** Stone falling off the siding / cracked siding
** In adequate attic insulation
** Gas leak at the furnace gas supply vavle
** Poorly vented sewer pipes
** Gutters not sloped properly towards downspout
** Missing metal trim at the eaves
** Bent soffit trim allowing a small hole in the roof
How old was the house??
Less than one year old. Encourage your friends who have new houses to have them inspected before the one year builders warranty runs out. This is sometimes referred to as a "punch-list" inspection.