Navy Federal Credit Union, the largest credit union in the country with 4 million members, offers a zero-down option for qualified home purchasers coast to coast with no mortgage insurance. (Rick McCleary)

Who says lenders need to charge you a down payment when you take out a mortgage in this era of hyper-strict underwriting?

Just about everybody:

●The biggest sources of home loan money — Fannie Mae and Freddie Mac — won’t fund a loan without a down payment. And if you put less than 20 percent down, they require private mortgage insurance.

●Federal banking regulatory agencies have proposed — but have not yet finally adopted — a regulation requiring a 20 percent minimum down payment as the new standard for safe lending and best pricing.

●Congressional critics complain that the Federal Housing Administration’s current 3.5 percent minimum down payment is part of the reason the agency is in financial hot water. They want 5 percent down at least.

●Financial analysts and mortgage industry experts argue that requiring some amount of “skin in the game” is essential to give borrowers a stake in the transaction.

But hold on. Two prominent federally chartered credit unions beg to differ with this consensus opinion. They have quietly been running what they consider to be successful, carefully administered zero-down-payment programs for much of the past two years, and they are seeing almost no defaults or foreclosures.

Navy Federal Credit Union, the largest credit union in the country with 4 million members, offers a zero-down option for qualified home purchasers coast to coast with no mortgage insurance. On top of that, it allows “seller concessions” — contributions by sellers of homes to defray buyers’ closing costs — as high as 6 percent of the home price.

The maximum loan amount is $1 million, but typical loans are in the $200,000 range. The program is targeted especially at first-time purchasers because they often are short on down-payment cash but may otherwise be creditworthy. Navy Federal says it has closed $740 million of these zero-down mortgages in the past 12 months alone. The credit union retains all loans in its investment portfolio and services them on its own.

As you might guess, there are some key qualifications: You have to be a member of the credit union or an immediate relative of a member. (Membership is open to people in all branches of the military, active and retired, along with defense-related contractors.) The credit union estimates the total potential reach of eligibility nationwide is 12 million people. You need to pass underwriting muster in terms of income and reserves, and you need moderately good though not perfect credit scores. Delinquencies on the program to date: well under 1 percent, according to Katie Miller, vice president for mortgage products.

Meanwhile, NASA Federal Credit Union has started marketing its own version of zero down. It is restricting loans to qualified members buying homes in the Washington area, but it might expand to other areas, depending on local housing market conditions. The maximum loan amount is $650,000. Seller concessions are capped at 3 percent. Underwriting is rigorous, and preferred FICO credit scores start in the mid-700s. Delinquencies over the past year and a half: zero, according to Bill White, NASA Federal’s vice president for real estate lending. Foreclosures: also zero.

So what’s the significance of these two programs for the down-payment debates underway on Capitol Hill and among banking regulators? Should the government mandate 20 percent down for everybody? Ten percent? Should zero down ever be permissible?

Tom Lawler, head of Lawler Economic and Housing Consulting, says that as a general matter, “zero down payment is just bad public policy.” Frank Nothaft, chief economist for Freddie Mac, maintains that “the more equity [cash upfront] you have, the better” the loan is likely to perform. Both Lawler and Nothaft agree, however, that with strict underwriting at application and intensive servicing — getting in touch with borrowers at the first hint of trouble and working with them — zero-down loans can perform well in healthy housing markets.

The Department of Veterans Affairs has offered zero-down loans for years yet has a lower default rate than FHA, which requires 3.5 percent. Although the Navy Federal and NASA Federal programs are relatively young, their minimal delinquencies could have an important message for regulators: The size of the down payment is just one piece of the puzzle.

Smart underwriting and hair-trigger servicing that intervenes with solutions when borrowers hit rough patches may be just as important.

Or more.

Ken Harney’s e-mail address is