If they are steaming up while the vehicle is parked for long periods, it sounds very much like you have a leak somewhere. To help trace this, check all carpeting. Any very damp patches indicates that water is getting in, possibly because a rubber grommet has been lost or damaged, or a drain hole has become blocked. You will need to lift as much as the carpeting as possible to check that none of the round drain holes on the underside of the car have lost their rubber stoppers.
Check in the boot too for puddles of water. Lift the boot (trunk) liner and inspect thoroughly any signs of dampness. If the spare wheel is stowed here, remove it as this recess is the lowest point and where water will gather. Water in the boot usually means a hole or even a hairline crack in one of the rear wheel arches. Another possible culprit is worn door seals.
Check in the boot too for puddles of water. Lift the boot (trunk) liner and inspect thoroughly any signs of dampness. If the spare wheel is stowed here, remove it as this recess is the lowest point and where water will gather. Water in the boot usually means a hole or even a hairline crack in one of the rear wheel arches. Another possible culprit is worn door seals.