Vikings stadium: Retractable roof stats

So while I have a moment, I wanted to pass along some numbers that further explain why the Minnesota Vikings might (and/or should) pass on a retractable roof for their new stadium.

We noted Monday that the Arizona Cardinals have closed their roof for two-thirds of their regular-season games at University of Phoenix stadium. The chart adds figures from the other three retractable-roof stadiums in the NFL.

In all, there have been 216 regular season games in stadiums that currently have retractable roofs -- where the Cardinals, Houston Texans, Indianapolis Colts and Dallas Cowboys play their home games. The roofs have been closed for 60.6 percent of those games. And there has never been an open-air playoff game at those facilities based on team research. (The numbers don't include games when the Colts have had their roof closed but a retractable end-zone "window" open.)

Each team has had its reasons for closing the roof. The Colts have a rule that requires them to close the roof in weather under 40 degrees. The Texans consider opening the roof when temperatures are between 50 and 80 degrees. Former Cardinals quarterback Kurt Warner, meanwhile, preferred the roof closed for competitive reasons.

Does it make sense to add $25 million-$50 million to a $975 million project, plus higher annual operation and maintenance fees, for technology that historically has been used for three games per season, on average? Ultimately, that's the analysis that Vikings owner Zygi Wilf will consider in making a final decision.