Something I have been wanting to do for a while is see how air tight I have managed to make the house, but without paying £hundreds for an official test.   So take one old desk fan. Some bits of wood. A large piece of cardboard and a roll of duct tape.   The first thing was just to run the fan on full speed and go around the house looking for leaks. I found a leak under the front door where it was not sealed to the floor properly. A leak in the loft at a tricky detail b