Why does my house feel colder after window replacement?

Your house likely feels colder after window replacement due to reduced air leakage, changes in humidity levels, or installation issues that need addressing. While this seems counterintuitive, it's actually a common experience that usually resolves within a few weeks.

The most frequent cause is dramatically reduced air infiltration. Your old windows were likely leaking significant amounts of warm air, which your heating system compensated for by running more frequently. New, properly sealed windows eliminate these drafts, but your thermostat may need time to recalibrate. The house now retains heat more efficiently, but the heating system hasn't adjusted its cycles yet. This can create periods where the system isn't running as often, leading to temporary temperature drops.

Humidity changes also play a major role in thermal comfort. Leaky old windows allowed moisture to escape continuously, and your heating system worked harder to maintain temperature in that drier environment. New windows trap more humidity inside, which should actually make you feel warmer at the same temperature - but during the adjustment period, the changed air quality can feel different. In Toronto's winter climate, this humidity retention is typically beneficial once balanced.

Installation-related issues could also be the culprit. If the window installation wasn't properly air-sealed around the frames, you might have new drafts in different locations. The Ontario Building Code requires proper vapor barriers and insulation around window openings, and gaps in this work create cold spots. Additionally, if the new windows have significantly different thermal properties than expected, or if they're not operating properly (not closing fully, damaged seals), they won't perform as designed.

Toronto's climate considerations make this adjustment period more noticeable. With our temperature swings from -20°C to +5°C in winter, your heating system needs to recalibrate for the new thermal envelope. The reduced air changes per hour means your furnace or boiler runs differently, and it can take 2-4 weeks for the system to find its new equilibrium.

Professional assessment is warranted if the cold feeling persists beyond a month. Have your installer return to check the installation quality, verify proper sealing, and ensure all windows operate correctly. A thermal imaging inspection can identify any installation gaps or thermal bridging issues. If the windows themselves are performing properly, consider having your HVAC system rebalanced for the new thermal conditions.

Next steps: Give the system 2-3 weeks to adjust while monitoring your energy bills. If you're still uncomfortable, contact your window installer to verify the installation meets Ontario Building Code requirements and manufacturer specifications. Document any specific cold spots or drafts to help with diagnosis.

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