Solving Condensation in the Roof
Extreme rot over years and years of letting condensation and moisture go unchecked
Solving Condensation
Condensation becomes a problem in attic spaces because it can produce widespread water damage in a thaw cycle after a long cold spell. During freezing temperatures, the attic space stores built-up water vapor as frost from everyday living. During a warm-up cycle, the attic space will start dripping everywhere because of the state change of water from a solid to liquid. Sometimes, thicker insulation can absorb the water droplets. Sometimes the water droplets evaporate before soaking into the ceiling material. When extreme temperature swings happen, frequently, it cannot. The more frost that builds up translates to more water when it thaws. December of 2019 was condensation month. We had below zero temps followed by high temps right around Christmas. Many homes had issues.
Many factors can cause condensation on the underside of roof boards, plywood, or nails. Building practices now address how important getting water vapor out is. Homes built today are using closed-cell foam, vapor retarders, and products to quarantine water vapor. HVAC systems can manage water vapor when it's where it's supposed to be. When updating homes, these things are crucial and often not addressed.
Condensation is not particular to old homes but happens more frequently to any home with these characteristics: no vapor barriers, poor ventilation, and poor insulation. Following the steps below can help to solve condensation.
Items that solve condensation or slow it down
Make sure vapor barriers are intact- This will solve the most severe condensation issues. Without a vapor barrier, water vapor from everyday living has free reign in the home and can escape in the attic and cause problems.
Adding insulation to the attic - Make sure your home has a vapor barrier first and bring the insulation level to at least 15”. Blowing insulation like cellulose or fiberglass blown-in works best. This maybe isn’t a perfect solution but can slow down condensation
Buy the right insulation - Use the options above. Wrong insulation can amplify instead of solving condensation. Buying insulation with a vapor barrier already on it or polyurethane sheet foams can create multiple vapor barriers. This traps moisture between layers of your insulation.
Make sure soffit vents are open - This is the intake or eaves of the home. New homes have working soffits pre-1960 homes usually don’t. Adding insulation in the wrong areas can block the soffit vents which is the air intake of the home. Attic cross ventilation is necessary and will help exhaust water vapor which does solve condensation. Sometimes homeowners view air movement in the attic as a problem. Blocking soffits or air intakes will cause more of a problem with condensation.
Address Missing Insulation- Attic insulation can settle and actually misplace by wind or mechanical means. Exterior wall corners are prime areas. Rake insulation back to eliminate heat loss to solve condensation in these areas.
Address attic exhaust - Make sure box vents, ridge vents, gable vents, or power vents are getting air out of the attic space.
Ventilate bathroom and range fans properly - Absolutely critical to solving condensation. A bathroom fan venting into the soffit of a home, or worse yet just venting into the attic space will produce condensation. A hood range that vents into the attic are doing the same thing. Vents must terminate through sidewalls or the roof.
Keep your attic unconditioned if not a living space- Doing the items discussed above will automatically address this one. The attic temperature should be close to matching the outside air temperature. Unconditioned space is the terminology and it means no heat or cooling in that area. No extra heat is a great way to solve condensation
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