A cool roof is a surface-performance choice.

Solar reflectance measures the fraction of incoming sunlight reflected by the surface. Thermal emittance describes how effectively the surface releases thermal radiation. The DOE guide explains both on a scale from zero to one. Neither number is the roof’s insulation value.

The CRRC explanation of SRI describes a calculated surface-temperature comparison under standardized conditions. SRI is an index, not a percentage; it can fall outside a zero-to-100 range. Record the value actually requested by a project specification rather than substituting a different metric.

Cool options exist within several roof families. EPA lists reflective membranes and coatings for low slopes and options including shingles, tile and metal for steeper roofs. Choose an appropriate roof assembly first, then compare available surfaces. “Cool” alone does not establish slope suitability, water resistance or attachment requirements. EPA’s product overview explains the range.

Have the bidder identify the exact manufacturer, product, color and rating record. The CRRC rating process distinguishes initial and aged properties. Confirm which are available and which the project requires. Save the record with the proposal so a later color substitution can be checked against it.

For example, imagine product A has a quoted initial reflectance of 0.70 and product B has an aged reflectance of 0.60. Those invented numbers do not establish which retains more reflectance after exposure. Obtain comparable initial and aged records before ranking them. Then compare other requirements separately.

DOE describes stronger cooling benefits in warm and hot climates, alongside a possible winter heating penalty. The outcome depends on building characteristics as well as weather. EPA also identifies insulation, building design and winter snow cover as factors affecting that penalty. A claim about roof-surface temperature should therefore remain a surface-temperature claim.

For an energy comparison, ask what building, insulation level, heating system, cooling schedule and utility rates were modeled. Request annual heating and cooling changes separately. If the proposal supplies only a percentage, ask “a percentage of what?” Cooling electricity is a different denominator from the entire household energy bill.

Comfort or reducing neighborhood heat may still matter even when a simple bill-payback calculation is modest. Write those goals down separately so the decision does not depend on a savings figure the proposal has not established.

A coating proposal needs to explain substrate condition, preparation, compatibility and treatment of defects before discussing reflectance. Ask what happens to existing warranty coverage and what inspections support the coating scope. A reflective finish is not evidence that wet materials beneath it have been addressed.

Include the manufacturer’s cleaning and maintenance requirements in the comparison; EPA notes that upkeep can help maintain reflectance. Obtain the expected maintenance tasks and their cost basis instead of assuming a roof stays at its initial rating without attention.

Finish your shortlist with the same roof scope, the exact product ratings and a separate energy estimate where useful. Continue with residential low-slope systems or asphalt shingles to check the underlying material decision.