Sometimes the lower part of the chimney releases heat. When the chimney is in use (or recently has been). In that case only the upper part is warm, meaning there is no  defect.

This construction is to support the top of the windows. Depending on the material used for the lintel, it may conduct more heat than desired.

Single glazing is the easiest & oldest method used for glass windows. It is not the most energy-efficient.

The door and/or glazing used in the door are poorly isolated.