What Cool Roofing Can and Cannot Do Content
Below is what reflectivity genuinely does, what it cannot do on its own, and why we will give you rated figures but not a savings percentage.
What It Does
A reflective roof surface absorbs less solar radiation than a dark one. That's measurable and not in dispute, expressed through solar reflectance and thermal emittance ratings.
Less absorbed heat means a lower roof surface temperature. That can reduce heat transfer into the building and reduce thermal stress on the roof assembly itself.
What It Cannot Do
It can't tell you what your utility bill will be.
Your cooling costs depend on insulation levels, attic ventilation, duct location and condition, air sealing, HVAC efficiency and age, window area and shading, occupancy patterns, thermostat behavior, and the weather. The roof surface is one input into a system with many.
A house with leaky ducts in an unconditioned attic will not be rescued by a reflective roof. Fixing the ducts might do considerably more.
How to Evaluate a Cool-Roof Claim
Ask what the product's rated reflectance and emittance are, and whether those figures come from a recognized rating body or from the manufacturer's marketing.
Then ask how a quoted saving was calculated, and for what building. If the answer involves a percentage with no building-specific basis, treat it as marketing rather than engineering.
Where It Genuinely Makes Sense
On a low-slope roof already due for recoating, choosing a reflective product is a sensible decision, because you're doing the work anyway. On a commercial building with substantial roof area relative to volume, the effect is more pronounced than on a two-story house with a small roof footprint.
It also isn't only about energy. Lower surface temperatures reduce thermal cycling on the assembly, which is a durability argument independent of any utility question.
One Question That Sorts It Out
Ask how a quoted saving was calculated and for what building. A specific answer referencing your insulation, ducts, and roof area is engineering. A percentage with no building-specific basis is marketing, and it's worth knowing which you're being given.
Our Position
We'll tell you a product's rated properties and whether your roof is a candidate. We won't quote a savings figure, because we'd be making it up. See roof coatings and cool roofing.
Frequently Asked Questions:
Will a cool roof lower my electricity bill?
It may contribute, but the size of any effect depends on insulation, duct condition and location, air sealing, HVAC efficiency, shading, and how you use the building. The roof is one factor among several, and in many homes it isn't the largest one. We won't quote a savings figure because nobody can predict it honestly from the roof alone.
Do cool roofs work on tile and shingle roofs?
Reflective products exist for various roof types, including shingles with reflective granules. The coatings used to create cool roofs on low-slope systems aren't appropriate for tile or shingle roofs. What's suitable depends on your existing system, and applying the wrong product causes problems rather than solving them.
Is a cool roof required by code in Arizona?
Requirements vary by jurisdiction and by building type, and commercial energy codes address roof reflectance in some circumstances. Residential requirements differ from commercial ones. Your local building department or a design professional can confirm what applies to your specific project.
How long does reflectivity last?
Reflectance declines over time as surfaces accumulate dirt and weather, with most of the decline typically occurring in the early years. Some products are rated for both initial and aged reflectance, and the aged figure is the more useful one. Cleaning can recover some performance depending on the product and the surface.
See what we can document, or send us the letter. Or call (480) 565-7663.
