Window replacement costs in Portland

In a Portland historic district, the zoning code has a say about your windows. Exterior alterations there go through historic resource review unless the code exempts them, and window replacement has its own narrow exemptions.

Replacing vinyl, fiberglass or aluminum windows on a contributing house skips review when the house was built before 1940, the new windows are wood or metal-clad wood, they fit exactly in the existing openings, and the glass sits at least two inches back from the outside face of the siding. In single-dwelling zones there's a second pass for windows that face the rear lot line. Fiberglass is allowed there too, under the same fit and glass-depth rules.

The building side is simpler. Portland Permitting & Development says you don't need a permit to replace a window when the header keeps its size and location and the clear opening doesn't shrink. Widening one does take a permit, and the city notes land use review may apply in a design or historic zone.

Whatever the zone, a replacement window in an existing Portland house needs a U-factor of 0.30 or lower.