🚨 Cool Roof

Today Korean Social News for Beginners | 2025.08.23

0️⃣ Rooftop Heat-Reflective Paint Reduces Cooling Costs and Urban Heat Island Effect

📌 White Paint 'Cool Roof' on Rooftops…Reduces Summer Heat and Saves Electricity Bills

💬 Seoul City has expanded its 'Cool Roof' program to private homes to fight heat waves and save energy. This year, they applied heat-reflective paint to 20 low-income households in Seongdong District. The results show indoor temperatures dropped by 1-2 degrees and cooling electricity bills were greatly reduced, according to positive feedback from residents. Cool roof technology uses special paint with high sunlight reflection on building rooftops or roofs to reduce heat absorption. This technology is already widely used in the United States and Europe. Seoul City is also conducting test projects in apartment complexes to verify effectiveness, and this has important meaning for urban heat island reduction and greenhouse gas cuts as part of climate crisis response.

💡 Summary

• Cool roof is a technology that applies heat-reflective paint with high sunlight reflection to rooftops to lower indoor temperatures.
• Seoul City's project with 20 vulnerable households showed 1-2 degree indoor temperature reduction and cooling cost savings.
• Policy expansion is expected for urban heat island reduction and climate crisis response.

1️⃣ Definition

Cool Roof means an eco-friendly building technology that applies special heat-reflective paint or coating materials with high solar reflection to building rooftops or roofs to reduce heat absorption and lower indoor temperatures. 'Cool Roof' means 'cool roof', and unlike regular black roofs, it uses white or bright-colored reflective materials.

This technology reflects solar heat to block heat from entering the building interior, reducing summer cooling energy use and saving electricity bills while also lowering the temperature of the entire city. It is receiving attention as an eco-friendly adaptation technology for the climate change era.

💡 Why is this important?

• Provides natural cooling effects in an era where heat waves are becoming common.
• Contributes to electricity bill savings for individuals and energy conservation for society.
• Helps reduce urban heat island effects and lower overall city temperatures.
• A practical and economical solution for responding to the climate crisis.

2️⃣ Cool Roof Principles and Effects

📕 Solar Heat Reflection Principles

• The difference between regular roofs and cool roofs is clear. Key features are as follows:

  • Regular black asphalt roofs absorb 80-90% of solar heat, with surface temperatures reaching up to 80 degrees.
  • Cool roofs reflect 70-80% of solar heat, lowering roof surface temperature by 20-30 degrees.
  • The reflected heat is released into the atmosphere, greatly reducing heat transferred to the building interior.
  • This results in top-floor indoor temperatures dropping by about 1-5 degrees.

• Various cool roof materials and installation methods exist. Main types are as follows:

  • Reflective paint method is the most economical way of applying special coating to existing roofs.
  • Attaching reflective sheets or membranes has high durability and long-lasting effects.
  • Methods using white gravel or ceramic coating materials also exist.
  • Each method has different costs, effects, and durability, so choosing the right one for building characteristics is important.

📕 Actual Effects and Performance Data

• Domestic and international research results prove effectiveness. Main achievements are as follows:

  • According to U.S. Department of Energy research, cool roofs reduce annual cooling energy by 10-15%.
  • California's mandatory cool roof policy greatly reduced the state's overall energy consumption.
  • Domestically, Korea Institute of Energy Technology experiments confirmed 15-20% summer cooling cost reduction.
  • In Seoul City's Seongdong District pilot project, participating households actually experienced lower perceived temperatures and electricity bill savings.

• Social and environmental ripple effects are also significant. Main impacts are as follows:

  • City-wide adoption can reduce urban heat island effects by 2-5 degrees.
  • Reduces summer electricity demand surges, lowering blackout risks and contributing to power grid stability.
  • Can reduce greenhouse gas emissions by thousands of tons annually through cooling energy savings.
  • Especially for vulnerable groups, it helps solve energy poverty problems by reducing cooling cost burdens.

💡 Key Advantages and Considerations of Cool Roof

1. Cooling Cost Savings: 10-20% summer electricity bill reduction effect
2. Indoor Comfort Improvement: Top floor indoor temperature drops 1-5 degrees
3. Urban Heat Island Reduction: Effect of suppressing city-wide temperature rise
4. Eco-friendliness: Natural cooling effect without chemical refrigerants
5. Maintenance Costs: Need re-application every 3-5 years, consider long-term economics

3️⃣ Seoul City Cool Roof Projects and Expansion Plans

✅ Seoul City's Step-by-Step Expansion Strategy

• Expansion is happening from public to private sectors. Main progress is as follows:

  • Started cool roof pilot projects focusing on public facilities like schools and welfare centers from 2019.
  • Installed cool roofs in about 200 public facilities by 2023 to verify effectiveness.
  • Expanded support projects to low-income and vulnerable households from 2024.
  • This year, expanded support scope to private homes starting with 20 households in Seongdong District.

• Expansion to apartment complexes and commercial facilities is also being pursued. Main plans are as follows:

  • Conducting demonstration projects in large apartment complexes to develop collective housing application models.
  • Reviewing joint investment methods with business owners for commercial facilities and factory buildings.
  • Also considering incentive systems that encourage cool roof installation in new buildings.
  • Long-term consideration of mandatory installation for buildings above certain sizes.

✅ Connection with Other Local Governments and Government Policies

• Nationwide expansion foundation is being established. Main trends are as follows:

  • Major cities like Busan, Daegu, and Gwangju are benchmarking Seoul City's model.
  • Ministry of Land, Infrastructure and Transport is conducting cool roof technology standardization as part of green building policy.
  • Ministry of Environment has included cool roofs in climate change adaptation policy and expanded budget support.
  • Research institutions like Korea Institute of Energy Technology are developing Korean-style cool roof technology.

• Economic incentives and support measures are being strengthened. Main plans are as follows:

  • Provide full construction cost support to vulnerable groups and 50-70% subsidies to general households.
  • Reviewing property tax or comprehensive real estate tax reduction benefits for cool roof installation.
  • Also pursuing plans to give additional points for energy efficiency grade certification.
  • Parallel support for technology development and standardization to foster related companies.

4️⃣ Related Term Explanations

🔎 Urban Heat Island Effect

• Urban heat island effect is when urban areas have higher temperatures than surrounding areas.
  • Urban heat island effect refers to a climate phenomenon where urban area temperatures are higher than surrounding rural or natural areas. It got the name 'heat island' because cities look like warm islands over the sea.
  • Main causes include: First, artificial structures like asphalt and concrete absorb and store lots of solar heat. Second, artificial heat from cars and air conditioners raises city temperatures. Third, reduced green spaces from urban development decreases natural cooling effects. Fourth, high-rise buildings block wind flow, preventing heat from escaping easily.
  • Urban heat island effects worsen summer heat waves and cause cooling energy consumption to surge. It also causes air quality deterioration and health problems, so mitigation technologies like cool roofs are receiving attention as important solutions. In Seoul's case, temperature differences between downtown and outskirt areas reach up to 7-8 degrees in summer.

🔎 Solar Reflectance

• Solar reflectance is an indicator showing how much sunlight a surface reflects.
  • Solar reflectance refers to the percentage of sunlight that is reflected back out of the total sunlight hitting a surface. It's shown as values between 0 and 1, where closer to 1 means higher reflection and cooler surfaces.
  • Looking at typical building materials' reflectance: First, black asphalt is very low at 0.05-0.15. Second, regular concrete is around 0.20-0.35 level. Third, white paint shows high reflectance at 0.70-0.90. Fourth, special reflective coating materials can achieve 0.85-0.95.
  • Cool roofs generally use materials with reflectance of 0.65 or higher. Higher reflectance lowers surface temperature for greater cooling effects. However, glare from reflected light and impacts on nearby buildings must also be considered.

🔎 Thermal Emittance

• Thermal emittance is a number showing how well a surface releases absorbed heat.
  • Thermal emittance refers to an indicator showing the ability of objects to re-emit absorbed heat energy in infrared form. It's shown as values between 0 and 1, where closer to 1 means materials that release heat well.
  • Cool roof performance is determined by both solar reflectance and thermal emittance. First, high reflectance minimizes solar heat absorption. Second, high emittance quickly releases unavoidably absorbed heat. Third, both numbers must be high to get optimal cool roof effects.
  • Most general building materials have thermal emittance of 0.85-0.95, which is quite high, so cool roofs mainly focus on improving reflectance. However, some metal materials have low emittance and need special coating treatment. Latest cool roof products use composite materials that optimize both reflectance and emittance.

5️⃣ Frequently Asked Questions (FAQ)

Q: How much does cool roof installation cost, and when can you recover the investment?

A: Generally 10,000-30,000 won per square meter, and investment recovery is possible within 3-7 years through cooling cost savings.

• Cool roof installation costs vary depending on building size and materials used. First, basic installation using reflective paint costs around 10,000-15,000 won per square meter. Second, using high-performance coating materials or membranes can cost up to 20,000-30,000 won per square meter. Third, for a 30-pyeong single house, costs are about 1-3 million won. Fourth, actual burden is greatly reduced by receiving 50-100% subsidies through local government support programs like Seoul City's.
• Investment recovery period is determined by cooling cost saving effects. A household with 500,000 won annual cooling costs saving 20% can save 100,000 won yearly, so with 1.5 million won installation costs, investment can be recovered in 15 years. However, considering electricity rate increases and increasing heat wave days, actual recovery is possible within 7-10 years.

Q: Don't cool roofs actually increase heating costs in winter?

A: Winter heating cost increases exist, but annually overall energy savings effects are still greater.

• Cool roofs reflect solar heat in winter too, so theoretically they can increase heating loads. First, on sunny winter days, reduced solar heat utilization effects can slightly raise heating costs. Second, however, Korea's summer cooling period is shorter than winter heating period, and cooling energy unit costs are much higher than heating. Third, actual research results show winter heating cost increases are only 20-30% of summer cooling cost savings, so annual totals still show energy cost saving effects.
• Also, the better a building's insulation performance, the smaller seasonal effect differences become, making cool roof net effects even greater. According to latest research, Seoul area can achieve 5-15% annual energy cost savings, and with climate change making summers longer, long-term savings effects are expected to be even greater.

Q: Can cool roofs be applied to all roofs? Are there limitations?

A: Applicable to most roofs, but roof materials, slope angles, and surrounding environments must be considered.

• Cool roofs can be applied to various roof types but have some considerations. First, effects are greatest on flat roofs or gently sloped roofs (slopes under 30 degrees). Steep roofs have limited effects due to small sunlight exposure areas. Second, asphalt, concrete, and metal roofs are all applicable, but suitable coatings differ by material. Third, roofs in poor condition may need repair work first.
• Environmental limitations also exist. First, roofs with much shade from surrounding high-rise buildings have reduced effects. Second, glare from reflected light can affect nearby buildings or roads, requiring advance review. Third, application may be difficult in cultural heritage sites or landscape districts due to color restrictions. Fourth, coastal or industrial areas must consider durability degradation from salt or pollutants.

Table of Contents

• Go to Guide