Cool Roof & Reflective Coatings
A cool roof coating is a white, high-reflectance fluid-applied top coat that sends most of the summer sun back off a low-slope roof instead of into the building. It suits flat-roofed commercial, multifamily, and shop buildings along the Wasatch Front, and Grandview scopes and installs it under a Utah B100 general contractor license.
When a reflective coating is the right retrofit
A cool roof coating earns its place when the roof surface itself is the heat problem. A dark modified-bitumen or aged EPDM membrane can run 50 to 80°F hotter than the air on a July afternoon. That heat conducts through a thin roof assembly into the top floor, and any rooftop HVAC unit breathes the oven directly above the building.
It is a narrower tool than its siblings. An under-insulated attic wants insulation and air sealing, which pays back in every season. A failing assembly — wet insulation, soft sheathing, open flashing — is a job for building envelope improvements. A worn-out membrane belongs with our commercial roof restoration system; this page is the energy case for making that surface reflective when you do.
Steep-slope shingle roofs are the exception: coatings don’t belong on them. Cool-rated shingles and factory-finished standing seam metal do the same job there, as part of a replacement.
What “cool” means on the spec sheet
Two numbers decide whether a coating is a cool roof or just a white one. Solar reflectance is the share of sunlight bounced away — a fresh white silicone or acrylic coating tests around 0.80 or higher, against roughly 0.05 to 0.15 for black EPDM or granulated modified bitumen. Thermal emittance is how readily the surface sheds the heat it does absorb; most coatings sit near 0.85. The Department of Energy’s cool-roof guidance explains plainly what those values mean in use.
Specify the aged value, not the initial one. Three years of Wasatch Front dust, inversion grime, and canyon-wind debris pull a white roof’s reflectance down — typically into the 0.55 to 0.70 range — so the spec should assume the aged figure. A rinse each spring recovers a good share of it. Elevation cuts the other way: at 4,500 feet and up, UV is harsher than sea-level product literature assumes, and a surface that reflects it ages more slowly.
How a cool roof coating goes on
- Confirm the roof is a candidate. A moisture check, confirmed with a core cut where needed. Wet insulation gets repaired or sectioned out first; a coating over it seals the water in.
- Choose the chemistry for the roof. Silicone where snowmelt ponds behind a frozen drain in February; acrylic where the roof drains well and budget matters. Either way the top coat is bright white, since reflectance is the point.
- Prep that protects the reflectance. Power washing, three-course reinforcement on seams and penetrations, and a primer matched to the substrate. Rust and asphalt bleed-through turn a white roof tan within a year; a bleed-blocking primer prevents it.
- Apply to the thickness the rating assumes. Reflectance is tested at a specified dry-film thickness, and a thin coat neither performs nor lasts. We gauge wet film as we go and keep the readings.
- Document it. Listed aged reflectance, applied thickness, and photos go in your file — what a rebate-qualifying upgrade needs if a program applies.
Does a cool roof help in a Utah winter?
There is a small winter penalty, and we’d rather say so. A white roof absorbs less of the low winter sun. On the Wasatch Front the effect is minor: winter sun is weak and brief, and snow cover makes every roof white for weeks anyway. For a building with real summer cooling loads, the summer savings outweigh it.
Where it doesn’t pencil out is a well-insulated house with a vented attic and a steep roof. The attic buffers the living space, and the coating’s effect barely reaches the thermostat. Insulation or a high-efficiency HVAC upgrade does more for that house, and we’ll say so.
What does a cool roof coating cost in Utah?
As a ballpark planning number, a reflective coating on a sound low-slope roof in Utah County or Salt Lake County typically runs about $2 to $5 per square foot, acrylic low and silicone high, including cleaning, seam reinforcement, primer, and coats to the rated thickness. Planning figures, not a quote.
- Roof condition. Wet areas are cut out and infilled before coating, and that line can outgrow the coating itself.
- Penetrations and equipment. Forty curbs and pipe boots cost more to detail than four on a roof twice the size.
- Warranty length. Longer warranties are written in thicker dry mils, which is to say more gallons.
Sequence matters here as much as anywhere in an energy retrofit. Coat before replacing a rooftop unit, so the new equipment is sized for the lower load. If panels are coming, scope the solar-ready retrofit with the coating. Utility incentives for reflective roofing change year to year; we verify what’s current when we scope rather than promising a rebate. This scope sits within our wider specialty capabilities, and our license is verifiable through Utah DOPL.
Questions we actually get
Can you paint my shingle roof white to make it a cool roof?
No. Shingles are made to overlap and shed; a continuous film on top traps moisture, voids most shingle warranties, and peels. For a cooler steep-slope roof, cool-rated shingles or light-colored standing seam metal are the honest options, both as part of a replacement.
How much cooler does the building actually get?
The roof surface typically drops 50°F or more at peak afternoon compared with a dark membrane. How much reaches the rooms depends on what sits between roof and ceiling: a thin commercial deck with rooftop units feels it plainly; a house with a deep insulated attic may notice very little.
Will a white roof stay white along the Wasatch Front?
Not entirely. Dust, inversion-season grime, and canyon-wind debris dull it, which is why aged reflectance is the number that matters. A low-pressure rinse each spring restores much of it.
Can a cool roof coating go on under a future solar array?
Yes — coating first, racking second. A reflective surface under the panels keeps the air around them a little cooler, which helps output slightly,. We place walk pads along the planned rack lines and coordinate structural prep through the solar-ready scope.
Tell us what your roof is doing in July
Send the roof type, its age, and a note on what’s mounted up there. We reply within a couple of hours during business hours, a day at most, with a straight read on whether a reflective coating will pay you back.