Our two storey house is about 5 years old. The one bedroom on the 2nd floor is freezing when it's windy outside. I poked a hole in the wall and could feel cold air blowing in. There appears to be insulation behind the drywall where I poked, but obviously something is wrong.

I noticed a draft under the baseboard when we first moved in. I put clear caulking along the floorline and that stopped the draft from blowing across the floor. It was windy and -23C the other day when I noticed the wall and floor to be extemely cold.

What's the best approach to fixing this? Do I rip the drywall and insulation off and redo it or is there a problem on the outside wall that needs to be fixed? Our house has vinyl siding and the room has hardwood flooring.

Someone suggested just ripping the wall out, finding the draft and stopping it with expanding foam. Someone else said I have to fix the problem behind the vinyl siding. I have no idea what to do.