Can air travel through walls or gl--science experts?

So heat and temperature all have to do with the speed of molecules. Faster speed = higher temperature. When these slow molecules hit the faster molecules, the speed is changed thus the inside of your house will eventually get colder. It doesn't matter how much isolation you have, unless you have a literal vacuum in between your walls. Alternatively, there could be small spaces in the seal of your window which letting air come through. You can actually put some tape over the edges to try and stop the amount of cold air getting through.