Uploaded April 2026 | Updated September 2026, 3 weeks ago
Applying solar-reflective "cool roof" paint is one of the most effective DIY ways to lower indoor temperatures, especially in tropical climates like Jakarta where the sun is relentless.
00:23 Sensor monitoring
00:49 Clean
01:22 Compare Cool Roof and Standard Roof
02:55 Compare 2 Cool Roof
Here is a step-by-step guide to ensuring the application lasts and reflects the maximum amount of heat.
1. Preparation
The paint will only reflect heat effectively if it bonds perfectly to the surface.
Clean the Surface: Use a high-pressure washer or a stiff brush with water and mild detergent to remove moss, algae, dust, and loose debris.
Repair Leaks: Inspect for hairline cracks or rusted spots (if using metal roofing). Use a waterproof sealant or flashing tape to patch these before painting.
Dry Completely: Ensure the roof is bone-dry. Applying paint on a damp surface will lead to bubbling and peeling within months.
2. Priming
Depending on your roof material, a primer acts as the "glue" between the roof and the reflective coating.
For Metal/Galvanized: Use a rust-inhibitive primer to prevent corrosion from trapped moisture.
For Concrete/Clay Tiles: Use a masonry sealer or a dedicated multi-surface primer to reduce the porosity of the tiles.
For Asbestos/Fiber Cement Sheets: Use a Water-Based Acrylic Sealer or a High-Adhesion Masonry Primer.
Dust Binding: Asbestos surfaces tend to become "chalky" or dusty over time. A primer binds these loose particles so the topcoat doesn't peel off.
Sealing Porosity: Asbestos is highly porous. A primer seals these pores, preventing the expensive cool roof paint from being soaked up like a sponge, which ensures a uniform reflective film.
Never sand or dry-brush asbestos sheets. This releases hazardous fibers into the air. Always dampen the surface before cleaning and use low-pressure water to remove grime before applying your primer.
3. Application Process
Cool roof paint is usually thicker than standard house paint (often elastomeric), so it requires specific handling.
Check the Weather: Ensure no rain is forecasted for at least 24 to 48 hours.
Temperature Timing: Start early in the morning once the dew has evaporated but before the roof becomes too hot to touch. If the surface is too hot, the paint will dry too fast and won't level correctly.
First Coat: Apply a generous first layer using a long-nap roller or a professional airless sprayer. Work in small sections to ensure even coverage.
Second Coat: Always apply at least two coats. Apply the second coat perpendicular to the first (cross-hatching) to ensure no pinholes are left exposed.
Technical Details for Cool Roof Effectiveness
1. Solar Reflectance Index (SRI) & TSR
For maximum cooling, choose a coating with a high Total Solar Reflectance (TSR), ideally 80% or higher. The goal is to bounce solar radiation back into the atmosphere before it converts into heat. High-gloss white is typically the most effective color.
2. Application Thickness (Dry Film Thickness)
Do not apply the paint too thinly. Reflective pigments require a specific density to function:
Minimum 2 Coats: Apply at least two coats using a "cross-hatch" method (first coat horizontal, second coat vertical).
Film Build: Follow the manufacturer’s specs for micron thickness. A thicker layer not only reflects heat better but also provides better waterproofing for the fragile asbestos sheets.
3. Thermal Emittance
An effective cool roof must also have high Thermal Emittance (typically bigger than 0.80). While reflectance bounces light away, emittance allows the roof to "shed" any heat that was already absorbed, helping the building cool down faster in the evening.
4. Maintenance and Cleanliness
The effectiveness of a cool roof is directly tied to how clean it is.
Dirt Accumulation: Dust, soot, and algae growth on the asbestos surface will absorb heat and negate the cooling benefits.
Periodic Cleaning: Gently wash the roof once a year to maintain its "brightness" and ensure the reflective properties remain intact.
Applying solar-reflective "cool roof" paint is one of the most effective DIY ways to lower indoor temperatures, especially in tropical climates like Jakarta where the sun is relentless.
00:23 Sensor monitoring
00:49 Clean
01:22 Compare Cool Roof and Standard Roof
02:55 Compare 2 Cool Roof
Here is a step-by-step guide to ensuring the application lasts and reflects the maximum amount of heat.
1. Preparation
The paint will only reflect heat effectively if it bonds perfectly to the surface.
Clean the Surface: Use a high-pressure washer or a stiff brush with water and mild detergent to remove moss, algae, dust, and loose debris.
Repair Leaks: Inspect for hairline cracks or rusted spots (if using metal roofing). Use a waterproof sealant or flashing tape to patch these before painting.
Dry Completely: Ensure the roof is bone-dry. Applying paint on a damp surface will lead to bubbling and peeling within months.
2. Priming
Depending on your roof material, a primer acts as the "glue" between the roof and the reflective coating.
For Metal/Galvanized: Use a rust-inhibitive primer to prevent corrosion from trapped moisture.
For Concrete/Clay Tiles: Use a masonry sealer or a dedicated multi-surface primer to reduce the porosity of the tiles.
For Asbestos/Fiber Cement Sheets: Use a Water-Based Acrylic Sealer or a High-Adhesion Masonry Primer.
Dust Binding: Asbestos surfaces tend to become "chalky" or dusty over time. A primer binds these loose particles so the topcoat doesn't peel off.
Sealing Porosity: Asbestos is highly porous. A primer seals these pores, preventing the expensive cool roof paint from being soaked up like a sponge, which ensures a uniform reflective film.
Never sand or dry-brush asbestos sheets. This releases hazardous fibers into the air. Always dampen the surface before cleaning and use low-pressure water to remove grime before applying your primer.
3. Application Process
Cool roof paint is usually thicker than standard house paint (often elastomeric), so it requires specific handling.
Check the Weather: Ensure no rain is forecasted for at least 24 to 48 hours.
Temperature Timing: Start early in the morning once the dew has evaporated but before the roof becomes too hot to touch. If the surface is too hot, the paint will dry too fast and won't level correctly.
First Coat: Apply a generous first layer using a long-nap roller or a professional airless sprayer. Work in small sections to ensure even coverage.
Second Coat: Always apply at least two coats. Apply the second coat perpendicular to the first (cross-hatching) to ensure no pinholes are left exposed.
Technical Details for Cool Roof Effectiveness
1. Solar Reflectance Index (SRI) & TSR
For maximum cooling, choose a coating with a high Total Solar Reflectance (TSR), ideally 80% or higher. The goal is to bounce solar radiation back into the atmosphere before it converts into heat. High-gloss white is typically the most effective color.
2. Application Thickness (Dry Film Thickness)
Do not apply the paint too thinly. Reflective pigments require a specific density to function:
Minimum 2 Coats: Apply at least two coats using a "cross-hatch" method (first coat horizontal, second coat vertical).
Film Build: Follow the manufacturer’s specs for micron thickness. A thicker layer not only reflects heat better but also provides better waterproofing for the fragile asbestos sheets.
3. Thermal Emittance
An effective cool roof must also have high Thermal Emittance (typically bigger than 0.80). While reflectance bounces light away, emittance allows the roof to "shed" any heat that was already absorbed, helping the building cool down faster in the evening.
4. Maintenance and Cleanliness
The effectiveness of a cool roof is directly tied to how clean it is.
Dirt Accumulation: Dust, soot, and algae growth on the asbestos surface will absorb heat and negate the cooling benefits.
Periodic Cleaning: Gently wash the roof once a year to maintain its "brightness" and ensure the reflective properties remain intact.
