Severe draft coming from floor

[sir_78]

Hey all its my first post and hopefully I didn't screw this up and put it in the wrong place.

So I live in Saskatchewan and its f'ing cold now. Bought a house 4 months ago and there are 2 large bay windows. The floor around the windows is really cold (have carpeting) and noticing a draft (I mean it feels like a window is open). I assumed it was the window and bought some of that shrink wrap and sealed up the window. That didn't stop the draft or change anything.

I drilled a few holes in the wood ledge and under window (in drywall) and seems to be well insulated as no drafts came through holes.

Next I though well maybe its just cold air coming through the register that sits right below the window, so I stuffed an old shirt to stop airflow.

This morning I noticed the floor about 4-5 feet away from the window is freezing (and again its carpet). I went over to register and its very cold to touch, pulled out cover and can feel cold air screaming up (like to the point that I put a piece of paper over the register and the paper blew away). I pushed back some of the sheet metal and noticed an open space under the floor where the cold air is coming from.

Naturally I went to the basement to check the ceiling (which is drywalled and popcorned Ugh!) and the ceiling is not cold at all directly under the spot that its cold on the main floor.

Any ideas before I start tearing apart my floor?

[HVAC_Marc]

if you cant get under the bay window the only way to get to it is through the floor.

[STEVEusaPA]

Why don’t you have someone shoot it with a thermal imaging camera first to see if you can get some insight as to where to start.

[David Goodman]

Is the bay window cantilevered past the foundation wall, or does the foundation jut out with the window?