Serving Salt Lake City, UT & Nearby Areas
(385) 438-3591
Serving Salt Lake City, UT & Nearby Areas
(385) 438-3591
If your AC runs all day and the top floor stays hot after sundown, look above the ceiling: an under-ventilated attic stores the day's heat and radiates it down all night. The hottest attic we ever measured was 180 degrees. Your attic should run within about 20 degrees of the outside air.
Measure your attic's temperature on a hot afternoon before you blame or replace the AC.
A ventilated attic sheds heat with the evening. An under-ventilated one radiates it into bedrooms all night.
Put a thermometer in the attic and compare it to outside.
In a Utah summer, check the attic before you blame the AC. If it's not within 20 degrees of outside, you found your heat.
Mattie Tueller, Master Roofing
The attic works like a heat battery. All day, Utah's sun charges it: the roof absorbs solar load and the attic air climbs far past the outdoor temperature. A ventilated attic discharges that heat with the evening air. An under-ventilated one has nowhere to send it. So it radiates the stored heat down through the ceiling into your bedrooms all night.
The hottest attic Master Roofing ever measured was 180 degrees. The working target is an attic within about 20 degrees of the outside air, so on a 95-degree day a healthy attic runs near 115 while a failed one can run 60 degrees hotter. Your air conditioner fights that radiant load from below. That's why it can run all day, lose all evening. Get blamed for a problem it never caused.
The timing tells on it. An undersized or failing AC struggles most at the afternoon peak. An attic problem keeps hurting after sundown, when the outside air has cooled but the stored heat keeps radiating.
The Department of Energy's guidance on attic ventilation describes exactly this mechanism. Most homeowners route the call to the AC company anyway. The AC company cannot fix a roof-system problem.
Because in Utah, most are: about 90 of 100 attics run under-ventilated. The causes stack up over a house's life.
And nobody catches it. That's because a roof can pass inspection without anyone measuring the ventilation ratio.
The fix is balanced airflow: intake at the eaves feeding exhaust at the ridge, sized to the code ratio for your attic's square footage. It is measurement-driven work, usually a retrofit, and it does not require a new roof.
Correcting the ventilation pays out beyond the summer:
One system, one fix, and half the house's mystery problems trace back to it.
By the time I get called about a hot upstairs, the family has usually spent a whole summer fighting it: thermostat wars, window units in the kids' rooms, an AC tech out twice who found nothing wrong. Everyone is staring at the machine. The attic is running the whole show.
An under-ventilated attic cooks your house like a phone book in the oven: the heat soaks in and keeps radiating long after the sun goes down. The hottest one Master Roofing ever measured was 180 degrees. No air conditioner on earth wins against that from below.
Sometimes the honest answer really is the AC, and the thermometer test sorts it in one afternoon: attic within about 20 degrees of outside, call the AC company with my blessing. Way past that, the roof system is your problem, and it is fixable without drama. This is what I mean when I say a roof is a service, not a product: the system above your ceiling either works for you every day or against you every night.
This article is general information about Utah roofs, not an assessment of yours. Every roof is different, and no article can tell you what is actually happening on your specific house. Have a licensed roofing contractor look at it in person before you act on anything here.
Usually not by itself, and sometimes it backfires. A powered fan without adequate intake pulls air from the easiest source available. That can be your conditioned house air through ceiling gaps. Balance comes first: intake at the eaves, exhaust at the ridge, sized to the ratio. Once the passive system is right, most attics never need the fan.
Yes, and measurably. The Department of Energy identifies attic heat as a direct load on home cooling: your AC runs longer to counter heat radiating through the ceiling, and the hotter the attic, the worse the math. A power bill that spikes every July while the upstairs stays uncomfortable is paying for the same problem twice.
Yes. New construction passes inspection without anyone measuring the net free vent area against the ratio. Builder-grade venting often installs the visible exhaust while shorting the intake. A new house with a hot top floor deserves the same thermometer test as an old one. The build date changes the odds a little; it does not change the physics.
It is aging your roof from underneath. Sustained attic heat cooks the asphalt in shingles from the back side. That shortens their life and shows up worst over vaulted ceilings. Manufacturers know it too: shingle warranties require code-compliant ventilation. The ratio is what gets checked when a claim is on the line. Comfort is just the symptom you can feel.
Within about 20 degrees of the outside air, measured at the hottest part of the afternoon. On a 95-degree day, a healthy attic runs near 115; a failing one can push 150 or more. One cheap thermometer and one hot afternoon give you the number. The number tells you whether the roof system or the AC deserves the call.
We're here to see what's going on with your roof. A real assessment starts with your history and your attic, not a number from the driveway. You'll get a straight answer about what's up there, what it needs, and what it costs. Sometimes the honest answer is: your roof looks great.