The nation's two largest home-mortgage lenders have quietly begun tightening their standards on refinancings -- a series of policy changes that will affect thousands of American property owners in the months ahead.

Though no announcements have been made to the general public, both Fannie Mae (the Federal National Mortgage Association) and Freddie Mac (the Federal Home Loan Mortgage Corp.) will apply tougher requirements to certain refinancings closed after Sept. 1. Local lenders across the country are putting the new standards into effect this month, however, because many loans originated now won't close before the deadline.

The key changes affect the ability of homeowners to "cash out" -- tap their inflation-fed equity through refinancings that put new dollars into their wallets. Cashing-out via refinancing is common and works like this:

Let's say you bought your home 10 years ago for $75,000, with a $60,000 deed of trust, or first mortgage. Thanks to strong appreciation in local home values and deft improvements to the house by you, the property is now worth $150,000. Your mortgage is now paid down to $50,000. If you wanted hard cash in your pocket -- for investment, pleasure, kids' educations or whatever -- you could refinance.

A 90 percent refinanced loan against your home would be $135,000, more than double your original $60,000. After paying closing costs and loan-discount and sundry other fees, you'd probably end up with something in the range of $82,000 in hard cash, all tax deferred ($135,000 minus the $50,000 existing loan minus $3,000 in fees).

In a nutshell, that's a "refi cashout," and your new loan is more than you need to pay off your existing first or additional home loans, plus closing costs and new mortgage-processing fees. You walk away from the table with hard currency.

Under Fannie Mae's and Freddie Mac's new standards, you'd be limited to a cashout of only 75 percent of the current appraised value of your home. Immediately prior to the policy switch, both lenders' standards had been 80 percent maximum loan-to-appraised-value.

The change would hit you far harder if the real estate you were refinancing happened to be a second home at the beach, the lake or a small rental investment home. Both Fannie and Freddie are shutting their windows to second-home and investment-property cashout refinancings altogether. Fannie Mae won't touch them on any loan closings after Sept. 1; Freddie Mac pulled the plug earlier this spring.

That could prove to be a shock to certain owners, particularly in fast-appreciating resort areas in the Northeast and elsewhere, who expected to be able to pull money out of second homes anytime.

Owners of first and second homes still will be able to refinance. They just won't be able to extend their debt to the hilt as easily, or obtain the sort of competitive rates and terms available through Fannie and Freddie.

Fannie Mae and Freddie Mac purchase loans originated by local mortgage lenders -- billions of dollars worth every year. The standards they set on a wide variety of mortgage matters, from the precise wording in your loan documents to the rate on your note, have vast impacts nationwide. Local lenders who don't conform to Fannie Mae/Freddie Mac standards can't sell their loans to them, and are thereby cut off from the most dependable sources of capital in the marketplace.

Fannie and Freddie will still fund "no cashout" refinancings -- that is, where the borrower is not trying to walk away with new dollars in his pocket -- at loan-to-value ratios up to 90 percent.

"Fannie and Freddie are sending an unmistakable signal," said William A. Roper Jr., president of Boston-based Mortgage Refinance Corp., a mortgage banking firm that does 80 percent of its business in home-loan refinances. "They see greater risk {of default and foreclosure} in cashout situations."

The upshot for you? Think of your house as shelter first, piggy bank second. And think of the piggy bank as being just a little harder to shake money out of without selling it outright.