The Butler County commissioners should not rush hastily into construction of a building to resolve the county government’s growing office space shortage — and, commendably, they have been moving cautiously toward a decision.

But at the same time, the commissioners can’t ignore the fact that interest rates for borrowing are at historic lows. The county would be foolish to squander this opportunity for substantial financing savings, if it has the wherewithal and planning in place to move ahead.

It’s true that renting office space to ease or resolve the shortage remains a possibility — perhaps even a much less costly option, at least in the short term — but that might be cumbersome for coordinating and integrating some services, especially human services.

Ideally, from a logistical standpoint, the proposal to build a new office structure on the site of the former county prison on Vogely Street seems to make the most sense for resolving the space issue.

County Controller Jack McMillin wasn’t wrong in urging caution about the proposed building, with the county already paying in excess of $5 million a year toward the debt incurred for construction of the new prison on South Washington Street.

However, Bill O’Donnell, chief county clerk, might be right in challenging the controller’s 4-percent-interest-rate projection for the proposed project.

O’Donnell believes the project can be financed now at a rate below 4 percent.

To determine how best to address the office space issue, the commissioners voted in August to hire Butler architectural firm Burt Hill to do a feasibility study. Commissioner Dale Pinkerton has said that, once the study is completed, the county would know the best way to proceed.

The commissioners aren’t interested in opting for a plan that would mean a bigger tax burden for property owners, but an extra mill or two of taxation for a building now might end up saving taxpayers much more than if the building were built years from now.

Besides considering current financing costs, the commissioners also must acknowledge that construction costs will increase in the future, even if moderated for now by the current economic slowdown.

At the same time, the county has several sources of money capable of easing the project’s borrowing impact. They include savings from a lease of office space at the tier parking garage that will be expiring, and state money that must be used for utility and mortgage costs tied to state-mandated human services.

Current indications are that human services would be based in the new building.

The commissioners are not near the point when they’ll have to make a decision about which way to proceed. Between now and then will be the Nov. 8 general election and the uncertainty of what that balloting will produce.

While haste shouldn’t be a factor in the project, neither should be a failure to consider all alternatives — even a small tax increase — until a best option is identified.

And then there are the county’s voters. Their views should be sought by the four commissioner candidates while they are on the campaign trail in coming weeks.

The office building will be a major decision. For county government’s efficient operation and fiscal health, the right decision must be made.