Acrylic Elastomeric Roof Coatings: White Reflective Roof Systems

What Is Acrylic Elastomeric Coating and How Does It Work?

It is a water-based coating built on flexible (elastomeric) acrylic polymers with white reflective pigments such as titanium dioxide and mineral fillers. It is applied as a liquid by roller or spray; the water evaporates and the polymer particles coalesce into a continuous, rubber-like flexible film. That is why the Saudi market calls it «rubber insulation» or «white insulation».

The coating works through two mechanisms: solar reflectance, the share of sunlight bounced off the surface, and thermal emittance, the surface's ability to radiate away the heat it has absorbed. U.S. Department of Energy guidance notes that white roofs typically reflect 55–90% of sunlight while dark roofs absorb 90% or more, and that a cool roof can stay more than 28°C cooler than a dark roof under the same conditions.

The Solar Reflectance Index (SRI) and how it is measured

SRI is calculated under ASTM E1980 (external source via the Consumer Safety Center) from reflectance and emittance together, on a scale where a reference black surface is 0 and a reference white surface is 100; good white coatings can exceed 100. Reflectance is measured by methods including ASTM C1549 (external source via the Consumer Safety Center) with a portable reflectometer. The Cool Roof Rating Council (CRRC) (external source via the Consumer Safety Center) publishes initial values and values after 3 years of outdoor exposure, without setting a minimum; minimums are set by codes and programmes.

Recommended Uses: Where It Fits and Where It Does Not

Advantages and Technical Properties

• Lower roof surface temperature and less heat transferred to the top floor; savings are an estimate and depend on the building.
• A continuous flexible film that seals hairline cracks and shields the roof from UV.
• Water-based, easy to apply, maintain and recoat over a sound existing layer.
• Lightweight, adding negligible load to the roof.

Disadvantages and Cautions

• Dust lowers reflectance: in dusty areas reflectance falls faster. U.S. Department of Energy guidance notes cleaning can restore up to 90% of initial reflectance, but it is best scheduled as part of routine maintenance.
• Ponding water: not all acrylic coatings are designed to withstand ponding water, so check the product data sheet and correct falls and drainage points first.
• Surface temperature at application: some data sheets require deferring application if the surface exceeds 60°C, and prohibit application if rain, dew or fog is expected during drying.
• Thin film: the film is thinner than other membranes, and any shortfall in the application rate shortens life and resistance. Manufacturers' data sheets note that thicker films perform better.
• Not full thermal insulation: it reduces solar heat gain but adds little thermal resistance. For code requirements see the Saudi Building Code insulation guide and thermal insulation.

Standard Application Steps and Testing

1. 1

   Inspection

   Check cracks, hollow tiles, drainage points and ponding areas, measure trapped moisture, and identify what needs leak detection or repair before coating.

2. 2

   Cleaning

   Pressure-wash the roof and remove dust, algae and flaking paint, then let the surface dry completely.

3. 3

   Crack and joint treatment

   Open cracks and fill them with a compatible sealant, then reinforce cracks, joints, corners and drain outlets with polyester fabric between two heavy coats of coating or sealant, as the system requires.

4. 4

   Primer

   Apply the system primer on porous concrete, tiles or aged surfaces to improve adhesion, as the manufacturer recommends.

5. 5

   First coat

   Apply the coat at the specified consumption rate, tracking the quantity used per area.

6. 6

   Second coat, perpendicular

   Once the first coat is dry, apply the second in a perpendicular direction to ensure full coverage and uniform thickness.

7. 7

   Inspection and handover

   Measure wet film thickness during work and reconcile total consumption, visually inspect for pinholes and thin areas, flood-test locally where needed, then hand over with a written warranty whose term depends on the insulation type and surface condition.

Climate Suitability by Saudi Region

Estimated Cost

A reflective coating on its own typically falls within the waterproofing range of SAR 18–40 per square metre, while an integrated roof insulation system combining thermal and waterproofing layers with a reflective finish typically ranges from SAR 45 to 85 per square metre. Prices exclude VAT, are indicative and are confirmed after inspection. They depend on roof condition, the length of cracks and joints needing reinforcement, the number of coats and the primer type. Try the cost calculator for an initial estimate.