Hansberger Refrigeration Blog: Your AC Repair Resource

Why Does HVAC Condensation Happen in Cold Weather?

Winter is the season for issues with HVAC condensation. Moisture condenses on indoor surfaces more frequently in winter as humid indoor air heated by the furnace makes contact with colder surfaces. The most conspicuous evidence in winter is typically moisture forming on the inside of cold window panes and glass sliding doors, often causing streaking on the glass and mildew formation on adjacent wooden frames and sills. HVAC condensation may also occur on the interior side of exterior walls that are cooler than room temperature, causing peeling paint and staining.

The second element in HVAC condensation is high indoor humidity. It’s a more common issue today, as homes are being built more airtight for heating and cooling efficiency. This, however, produces the side effect of accumulating excess indoor water vapor. High humidity levels in the house originate from numerous causes, including:

  • Cooking on the stove and in the oven releases water vapor that raises the humidity level in the kitchen and nearby rooms.
  • Steamy hot water produced by bathing also contributes to indoor humidity.
  • Washing machines can be a source of humidity, as can driers that are not properly vented.
  • Water vapor is present inside the home in the breath of humans and pets. In an enclosed indoor environment during winter, this also contributes to higher humidity.

To reduce water vapor and the side effect of condensation on indoor surfaces in winter, keep indoor relative humidity levels at an average of 45%.

  • Install exhaust fans in the kitchen, bathrooms, and the laundry room.
  • After bathing, run the bathroom exhaust fan for at least 30 minutes.
  • Make sure the drier has a dedicated, fully intact duct pipe that conveys humid drier exhaust outside.
  • Upgrade single-pane windows to double-pane insulated glass. This prevents the interior side of the window from becoming excessively cold and triggering condensation.
  • Where indoor humidity remains an ongoing problem, consider installing a whole-house dehumidifier to continuously maintain humidity at precise settings.

Get more information about the causes and cures of indoor HVAC condensation in winter. Contact the pros at Hansberger Refrigeration and Electric Company.