Cool Roofs: An Economical and Environmentally Friendly Option!

San Diego cool roofing materials

Traditional roofing materials absorb heat and allow the higher temperatures to seep into the building or living space beneath. Cool roofs have been designed to absorb less heat by reflecting the sunlight away from the structure and back into the atmosphere. The process is becoming more popular in Southern California and can be accomplished through specially developed sheet coverings, or reflective paints, tiles and shingles. Virtually every type of building in warmer regions will benefit from this roofing technology.

How Cool Roofs Work

In much the same way that Southern California residents wear light colored clothing to keep cool on the hot summer days, cool roofing uses the principles of solar reflectance and thermal emittance to maintain lower roof temperatures.

Solar reflectance refers to how the lighter colors are able to reflect rather than absorb the hot sun rays during the day. Thermal emittance refers to the rate with which a roofing material can release heat back into the atmosphere. While standard dark roof temperatures can reach 150°F or more during the summer, cool roofing which reflects this heat can be a vital way to protect the inside building temperature, greatly reducing cooling costs.

Features of Cool Roofing

The presence of a cool roof provides many benefits to homeowners, building owners and occupants, including:

  • Reduced utility bills due to decreased need for central air conditioning
  • Improved comfort, stable temperatures in spaces without air conditioning
  • Extended exterior roof lifespan due to decreased temperature and less exposure to harmful sun rays


Collectively they can also benefit the surrounding community when many buildings have them. Reflective surfaces can:

  • Reduce overall air temperatures in dense areas (urban heat island effect)
  • Reduce peak electricity demand, which can prevent unexpected power outages
  • Reduce harmful emissions, including carbon dioxide, sulfur dioxide, nitrous oxide and mercury

Turn an existing structure into a cool roof

Even though there are many different combinations of roofing systems, the surface that is exposed to the most sun rays will regulate the overall temperature. Most new and existing structures can be made energy efficient through a number of different processes.

Cool roof coatings are white or specially colored pigments that reflect sunlight. Coatings are thick paint-like substances applied by spray or brush to most roof types and protect the surface from ultraviolet light and chemical damage. Some coatings also offer moisture protection and restorative properties.

Transforming existing roofs into cool roofs may include coating or recovering the surface with a waterproof and reflective material. If the existing roof is in need of serious repair, it may be retrofitted or completely replaced with reflective materials.

Single-ply membranes: prefabricated sheets rolled onto the roof and attached with mechanical fasteners, chemical adhesives, or weighted gravel or stone. Single-ply membranes can be made cool by reformulating or coating dark materials with a lighter, reflective coating.

Built-up roofs: base sheets with fabric reinforcement layers and typically a dark protective layer at the surface. Built-up roofs can be made cool by treating the surface layer:
Use light colored, reflective marble chips instead of dark gravel in asphalt
For mineral surface sheets, choose reflective mineral chips or a factory-applied reflective coating instead of dark sealants
Apply a cool coating over existing dark asphalt emulsion coating.

Modified bitumen sheet membranes: at least one layer of plastic or rubber composite sealed with mineral granules or smooth finish; may be used to surface built-up roofs 
and is called a hybrid roof. Modified bitumen sheet membranes can be cooled when a factory cool roof coating is applied.

Spray polyurethane foam roofs: reaction of two liquid chemicals that expands to create a solid surface and is applied to the roof. Foams must have a protective coating to avoid moisture and ultraviolet light damage. Polyurethane foam roofs are made cool when the reflective protective coating is applied.

Shingle roofs: overlapping or interlocking composites of fiberglass, wood, metals, asphalt, or polymers. Cool shingles contain reflective enzymes, standard shingles can be factory pre-coated with a reflective sealant. Manufacturers recommend against coating non-treated existing asphalt shingles.
Tile roofs: concrete, clay, or slate tiles that may be coated with custom colors or textures as well as waterproofing sealants. Tile roofs can be made cool by choosing light colors or applying a reflective coating.

Metal roofs: variety of natural or painted finishes and some granular coated roofing. Metal surfaces are highly reflective but low in thermal emissions. They can be made reflective by applying reflective coatings or choosing a light colored paint.

New homes can be constructed with cool roofing, often for little expense. Whether installing on new homes or when replacing existing worn roofs is not much higher than traditional roofing choices. In addition, cool roofing options have longer lifespans than their dark asphalt counterparts.

Climate is important because cool roofs are especially effective in warm, sunny temperatures. Existing Southern California homeowners should consider several factors to determine if the installation cost of cool roofing will be offset by the utility bill savings and any applicable rebates or incentives. For example, the amount of energy conserved will depend on the existing insulation and climate of the home, the type of roof and the efficiency of the HVAC units.

Cool roof options offer a way for individuals to reduce their carbon footprint by reducing the number of greenhouse gases released into the air. These environmentally friendly materials also save money on air-conditioning costs and improve air quality. When enough are installed or replaced on a local scale, they can also lower temperatures across whole urban communities. Cool roofing not only makes sense but it saves money and helps the environment.

roofing Specialists of San Diego_medium logoHot summers are great for recreational activities and trips to the beach, but they can really cause a spike in utility bills and energy usage. Warmer climates require homeowners to make some small adjustments to compensate for the higher temperatures without sacrificing comfort or style. Having the wrong type of roofing for the climate can be a major factor in high energy bills. There are some easy ways to combat the situation, and the most important one is the choice of hot climate roofing materials.

Slate Tile

Light and earthy tile colors are naturally reflective, durable and do not require much regular maintenance. However, they are also very heavy, delicate and relatively expensive compared to other options. Transportation and installation costs are high, even when local or salvaged materials are used. Being the best roofing for hot climates, slate tiles are especially popular in Mediterranean, Middle Eastern and Spanish architecture. Slate tile is also one of the most expensive hot climate roofing choices, especially in areas where slate is not a readily available natural resource.

Clay and Terracotta

Traditional structures were roofed with clay and other earthen materials, which are natural heat reflectors. Modern terracotta is one of the best roofing material for hot climates such as Southern California and can be treated with special paints that make them resemble expensive slate tiles or ancient terracotta styles. Such treatments also help with weatherproofing and increased reflectivity efforts. These heavy clay roofing styles require a solid structure and are often curved into an ‘S’ shaped mold that helps the pieces interlock across the roof, especially intricate architectural styles. Although often used on stucco and other homes throughout San Diego, the tiles are susceptible to snapping during cold, wet climates. Proper construction allows for space under the tiles for air and water to escape, avoiding this problem as well as keeping the roofing temperature cool.

Concrete Tile

Like the other stone roofing materials for hot climates mentioned, concrete tile is heavy and has a natural ability to reflect ultraviolet rays that tend to raise the roofing temperature and allow excess heat to pass through the roof into the structure below. Concrete tile is an economical middle ground with pricing generally falling somewhere between traditional asphalt shingles and more expensive slate or terra cotta. Concrete is especially inexpensive when large batches produced, making it an excellent choice for industrial areas and developing areas where mass public housing is being created at once.

Concrete tile is much more pliable and easy to work with than pourable concrete. It is also easier to color making this cool roofing a popular favorite for industrial areas throughout San Diego. Little treatment is needed to maintain this hot climate roofing material as the imporous composition does not allow moisture to penetrate the underlying structure. The baking process which binds the sand, cement and water allows concrete to withstand the harshest weather elements.

Rubber or Plastic Membrane

The inspiration behind synthetic rubber and thermoplastic roofing materials for hot climates is a relatively simple solution to an age old problem. Raincoats, car covers and umbrellas all have properties that both repel water and quickly whisk away any water droplets that are left behind. The synthetic rubber is actually ethylene propylene diene monomer, or EPDM. It has been used extensively in commercial and retail centers in Southern California because it is very durable and effective in reflecting sun rays, which makes it one of the best commercial roofing materials for hot climates.

Thermoplastic and EPDM materials are both pliable and essentially weatherproof, meaning they are a practical choice for practically any style roof. They are so reflective that very little ultraviolet energy is absorbed into the home or building. In many cases, these materials are used as a foundation layer for other types of energy efficient and cool roofing options. Because they are easily applied and the core materials are not expensive, the installation cost of these roofing materials for hot climates is fairly low in San Diego.

White Barrel ‘S’ Tile

These tiles are made from a concrete composite and are a low cost solution to maintain a low roofing temperature even in the warmest of climates. Molded into half barrel, ‘S’ shapes, these white tiles are made in a fashion that imitates terracotta patterns and designs. They are also installed in much the same as molded clay and terracotta roofing options and are able to reflect about 40% more ultraviolet rays than their terracotta and clay counterparts. They can be formed and installed within a few days and have excellent reflective qualities that make them excellent hot climate roofing options for residential and business use.

White Flat Tile

As with the white barrel ‘S’ tiles, slate and concrete tiles, white flat tile cool roofing can be colored to suit the owner. White flat tiles are lightweight compared to their stone and concrete counterparts but are just as effective in keeping roofing temperatures moderate in warm climates. They are generally constructed of ceramic, cement and elastomeric material composites. Since white flat tiles are able to reflect more than 75% of the ultraviolet rays from the sun, they are one of the best roofing materials for hot climates.

One minor drawback to the reflective white tile is that it requires regular cleaning as part of a maintenance program. The more porous stone and concrete options hide dirt and grime better than the smooth white tiles. The periodic cleaning cost is a small price to pay compared to the energy savings that can be discovered for homeowners as well as commercial development companies.

Want help making the best roofing materials choice for your home or business, we can help. Have Roofing Specialists of San Diego out to perform a free no obligation estimate and consultation for your upcoming roofing project.

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