Windows in Pittsburgh take valley wind, a long freeze, and frames that are sometimes out of square because the house sits on a moving hill. Double-hung wood, later replacements, and odd sizes share the same older houses. Sills rot. Sashes bind. Basement windows on the uphill side are half in the soil and take water from the slope. Downhill windows look out over a drop and take the weather with nothing to block it. Describe the side of the house, not a generic opening.
A fogged pane or a failed balance can be a repair. A soft frame, a leak under the stool, or a sash that no longer sits in a racked opening is more. Insert work leaves the old frame, which is a problem if the frame itself is the twist. Full replacement shows whether the wall stayed dry. Say how many, and which rooms are cold even when the heat is running. Storm panels still hang on a lot of these houses. Say if yours do.
Condensation shows up all winter in a closed, humid house. Sweat on the room side is not a broken seal. Fog between panes is. Water that appears inside only when rain runs down the hill at the foundation may not be the window at all. Say if the stain is at a basement hopper on the buried wall. Upper sashes that rattle in a valley wind are a draft call, and they make the furnace look small. Mention the wind if that is when you feel it.
Have material, count, and which way the bad openings face. Ask how a sill sheds water when the wall above it is masonry or a clinging siding. Ask who patches trim. Steps and grade can make a simple replacement awkward on the downhill face. Say that. Odd sizes are normal in this older stock. One clear description of the worst sill is the right way to open the call.
These are not flat-street row windows over a stoop. Windows in Pittsburgh are openings on a slope, some of them half underground. Call the number on this page.