lesschumros:
In another blog I explained the reason why bnei torah where black and white. it is not a matter of frumkeit, but a matter of how one wants to be perceived.
In my opinion if he feels more comfortable in jeans working around the house, let him wear jeans. I know of hoshuv people who have “work clothes” for the house. i think though, that many people who are used to wearing “yeshivish” clothes may be uncomfortable donning jeans even in the house, and even in private. It is a personal preference of what youre comfortable with.