How often do teams open their retractable roofs?

There is no more joyous day for baseball fans in Toronto than the first home game with Rogers Centre roof open. Once they pop the top, fans don’t want to go back to the hermetically sealed environment designed to protect Canadian ball fans from the elements.

The Rogers Centre was the first retractable dome in baseball history when it opened in 1989. Since that time, Chase Field in Arizona, Miller Park in Milwaukee, Safeco Field in Seattle, Minute Maid Park in Houston, and Marlins Park in Miami joined the ranks of convertible stadia. The league created a set of guidelines for retractable roof usage to ensure fairness and competitiveness is consistent across the board. 

The debate in Toronto is unique to the battles held in other, warmer cities. While sun-starved Canadians wish for fresh air at every opportunity, fans in warmer climes appreciate the comfort of air conditioning.

The players on the field must also adjust to the shifting conditions and changes to their playing surface. But make no mistake, the roof is about the fans.

While reporters that cover the game express strong dislike for closed roofs and indoor baseball, the fans who are asked to sit for hours exposed to the elements have a different view.

Here’s a look at the policies/usage of baseball’s retractable roofs and what it means to the players and fans at these parks.

Out from the cold

The opening of the roof is an anticipated event each year in Toronto. While some fans want to pop the top on the first sunny day of the year, it often happens a few weeks into May. This season, Toronto played its first “outdoor” game on Saturday afternoon. The especially cold winter in Toronto meant the roof wasn’t eligible for testing until later in the year.

The roof in Toronto is a hot topic for reasons outside the fan experience. Pitching indoors is known to do wonders for the knuckleball of R.A. Dickey, such that the Jays nominal ace prefers pitching with the roof shut whenever possible.

As much as winning games is important, the fans speak loudly and Dickey’s start on Saturday came with the sun pouring onto the green Canadian rug. After pitching well against Oakland with the top popped, Dickey preferred not to discuss the state of the roof.

The Rogers Centre does play differently with the roof open versus closed. Jays reliever Steve Delabar that one reason the ball might carry more with the roof closed is, especially when it shuts mid-game, the sun can make it very dry inside the dome, allowing the ball to really fly.

Milwaukee operates under a similar principle to Toronto - their outdoor games mainly during the summer months, while the Miller Park roof stays shut early and late in the year. It, too, is known as a bandbox where the ball carries and home run ball fly freely.

According to Baseball Reference, the Brewers played just over half their games with weather conditions other than “roof” or “dome” last year. 2005 ranks as the most with 52 “outdoor” games while the next year, 2006, is least with just 30 games with the roof cracked. These measures are a little crude, it should be mentioned.

BR’s numbers show a similar split between indoor/outdoor to Milwaukee, with 40 “open air” games last season and a record of 57, set in 1999.

Both the Blue Jays and Brewers appear to treat their stadium as an outdoor facility built to avoid rainouts, though these  facilities lack the air conditioning capabilities found in warmer weather parks. Still, better out than in.

In from the heat

The newest retractable roof in baseball is also its least frequently used. Not only does the roof open at Marlins Park, it features an “operable wall” and three panels to provide all manner of fresh air into the house that taxpayers built.

With two full seasons in to its time hosting Giancarlo Stanton and friends, the roof doesn’t appear to get much in the way of use. Using Baseball Reference’s Play Index, the game condition at Marlins Park was only classed as “open” 15 times in 2013 and eight times in 2012.

The weather in Miami necessitated the creation of the Marlins expensive new building. Miami must balance the traditionalist need for an outdoor, open-air game with the comfort levels of their fans. The frequent rain in South Florida is one concern, the intense heat and humidity is another.

The plight of the Marlins is similar to those experienced in Arizona and Houston. The Astros ballpark looks widely different with the roof open, a treat Astros fans are rarely granted.

According to the Play Index, only 11 games were played with the roof open each of the last two years. The trend in Houston is decidedly towards leaving the roof shut, as only one season in the last 10 featured more 20 open air games.

Earlier this year, the Astros front office promised to try and open the roof more. The rules that govern the lid at Minute Maid Park, as written, make it tough.

...the roof is closed for the threat of rain, threat of sustained winds above 30 mph, temperatures below 65 degrees for a night game and air temperature or heat-index readings above 88 degrees for a night game or 84 for a day game.

Astros general manager Jeffrey Luhnow told me he has a preference for the state of the roof - one he wanted to keep to himself. He expressed the same need to balance the needs and comfort of all fans, not just those who long for an authentic baseball experience.

The players themselves keep their focus on what’s within their control, but they have their preferences. Former Astros starter J.A. Happ started 59 games for Houston in his time with the club, only five of which came with the roof open. “it’s just too hot to play with the roof open” Happ stated frankly. Like most players and fans, roof open is his preference but it can be extra challenging “if you’re standing on the mound with a hot breeze in your face."

Arizona doesn’t have the same humid conditions found in Houston and Miami. Just baking desert heat, a factor that keeps their roof closed more than half the time they play at home. Just 25 time last season the Diamondbacks rolled back the roof and walls to give their fans the benefit of fresh air baseball.

While the roof remains closed most time for Diamondbacks action from June to September, the team cracked it open for Memorial Day, when the temperature reached triple-digits. The following message played on the hotline fans can call to get up to date information on the roof.

Those high temperatures might make for a long day, but this practice was the exception to the rule.

Russ Amaral is the Diamondbacks Vice President of Facilities and Event Services and he’s the man who makes the decision to open or shut the roof.

He explains that he looks ahead and makes decisions on a series-by-series basis, factoring in not only the temperature but wind and humidity forecasts. The roof and wall panels have set wind tolerances they must consider. Temperatures were high this past week but low humidity allowed Arizona to open the roof for their series against the Padres.

Another big factor in Arizona is the projected attendance. The team, with the support of their season ticket holders, want to ‘push the envelope’ and crack the roof as often as possible. If some ticket holders aren’t comfortable with the roof open, the team often moves them to a better shade section of the stadium. With a full house, that isn’t always possible.

Amaral adds that the sun typically moves off the field and seats around 6:15 local time, so when the humidity is low (like this week), they open the roof an hour or so into the game. They pre-cool the stadium with their powerful air conditioning systems and crack the roof once the worst of the heat is finished for the day, around 10 minutes before first pitch.

The Safeco Anomaly

Seattle’s beautiful Safeco Field is different than the other retractable roof facilities in baseball. It isn’t actually a roof as it is still open air. It is more like a beach umbrella that redirects rain away from the field. When it rains, the water can still blow into the stadium and bullpens.

Closing the roof doesn’t change the way the game is played on the field much, but one former Mariner notes that closing the roof does have one big impact - outfielders tend to lose more balls in the lights with the roof shut. Something about that backdrop make picking up the ball out of the banks of floodlights becomes extra challenging with the roof in place.

The Mariners play fewer indoor games than any of their cousins in engineering achievement. The climate in the Pacific Northwest makes it possible for the Mariners fans to enjoy the best of both worlds - dry games and fresh air, comfort and the legitimacy that a sealed stadium simply cannot offer.

Teams want to make their passing customers happy and comfortable - this is the original reasoning behind building a roof in the first place. How they go about doing so is a work in progress.