ATTIC RAIN

Understanding Attic Rain: Causes, Risks, and Prevention

Attic rain occurs when warm, moist air inside your home enters the attic space and condenses on cold surfaces, such as the underside of the roof sheathing. During cold weather, this condensation freezes. The frozen condensation melts when the weather warms up, creating water droplets that can seep into insulation, wood framing, and drywall.

This phenomenon can occur for years before it is discovered. We have had listings where the homeowner was unaware of any issues until the buyer’s inspector looked into the attic.

The effects of attic rain can cause significant damage and cost 10’s of thousands to remediate. Prolonged moisture exposure can lead to wood rot, warping, and weakening of the roof’s structural components. 

Moisture creates an ideal environment for mould and mildew to thrive. Mould also poses serious health risks, including respiratory issues and allergic reactions. 

Wet insulation loses effectiveness, reducing energy efficiency and increasing heating and cooling costs. Water from attic rain can seep into ceilings and walls, causing stains, peeling paint, and damage to drywall.

Pete from Reid’s Roofing and Insulation says that homeowners seeking to improve their homes can unknowingly cause or exacerbate attic rain. They may wrap their exterior walls or get newer windows to eliminate drafts and save on utility costs. Sealing the exterior walls may force more warm, moist air into the attic.

Pete says that ventilation systems, such as soffit and ridge vents, can help, but they are often insufficient in our climate. Little or no wind blows during our cold winter nights so that warm, moist air has nowhere to go and can become frost on the underside of the roof sheathing. 

The most important defence is a perfectly sealed vapour under the attic insulation. Warm, moist air typically escapes through small openings around attic penetrations, such as light fixtures, plumbing stacks, electrical wires, attic hatches, and exhaust fans.

Prevention is critical. Identify and seal gaps around attic penetrations using caulking or spray foam insulation. Common areas include chimneys, plumbing stacks, electrical wiring, and recessed lighting fixtures. Verify that all household appliances, such as bathroom fans, kitchen hoods, and dryers, vent directly outside and not into the attic space. Check ducts for leaks and ensure connections are secure.

You may want to hire a contractor. Many homeowners have been injured stepping through their ceiling drywall.

If you are replacing your attic insulation, spray foam can help create an excellent vapour barrier when installed properly. It is more expensive though. 

Be aware that bathroom and kitchen renovations can disrupt attic vapour barriers.

The other way to prevent attic rain is to manage the humidity in your home. Many home builders are no longer installing humidifiers in their homes. With new homes being sealed so well, the humidifier can cause excess humidity to the point where it causes mould and rot in the main living space, particularly with dripping moisture on the windows.

Activities such as cooking, showering, and drying clothes increase indoor humidity, which can migrate into the attic if not adequately controlled.

Many investors will install bathroom vents with timers in their rental properties to help ensure moisture exits the home. They will also check that the exhaust systems have not come disconnected.

Use exhaust fans in kitchens and bathrooms to remove excess moisture during cooking and showering. Ensure that your home’s HVAC system appropriately manages air circulation and humidity. 

Dejan from Access Inspections recommends that homeowners keep humidity below 30% in the winter. He also says that when it is below -25 degrees Celsius, try to get closer to 20% humidity. If you have hardwood floors, wood finishings, and furniture, shoot for 25% to 30% humidity. 

The lower the temperature outside, the higher the dew point. The dew point is when moisture is released from the air. That is why we get moisture and frost on our vehicles when the temperature is lower.

Installing a humidity monitor in the attic can help you track moisture levels. There is, however, a downside to that, as there are many variables. Access Inspections and Reid’s Roofing and Insulation say the best prevention is regularly inspecting your attic, especially during very cold weather, for signs of frost, water stains, or wet insulation.

Attic rain can also occur in a brand-new home. Humans are not perfect, and there could have been an oversight with the attic contractors. Never assume the vapour barrier is good.

If you discover signs of attic rain, it is essential to act quickly.

Attic rain may seem like a minor issue, but its effects can be severe and far-reaching. By understanding its causes and taking proactive measures, homeowners can protect their attics from moisture damage, maintain energy efficiency, and avoid costly repairs. 

Prevention is always better than cure, so invest in the proper vapour barrier, insulation, ventilation, and moisture control to keep your attic and home in excellent condition.

Dennis Faulkner, B.A. Economics, works as a REALTOR® at MaxWell Challenge Realty. He can be contacted to answer your real estate questions at dennis.faulkner@icloud.com