Attic ventilation sizing calculator
An under-vented attic in Albuquerque hits 160 °F in July and shortens shingle life by 30%. Use the 1/300 rule to size intake + exhaust in seconds.
Without a vapor retarder, IRC R806.2 forces you to the 1/150 ratio (double the venting).
What we see on NM roofs every week.
The ridge short-circuits the boxes and you end up pulling air FROM the boxes down into the attic. Pick one exhaust type.
Exhaust without intake is the #1 attic problem in ABQ. Vent stack pulls conditioned air out of the house instead of hot air out of the attic.
Every re-paint we inspect has 20–40% of soffit NFA blocked with latex. Poke every hole open with a pick.
Slightly more intake than exhaust is ideal — it pressurizes the attic and blocks wind-driven rain intrusion at the ridge.
Insulation blocking the eave is the same as no soffit vents. Foam or cardboard baffles keep the path open.
Recessed cans, bath fans, and top-plate gaps dump humid house air into the attic — no amount of venting fixes that.
A 160°F attic eats shingles for lunch.
Under-vented attic? We fix it during any re-roof at no extra labor.
Book the free on-site inspection, or send a photo and we'll tell you what to do next. No sales pitch — we don't install roofs.