Radiant tube heater control question

Copntroling gas tube heaters

We have a large factory complex that was converted to a museum. With the exception of the lobby/visitors entrance which is nicely heated and air conditioned with a forced air system, the interconnected buildings are heated with radiant gas fired tube heaters. In the AM, the site manager turns all 14 tstats up and when he leaves at 4PM, he turns them all back. Here's the problem: with some days having no visitors, why have all of those tubes cooking away? But if he waited for the first visitor to arrive, he would then have to take the 10 minute hike around the place to hit those tstats, abandoning the front desk. We've already looked into motion activated switches and there's logistical problems. What we need is a remote method of turning up those tstats. With a $5K gas bill in January, we can easily justify a costly installation. Is a DDC/computer the way to go?
We're looking into seasonal changes in our hours, which could be the best option. Visitors tend to have their coats on, so the buildings can sit there at 50-55 degrees and the radiant heaters provide almost instant heat. (These buildings do not house delicate antiquities) Any thoughts before we hire an engineer?