Attic Rain Facts and Do’s & Don’ts | Avalon Master Builder

Attic Rain

Facts and Do’s & Don’ts

Published on: February 23, 2024

What is Attic Rain?

Attic Rain is melted frost that accumulates during sustained cold, and drips down faster than it can evaporate.

Why Does Attic Rain Happen?

Attic Rain happens when frost from a very cold period does not have enough time to evaporate and escape through the attic vents. Typically, this happens in a period of prolonged frigid cold and then rapid warming. The extra moisture falls to the insulation between the attic and inside ceiling and can move downward toward the air and vapour barrier. Sometimes, water makes its way into the home and can appear as wet marks on the ceiling or beyond.

Can the Chance of Having Attic Rain Lessen?

Avalon works to have a continuous air and vapor barrier throughout the home to stop moist air from entering the attic from the home, however, it is impossible for this barrier to be 100% sealed. This means moist air can get into the attic, but there are things homeowners can do to reduce frost buildup in attics.

Do’s & Don’ts:  What homeowners can do to reduce Attic Rain

  • Do lower the Heat Recovery Ventilator (HRV) relative humidity setting to 20% during periods of extreme cold.
  • Do always have the HRV ON and set at 20/40 (This means it runs a minimum of 20 minutes per hour to ensure your air is fresh)
  • Do always use the hood fan when cooking.
  • Do always set your HRV bathroom fan to 60 minutes before getting in the shower or bathing.
  • Do always turn your humidifier off (if you have one) during cold snaps. (In airtight homes like your Avalon home, a humidifier is rarely needed)
  • Do leave any spots that appear to dry naturally.
  • Do Not disturb the ceiling around the Attic Rain spots.

What to do next: Attic Rain

If attic rain spots are taking a long time to dry or have left a stain on the ceiling, please use the Service and Warranty QR code below to submit a service ticket. Don’t forget to include pictures.

Periodically, Attic Rain can present more seriously. If this happens in your home, please immediately submit a service ticket.

More Questions or Concerns?

If you have any additional questions about this topic, please reach out to us at

Reference Material: Attic Rain, Alberta New Home Warranty Program

Use the QR code below to enter a service ticket from a smartphone or click on the QR code from a tablet, laptop or desktop computer, opening a new window to submit a service request.