Would it be possible to introduce the dog to some of the workers when they arrive?

I would really suggest doggie daycare or a friend/family home until your project is finished. We have a dog who came to us with crazy anxiety, that has taken us YEARS to just reduce her anxiety levels from noise. Even if we are home with her, we can't comfort her. She doesn't "calm down" until the noise stops. We take her away from home or allow her to hang out in the fenced yard if it's a short period of time. The best solution has been for her to stay with family while the noise is happening. PLEASE don't think he will just "be okay". He can't help being afraid. The fear intensifies and only causes more issues long afterwards. I hope you figure out a solution, so he doesn't end up with permanent issues.

Thundershirt? Doggy CALM drops? very natural ingredients. I also use them. not kidding. Anything to calm. I keep my reactive poodle mix in a room with NOTHING going on..small corner. Bedding, toys...HER SPACE. Every little sound she goes beserk. All day. I also give her attention when she is quiet. Soft brushing calms her down, too. It's a very soft bristle type brush. THen I leave quietly fingers crossed :)

Trazodone for dogs. For other non prescription remedies available over the counter look at L-theanine, Magnolia extract and other plant or milk amino acid extracts that will calm dogs. But Trazodone is boss and a call to your vet should get you a script.