Attic rain is a news worthy topic in Calgary, Alberta during the winter months and for good reason. It is more common than homeowners realize and often goes undetected until water is found in light fixtures or damage is visible on the ceiling. It is important for homeowners to understand what causes attic rain and what steps can be done to minimize frost buildup in the attic.
What Causes Attic Rain?
Attic rain occurs when warm, humid air from inside the home becomes trapped in the attic and freezes to the underside of the roof deck due to the cold temperatures outside. Attic rain is more common during long stretches of frigid temperatures because frost continues to build up until the temperature outside warms up enough to allow the frost to melt. This could result in a couple of weeks of frost build-up which may all melt at the same time depending on the temperature swing.
Why is it Called Attic Rain?
When the temperatures outside start to warm up, the frost in the attic starts to melt and in extreme cases it starts to “rain” from the ceiling. In less extreme (and more common) cases, homeowners start to find water in and around light fixtures mounted to the ceiling and water damage on the walls and floors.
Can Attic Rain be Prevented?
Attic rain may not be 100% preventable depending on the duration of the cold snap and building codes of your home (i.e. – vented soffit limitations), but it can be minimized by taking the following steps:
- Ensure your bathroom fan and dryer vent are properly venting outside the home
- Run bathroom fans during and after a shower for a minimum of 15 minutes and use hood vents when cooking
- Control the humidity in your home and ensure it isn’t too high in the winter months
- Have your attic and roof inspected to ensure it has adequate insulation and balanced ventilation
- Ensure roof vents are not blocked by snow