Most of the time, he said, he starts roof work at 7.30am and temperatures are likely to be a little lower - around 40C.
"You have to get through it fast and get it right the first time, you don't want to have to go back up."
He said he had to drink plenty of fluids, and ensure all roof jobs were booked in early.
"Health and safety is so important. It's just not safe in that heat if it gets too hot."
Polyester insulation was a more skin-friendly alternative to the heat-activated itch in fibreglass too, he said.
Some clients had gone out of their way to help Mr Kalin stay cool.
"Some folks have hosed down their roofs or even taken tin sheets off it. But we don't expect clients to do that."
At least crawling under the house to complete the insulation job offered some cool respite.