Cool roofs prevent solar heat from entering your building and help remove heat that is already in the building.

If you do not have air conditioning in your building, a cool roof can help lower the internal temperature by 1-3°C. This can help significantly improve comfort and health. If you were thinking about buying air conditioning, the improvements from a cool roof may convince you that you don’t need one!

If you already have air conditioning in your building, a cool roof can help reduce the amount of energy you use and lower your energy costs.

Cool roofs are most effective on 1-2 story buildings and buildings with large roofs. These kinds of buildings often absorb more solar energy through their roof than through their walls or windows.

Residences, schools, clinics, and community centers are often the right shape for a cool roof to be effective.

The cost of a cool roof will depend on the size of the roof and on the price of labor and logistics. A benchmark cost is about $5-15/m2 USD of roof area.

It is most cost-effective to install a cool roof as part of your normal maintenance program. Consider using a cool roof product that is also waterproof — this may save you the money you would otherwise spend on a separate waterproofing product.

On their own, cool roof coatings may cost about $3/m2 USD of roof area. This will depend on the size of the container and on the coverage rate of the paint, or how much roof area you can cover with 1 liter. Coverage rate will be different for each coating and will depend on what material the roof is made from — if the roof surface is concrete, the coverage rate may be 1 m2/L, but it may be a little higher if it is metal. Coverage rate will also depend on how many coats are needed to achieve a finished coating.

Contact product manufacturers and review any product data sheets for more information about cost and coverage rates for particular products.

The lifetime of a cool roof will depend on which product you choose and how well you maintain the cool roof after it is installed. Some products last three years, while others are more expensive and can last up to 20 years. The product manufacturer will be able to tell you about its expected durability and about how to properly maintain it.

The cooling performance of a cool roof will decrease over time. A product data sheet may indicate its initial performance and its performance after three years. Factors that reduce cool roof performance include dirt or vegetation covering the surface, degradation from exposure to ultraviolet light, and people walking on the roof, among others.

Cool roof coatings can be applied to most common roof materials including concrete, metal, fiber cement, and many others. Some roof materials will require only one coat of cool roof material, while some will require two. Some may require a primer coat using a different product. Make sure to find a product that is compatible with your roof, and contact the manufacturer directly for instructions or if you have any questions.

Make sure to follow safe practices when working on a roof.

Refer to manufacturer instructions for the particular product and roof material in your installation. Installing a cool roof does not require expensive specialty tools. You will likely need to clean the roof of any debris, repair and seal any cracks, and then install the primer or cool roof coating using a brush or other applicator tool. The manufacturer instructions will also tell you important details like the number of coats of product that are needed, what outdoor temperatures are acceptable to paint in, and how long to wait if it has rained recently.

Cool roof coatings may be available from suppliers of paints for residential, commercial, or industrial use. They are made by many manufacturers and may also be available through e-commerce websites.
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The Cool Roof Rating Council maintains a directory of cool roof products. Look through this to see if any brand names are familiar to you and sell products near you.

Make sure you find a product that is compatible with your roof surface material. Ask the product manufacturer if you have any questions.

It is important to consider things like performance, durability, cost, and ease of installation. Choose a product that offers the combination appropriate for your needs. If you want to use a cool roof product as a waterproofing layer, make sure you find a product that is certified for this purpose by the manufacturer.

Cool roof performance is usually characterized using measurements of solar reflectance (or reflectivity) and thermal emittance (or emissivity). A high performing cool roof will have a high solar reflectance (>70%) and high thermal emittance (>75%). Sometimes you might see these combined into one number, called the Solar Reflectance Index (SRI), where high performing cool roof will have a high SRI (>82).

Make sure to follow manufacturer instructions for the cool roof product you have chosen. Maintenance for a cool roof will be similar to maintenance for other roof coatings. You will need to keep it clean, check for and repair cracks, and install a new coat from time to time.

There are many effective and low-cost ways to keep your building cool. Cool roofs work well in combination with any of these approaches.

If your building is air conditioned, the most important thing you can do is make sure it is well insulated. Prioritize insulation on the underside of the roof (or the ceiling if you have an air cavity), then insulate the walls.

If your building is not air conditioned, install blinds or window covers on the building exterior to let people cover the windows when the sun is too hot. This change alone can reduce room temperatures by 10°C! Try to increase ventilation by opening windows or installing portals above windows or doors to allow air flow at the top of the building. If you live in a climate that is usually warm or hot, don't install insulation — this will trap heat inside the building and make it more uncomfortable. If you live in a climate that is sometimes cool or cold, insulation can help keep you warm in cold seasons but may make you less comfortable in hot seasons.

Yes, unless the climate is cool or cold all year. This is true for buildings whether or not they have mechanical heating and cooling.

In a cool or cold season, a building with a cool roof will be slightly cooler than a building without one, which may increase discomfort or require additional heating. This is called the "winter penalty". However, the benefits provided by a cool roof in warm or hot seasons outweigh the 'winter penalty'. This is because in cool or cold seasons, the sun is in the sky for less time and at lower angles, so it does not have as much of an effect on the temperature inside the building. Therefore, neither does the cool roof.

If a good quality cool roof product is compatible with the roof surface and is properly installed and maintained, it should not affect the quality of runoff from the roof.