Now I see the pics I think the guttering is suspect, any blockage behind window elevation [and yours looks quite high and likely to collect a large amount of leaf litter]will result in regular spillage over gutter or flashing causing long term damage.Any high [taller than guttering] tree's within 100metres?
Could not see any guttering to garage does it drain to rear?
Ventilation to rooms should be permanent, trickle vents to double glazed units and wall mounted vents.
Could not see any guttering to garage does it drain to rear?
Ventilation to rooms should be permanent, trickle vents to double glazed units and wall mounted vents.