Start with named products, not a generic ranking
Acrylic and silicone identify families of materials, not complete roof specifications. To make the comparison auditable, we examined Gaco A48 acrylic data, revised April 2024, and the Gaco S20/SPF specification, revised May 2026. This is a two-document comparison, not a market-wide test or a claim that Score offers either particular system.
| Question | A48 document | S20/SPF document |
|---|---|---|
| Volume solids | 54% | 95% |
| Water exposure | Not intended for surfaces prone to standing water; states a minimum drainage slope | Use the full system and applicable warranty; do not infer that drainage defects are acceptable |
| Existing silicone | Explicitly says not to apply over existing silicone coatings | Compatibility and preparation must be established for the actual substrate |
| Reflectance reporting | “After soiling” values carry a CRRC Rapid Rating footnote | Reports initial and after-soiling values; the excerpt does not establish an identical exposure protocol |
The equal-gallons comparison that can mislead an owner
Our calculation: one US gallon spread uniformly over 100 square feet produces about 16.04 wet mils: 231 cubic inches ÷ 14,400 square inches × 1,000. At 54% volume solids, theoretical dry film is about 8.7 mils; at 95%, about 15.2 mils. At this equal wet volume, the second theoretical film is about 1.76 times as thick.
This does not establish that either product should be installed at that rate. It excludes waste, texture, absorption, application tolerances, and system-specific minimums. It also says nothing by itself about durability. Its value is exposing why “same number of buckets” is not an equivalent scope.
Do not turn reflectance numbers into a false league table
The A48 sheet labels its after-soiling values as CRRC Rapid Rating. A number labeled “aged” or “after soiling” elsewhere may reflect a different procedure. Unless exposure method, colour, specimen, and test basis match, a side-by-side numerical ranking can imply comparability that has not been established.
For a defensible comparison, request the applicable rating entry, product identity, and test basis. Reflectance is not R-value, and a reflectance difference is not a predicted percentage reduction in the building’s energy bill.
Use a sequence of decisions
- Identify the existing coating and confirm compatibility.
- Resolve drainage and substrate suitability.
- Compare the required dry-film specification and verification method.
- Check the application window and future renewal requirements.
- Read the offered warranty’s coverage and exclusions.
The coating-candidate guide addresses whether restoration is appropriate. The warranty comparison explains why a silicone ponding exception in one sample form does not waive other conditions. For a project scope, see commercial roof coatings and SPF recoating.