Windows in Washington fail on a wet sill or on a frozen night, and those are not the same opening. On the marine side, wood sash drinks the long damp, paint peels at the stool, and condensation on a cold pane drips into the trim until it softens. Wind-driven rain finds a gap that a straight rain would have missed. On the inland side, a hot afternoon against a hard freeze dries seals, and wind whistles across open lots. Fog between panes means the seal has given up, wherever you live.
Walk the house and separate the rooms that sweat, the rooms that leak, and the rooms that only feel drafty. A bath window that drips may be a fan problem sharing an opening with a bad sash. A stair window that leaks only when the wind comes from the south needs sill and flashing talk, not a speech about every elevation. Say whether the frames are wood, vinyl, or metal, and whether the house is an older drafty place or a newer one with a few failed units.
Ask what the work includes: the frame, the flashing, the interior trim, and the seal against the siding. A new unit set into a wet wall, with the rotten sill left in place, only hides the damage. On the cold east side, ask how the frame handles a hard freeze and whether the meeting rails actually latch. On the wet west side, ask how water is supposed to leave the sill instead of sitting in it until the stool goes soft.
If a claim is part of this, keep photos and do not replace the only evidence before the damage is documented. Otherwise call ready to name the rooms, the floor, and the wall that takes the weather. A coastal bluff and a basin lot do not hand you the same window problem. Say which one is yours.
The opening will keep taking weather while you compare brochures in your head. Name the bad sash, the town, and whether the wood is soft or the glass is only fogged. Call the number on this page.