Do I need heritage approval to add interior storm windows for soundproofing in the ByWard Market district?

Interior storm windows for soundproofing in the ByWard Market Heritage Conservation District generally do not require heritage approval because they are interior modifications that do not alter the exterior appearance of the building. Ottawa's Heritage Conservation Districts — and the ByWard Market is one of the most prominent — primarily regulate changes to the exterior character of designated properties. Adding a secondary glazing panel or interior storm window on the inside of your existing windows is typically considered an interior alteration that falls outside the scope of heritage review. However, the specifics matter, and there are situations where you should confirm with the City before proceeding.The ByWard Market Heritage Conservation District has a heritage conservation district plan that guides what types of changes are permitted and which require a Heritage Permit under Part IV of the Ontario Heritage Act. Exterior modifications — including replacing windows, changing window sizes, adding exterior storm windows with visible frames, or altering the streetscape appearance — require review and approval. Interior storm windows, by contrast, are installed entirely inside the existing window frame. Products like Indow window inserts, Magnetite magnetic panels, or custom acrylic secondary glazing panels sit inside the window opening, held in place by magnetic strips, compression tubing, or spring clips. They are completely removable and leave no permanent marks on the heritage window — which is exactly why heritage authorities generally have no issue with them.Practical Soundproofing Performance and CostInterior storm windows are one of the most effective soundproofing upgrades for Ottawa heritage properties where replacing the original windows is not permitted or desirable. A well-fitted interior storm window with a proper air seal creates an air gap of 2–4 inches between the existing window and the new panel, which can improve the window's sound reduction by 15–25 STC points. For a ByWard Market property facing the noise of Rideau Street traffic, George Street nightlife, or loading zones, this improvement is transformative. Custom interior storm windows typically cost $250–$600 per window depending on size and the type of glazing used, with laminated glass providing the best acoustic performance and acrylic panels offering a more budget-friendly option.There is one scenario where you should check with the City's heritage planning staff before proceeding: if the interior storm windows would be visible from the exterior — for example, if they change the apparent colour or reflectivity of the glass as seen from the street. This is unlikely with clear glass or acrylic panels, but tinted or frosted options could raise questions. A quick call to Ottawa's heritage planning department through 3-1-1 can confirm whether your specific installation needs any review. For heritage property owners dealing with noise issues, interior storm windows offer an excellent balance of acoustic performance, reversibility, and respect for the building's character. If you want professional guidance on the best product and installation approach for your specific ByWard Market property, the Ottawa Contractor Directory can connect you with window and soundproofing specialists familiar with heritage buildings in the area.Looking for experienced contractors? The Ottawa Construction Network connects homeowners with qualified professionals:613BinsRenoMotion Inc.ART DRYWALL AMD PAINTINGPure Flow Water Solutions inc.Diamond renovationsView all contractors →