If we’re going to address the housing-affordability shortage, two things have to happen. The first is obvious: more affordable units have to be built or developed. The second is less obvious: For the affordable units that already exist, insufficient as they are, affordability has to be preserved.

Preservation is necessary because affordability typically derives from public subsidies, such has low income housing tax credits, that expire – after 15 years, in the case of LIHTC. As the expiration nears, a private owner might well be tempted to convert the units to market rate or to sell to a new owner who will have no affordability restrictions. Such a sale might be particularly tempting in hot real estate markets.

A wave of coming expirations across the country prompted this ominous Blooomberg headline last week, “A lot of cheap housing is about to get very expensive.” The story drew from an Urban Institute blog post on a review of 1.2 million project-based rental assistance units around the country that found about one-third were at risk of losing their affordability status in the next couple of years. The Urban Institute researchers recommended that local preservationists (such as housing non-profits and land trusts) focus their efforts on units in “high-opportunity” or low-poverty areas, where owners’ temptation to convert to market rates might be particularly strong.

Vermont, mercifully, has benefited from a concerted preservation effort since the late ‘80s – a combined initiative of state agencies (Vermont Housing Finance Agency and Vermont Housing & Conservation Board) that marshal state and federal dollars to provide and extend subsidies, and non-profit organizations, such as land trusts, that step in to acquire properties before they disappear from affordability ranks.

A survey last year turned up 822 units in privately owned apartments in Vermont with subsidies due to expire before 2020. An additional 1,649 units controlled by non-profits were found to be eligible for new investments, such as capital improvements or subsidy-extensions, before 2020.

Whether Vermont will be able to maintain its historically high rate of preservation for these units will depend, in large part, on the availability of public funds to underwrite the needed subsidies and investments, and the outlook for that, at both state and federal levels, is dubious.

And even if Vermont could preserve the affordability in perpetuity of all the current affordable units, there aren’t anywhere near enough of them to meet the demand. Many more affordable units have to be developed, and more public money will be necessary for that, too. That’s money that won’t be available until political leaders make housing a priority.