There's no problem with rent a room applying here, particularly if the person in question is staying in b&b or similar short term accommodation during the week while working away (although, even if they're paying to rent a room elsewhere, which would be available 7 days, it's still unlikely to be a problem).
I presume when there's bank holidays, annual leave etc, they return and stay in the house they own.
Presumably all their stuff will still stay in that house, other than a bag they pack and bring with them while working away.
Clearly, someone who stays elsewhere for commuting purposes hasn't changed their residence.