What's happening up there? The real story of roof ventilation

AAR Expert Wendy Marvin shares tips for properly addressing your home's ventilation needs.

After 20 years of inspecting homes, I've seen how poor roof ventilation can silently damage your biggest investment. Let me share what you need to know in plain talk. 

How your roof should work 

Think of your attic like lungs. It needs to: 

• Breathe in: Fresh air comes in through vents at your eaves or soffits (those overhangs around your roof edge) 
• Exhale out: Warm, moist air escapes through vents on or near your roof peak 
• The airways: Clear paths between these points 

When working properly, this system keeps your attic temperature reasonable and prevents moisture buildup.

The timeline of trouble 

Let me walk you through what I've seen happen to homes with poor ventilation, year by year. It's like watching the same movie play out in slow motion across thousands of homes. 

Year 1: Problems begin invisibly. Your attic overheats in summer (up to 160°F!), baking your shingles. In winter, warm house air meets cold roof surfaces, creating condensation that settles on wood and insulation. Warning signs? Slightly higher energy bills and occasional musty smells. 

Years 2-3: Moisture accumulates. Insulation gets damp and loses effectiveness. Mold finds those dark, damp corners. Your roof materials age faster than they should. You might notice that musty smell more often and see minor staining in the attic. 

Years 4-6: Damage accelerates. Mold colonies spread, wood begins deteriorating and roof sheathing softens. People in your home might experience more allergy symptoms as air quality suffers. 

Years 7-10: Serious problems emerge. Structural elements weaken, leading to sagging. Actual leaks develop, damaging your ceilings. Mold remediation becomes necessary. Energy bills climb significantly. 

Beyond 10 years: Major repairs become unavoidable, potentially costing tens of thousands of dollars. 

A simple prevention plan

• Check your ventilation: Make sure you have both intake vents (at the eaves) and exhaust vents (near the peak), with clear paths between them.  
• The right balance: You need about 1 square foot of ventilation for every 300 square feet of attic floor, with half as intake and half as exhaust.  
• Keep airways clear: Ensure insulation doesn't block soffit vents and remove stored items that obstruct airflow.  
• Direct moisture outside: Bathroom fans, kitchen vents and dryer exhausts should vent directly outside, never into the attic.  
• Regular inspections: Every 2-3 years, have a professional check your ventilation system or look yourself for signs of moisture. 

A real-life lesson

I worked with a family who discovered ceiling stains in their 12-year-old home. When we inspected, they had plenty of roof vents but almost no intake ventilation. We fixed it by adding proper soffit venting, installing baffles, replacing the damaged materials and taking care of the mold and insects. Total cost? Over $22,000. Installing proper ventilation during construction would have cost about $2,000.

Take action this week

1. Schedule a roof inspection if it's been more than 3 years 
2. Visit your attic with a flashlight to check for dark stains or dampness.
   1. Take note of the thickness of insulation and any bare spots to fix.
3. Verify all your bathroom and kitchen fans vent outside properly.
4. If you note any issues, have a Professional Roofer pop by for an inspection.

Remember, your home shelters you every day. Taking care of ventilation is how you return the favor – and save yourself from expensive repairs down the road.