Roof Ventilation
The Hidden Half Of Your Roof
Ventilation quietly decides how long shingles live, whether ice dams form, whether attic mold grows, and what July costs to cool. Here’s the whole system — and how to fix a broken one.
Air In Low, Air Out High, Nothing In Between
Working ventilation is a loop: outside air enters at soffit intake, sweeps the underside of the roof deck, and exits at ridge or high exhaust — continuously, passively, forever. Every failure is a break in that loop: painted-shut or insulation-blocked soffits, exhaust with no intake to feed it, mixed vent types short-circuiting each other, bath fans dumping moisture mid-loop. Energy.gov explains the physics; we find your break and fix it.
What Bad Ventilation Actually Costs
Summer: superheated attics cook shingles from beneath, aging them years early and loading your AC. Winter: moist house air condenses on cold sheathing — hello attic mold — while trapped heat melts roof snow into ice dams. One hidden system, four expensive symptoms. The assessment is free and the fixes are usually modest: baffles, cleared intake, correct exhaust.
Real Questions From Real Roofs
How do I know if my ventilation is bad?
Symptoms talk: an attic you can feel from the hallway in summer, frost on sheathing in winter, ice dams, mold spotting, or shingles aging fast on an under-20 roof.
Can more insulation replace ventilation?
No — they solve different problems and need each other. Insulation without airflow just moves the condensation point; the loop still has to breathe.
Is a powered attic fan a good fix?
Usually not the first one — powered fans can depressurize attics and pull conditioned air up through the ceiling. Passive balance nearly always wins; we will tell you the exceptions.
What is the 1/300 rule for attic ventilation?
The common code baseline: one square foot of net vent area per 300 square feet of attic, split between intake and exhaust — the starting math we run for your actual attic.
Can too much ventilation be a problem?
Unbalanced ventilation can — exhaust exceeding intake pulls conditioned air from the house. Balance matters more than totals.
Does attic ventilation lower cooling bills?
Meaningfully — exhausting superheated attic air reduces the heat load pressing on your ceiling insulation all summer.
What are signs of poor attic ventilation?
A hallway ceiling warm to the touch in summer, frost on winter sheathing, ice dams, mold spotting, and shingles aging fast on a young roof.
Should soffit vents be blocked with insulation?
Never — that suffocates the whole loop. Baffles exist precisely to hold the airway open where insulation meets the eaves.
Ventilation Components
The parts of the loop.
Roof Aging Fast? Attic Telling Tales?
Free ventilation assessment — the loop, measured and mapped.