ordinary Account (OA). The additional interest received on the OA will go into the member’s SA or RA to enhance his retirement savings"
So it make sense to keep the first 20k of your OA as it will earn higher interest compared to HDB loan interest rate. Anything above 20k are better off used to settle our HDB loan.