What is the proper way to prepare an Ottawa sunroom with condensation issues for painting?

Sunroom condensation must be eliminated before any painting begins, or the new paint will fail within months. In Ottawa's climate, sunrooms are particularly vulnerable to moisture problems due to extreme temperature swings and the large glass surface area that creates thermal bridging and condensation points.

The preparation process starts with identifying and fixing the moisture source. Check all window seals, door weatherstripping, and any gaps where the sunroom connects to the main house. Ottawa's freeze-thaw cycles can open up cracks that weren't visible during construction. Install or improve ventilation — many Ottawa sunrooms lack adequate air circulation, especially those built as three-season additions. A bathroom exhaust fan rated for the square footage can help, but it needs to vent outside, not into the attic or basement. Consider a dehumidifier during humid summer months when condensation is worst.

Once moisture is controlled, remove any existing paint that's peeling, bubbling, or showing water damage. Sand these areas down to bare substrate and clean thoroughly with TSP (trisodium phosphate) solution to remove any mildew or residue. Prime all bare areas with a high-quality stain-blocking primer like Kilz Original or Benjamin Moore Fresh Start — these products seal against moisture and prevent bleed-through. For previously painted surfaces in good condition, clean with mild detergent and allow to dry completely.

Critical timing consideration: Never paint a sunroom during Ottawa's spring thaw (March through early May) when humidity spikes and temperature swings are most extreme. Late May through September offers the most stable conditions. Use a moisture meter to verify surfaces are below 15% moisture content before priming.

If condensation issues persist despite your efforts, consider having the Ottawa Construction Network directory connect you with a painting contractor who has experience with sunroom moisture problems — they often recommend specific primer-paint systems designed for high-humidity environments.