The skyrocketing U.S. real estate market is making it difficult not only for Habitat to put new partner families in homes, but it can also make it difficult for Habitat families to stay in them.

Tyree Hawkins' monthly payments have gone from $525 per month to $865, reflecting the increased tax valuation of the school bus mechanic's Habitat house. He is making payments on a $120,000 mortgage, but Fairfax, Va., tax officials say his home is now worth $450,000 in a market that is spinning dizzyingly upward.

Twenty miles away in Alexandria, Kesha James has seen her monthly mortgage rise from $515 to $954 in the past 18 months, all in taxes. Her modest Habitat house, according to tax officials, is now worth about half a million dollars.

In some parts of Northern Virginia, according to a story in The Washington Post, home values have tripled in the past three years.

Area Habitat affiliates have launched a campaign to convince Northern Virginia officials that, because of deed and loan restrictions on Habitat homes, the houses should not be assessed at market rates, and they are making progress. Fairfax County has approved some Habitat homeowner appeals, and Alexandria city officials appear to be lending a sympathetic ear.