Find the moisture first
Record whether moisture is on the room-side surface, the outside surface or between sealed panes. Photograph it at the time it appears and note the room, weather, coverings and activity in the house. These observations help a professional distinguish a surface-condensation pattern from a sealed-unit concern or a possible leak.
Look at the room as well as the window
Moist indoor air can condense on a cooler surface. Restricted airflow behind deep blinds, closed curtains or furniture can make conditions at the glass different from the rest of the room. Have indoor humidity, ventilation and the location of heat sources considered alongside frame and glazing performance. A replacement window alone is not a diagnosis of a moisture problem.
Keep leaks in the conversation
Water appearing after rain, staining at the head or sill, or deteriorating finishes should be assessed as possible water-entry evidence. Do not cover recurring staining with new trim without investigating the source. Ask the assessor to distinguish the glazing unit, frame joints, perimeter installation and adjoining wall as potential contributors.
Build an evidence-based request
Share photographs, when the problem began, whether it affects one room or the whole home, and whether it follows rain or everyday indoor activities. Avoid dismantling the window or blocking drainage openings to investigate. Ask for a written finding and a proposed remedy that explains which cause it addresses. Persistent moisture or visible damage deserves a qualified assessment.
Questions worth asking
- Which surface is wet?
- Does it follow rain, cold weather or indoor activity?
- Are coverings restricting airflow?
- Has the wall or frame been assessed for water entry?
Further reading
Natural Resources Canada: condensation ↗Source checked October 16, 2026. Current requirements and eligibility need separate project-specific verification. This guide is an original planning explanation, not a product certification or installation instruction.
