Insulation issue, help needed

Hello, I'm hoping someone here can help, I rent a property above my landlord's garage.
There are some insulation foam slabs under my floor, and this is now covered with some silver foil insulation stuff, which was to get rid of the draughts, so far so good.

Now last week my landlord has replaced his previous two large aluminium garage doors, one with a wooden frame that holds wooden boards and made to look like a door, (but is basically just planks nailed to a frame and then sealed all round,) and the other door (which they use, is two bespoke wooden doors, which doesn't have a seal at the bottom, but are quite close to the ground, and are sealed top and sides.

Since these wooden doors and boards have been put up, my flat above is MUCH colder, and neither myself or my landlord can understand why. There is no detectable draught coming from the doors when closed, or from the boardy bit. But even with three heaters on in the flat, there is a foot-high layer of cold air constantly and I'm struggling to get the room to room temperature. Even when the room has warmed up and a steady 20+ degrees, there is this constant layer of cold air about a foot from the floor and once the heaters are turned off (I used to be able to warm the room and then sit in it happily,) the heat just disappears within 30 minutes and then it's just cold again, averaging about 8-11 degrees (depending how cold it is outside.)

Any ideas?
Thanks in advance for any knowledge/help.

 

Thanks. I've been through 8 winters there though. This is since the new doors etc were put on.

 

Well it's not windy, just got home and even with 2 heaters on, it's 10 degrees. Sumat not right. We don't understand how it was warmer with aluminium doors that had gaps all round! .