Attic question.

Ok I have noticed an issue in my new build regarding my roof. So this week we had the cold spell and lots of snow. All the houses next to mine had snow on them all week until the thaw today. With my house the snow has been coming off the roof since Sunday. I cannot understand what's going on because my attic is already insulated with rockwool to 300mm. Then between my rafters of the roof I hand insulated boards installed in-between the rafters sealed with foil and and osb board over them. I'm using my attic as storage. I have a stove in my house that was on all day for most of the week.

Is there heat escaping in my house that im seeing this? Who can I get to access this and see if there is a problem?

TIA