What Makes a Roof Energy Efficient?

Why would you want to make your property more energy efficient? Well it would benefit you by saving money on energy bills, creating less strain on HVAC systems, and minimizing your property’s environmental impact. Basically, for a roof to be energy efficient, it needs to do a good job of reflecting the hot air off your roof instead of absorbing it. When a roof absorbs heat, that warmth is radiated into the air inside the building, and pretty soon the entire interior has become much warmer. A roof that reflects the sunlight off and bounces the heat back out into the atmosphere will do a much better job of protecting the home or business from hot air. 

Some roof types that have good reflective qualities are white TPO, PVC and Elastomeric Coatings. Cool roofing is probably the most popular and most effective in terms of energy efficiency for commercial roofs. Residential shingle manufacturers also have cool roofs, but the nuts are very expensive and not yet worth the cost. Manufacturers rate the energy efficiency of the roofing material by what’s called SRI values. You will have a hard time finding SRI values on shingles unless they are part of a cool series line such as GAF’s cool series. A common misconception about shingle roofing is that the lighter the color of the shingle, the cooler the house will be and will result in heating and cooling cost savings. The way the cool shingles work is the granules are coated in a chemical that reflects the heat. The downside is that the coating wears off in time and you will eventually lose your reflectivity, which is where the cost vs savings comes into play. Another roofing material for this type of job is a metal roof. You might think that metal would not be a good choice to save heating and cooling costs because it gets so hot when it sits out in the sun, but that is exactly why it works. The surface of the metal that is exposed to the sun gets super hot because it is reflecting all of the light and heat. Underneath the metal, however, remains relatively cool because the heat has been reflected away. Most commercial buildings will have a metal roofing substrate, and the roofing company will install insulation on top of the metal with a single-ply membrane to ensure the best insulation possible. 

Reflective Roof Coating

A reflective roof coating is applied to roofs to help reflect more sunlight from the surface, reducing the amount of heat absorbed by the roof. Also known as cool roofing, these roof coatings are available for different types of surfaces, in a number of colors and thicknesses, and can make a huge difference when it comes to saving money on energy costs and usage. On top of that, they also aid in creating more comfortable indoor environments, and play a role in prolonging the lifespan of your roof and the roofing materials.

The point of cool roof coatings is to keep the home cool in two distinct ways. The first is by solar reflectivity, or the coating’s ability to reflect sunlight as soon as it hits your structure. Instead of absorbing the sunlight and heat like a traditional roof, a cool roof reflects the light and heat away from your home, keeping your home cooler in the process. The other way that cool roofing helps to keep your home cooler is through thermal emittance. These roof coatings are now made with special materials that increase your roof’s thermal emittance level, or your roof’s ability to radiate absorbed heat back into the atmosphere instead of down into your home. It’s this potent combination of high solar reflectance and thermal emittance that make these roof coatings so effective at keeping your home cool and your energy costs and usage down.

Ventilation Cooling 

Ventilation is the least expensive and most energy-efficient way to cool buildings. Ventilation works best when combined with methods to avoid heat buildup in your home. In some cases, natural ventilation will suffice for cooling, although it usually needs to be supplemented with spot ventilation.

Insulation

Insulation in your home provides resistance to heat flow and lowers your heating and cooling cost. Properly insulating your home not only reduces heating and cooling costs, but also improves comfort. 

To understand how insulation works it helps to understand heat flow, which involves three basic mechanisms: conduction, convection, and radiation. Conduction is the way heat moves through materials, such as when a spoon placed in a hot cup of coffee conducts heat through its handle to your hand. Convection is the way heat circulates through liquids and gases, and is why lighter, warmer air rises, and cooler, denser air sinks in your home. Radiant heat travels in a straight line and heats anything solid in its path that absorbs its energy. Most common insulation materials work by slowing conductive heat flow and to a lesser extent convective heat flow. Radiant barriers and reflective insulation systems work by reducing radiant heat gain. To be effective, the reflective surface must face an air space. 

Regardless of the mechanism, heat flows from warmer to cooler until there is no longer a temperature difference. In your home, during the winter, heat flows directly from all heated living spaces to adjacent unheated attics, garages, basements, and even to the outdoors. Heat flow can also move indirectly through interior ceilings, walls, and floors wherever there is a difference in temperature. During the cooling season, heat flows from the outdoors to the interior of a house. To maintain comfort, the heat lost in the winter must be replaced by your heating system and the heat gained in the summer must be removed by your cooling system. 

An insulating material’s resistance to conductive heat flow is measured or rated in terms of its thermal resistance or R-value. The higher the R-value, the greater the insulating effectiveness. The R-value depends on the type of insulation, its thickness, and its density. The R-value of some insulations depends on temperature, aging, and moisture accumulation. When calculating the R-value of a multilayered installation, you add the R-value of the individual layers. 

Installing more insulation in your home increases the R-value and the resistance to heat flow. In general, increased insulation thickness will proportionally increase the R-value. However, as the installed thickness increases for loose-fill insulation, the settled density of the product increases due to compression of the insulation under its own weight. Because of this compression, loose-fill insulation R-value does not change proportionately with thickness. To determine how much insulation you need for your climate, consult with your local roofing contractor during your free estimate.

Cool Roofs

A cool roof is one that has been designed to reflect sunlight and absorb less heat than a standard roof. Nearly any type of building can benefit from a cool roof, but must consider the climate and other factors that come with the building’s geographic location before deciding to install one. 

Just as wearing light-colored clothing can help keep you cool on a sunny day, cool roofing materials that are designed to reflect more sunlight and absorb less heat than a standard roof complete the same objective. Cool roofs can be made of highly reflective types of paint, a sheet covering, or highly reflective tiles, rubber or shingles. Standard or dark roofs can reach temperatures of 150 degrees F or more in the summer sun. A cool roof under the same conditions could stay more than 50 degrees F cooler and save energy and money by using less air conditioning. 

Beyond the commercial building itself, cool roofs can also benefit the environment, especially when many buildings in a community have them. Cool roofs can reduce local air temperatures, which is sometimes referred to as the urban heat island effect. Lower peak electricity demand, which can help prevent power outages. Reduce power plant emissions, including carbon dioxide, sulfur dioxide, nitrous oxides, and mercury, by reducing cooling energy use in buildings. 

There are many types of roofing systems available, but the surface exposed to the sun is the one that determines if a roof is cool or not. You can usually make a new or existing roof cool by selecting the appropriate surface or applying a roof coating. Cool roof coatings are usually white or special reflective pigments that reflect sunlight. Coatings are like very thick paints that can protect the roof surface from ultraviolet light and chemical damage, and some offer water protection and restorative features. Roof coating products are available for most roof types.  

What is the Most Energy Efficient Roofing Option?

Not only does being more energy efficient help the environment as a whole, but it also can help your pocket book each month. Energy costs, whether it be gas, electricity, or other forms, are at all time highs. Increasing your home’s energy efficiency can be a great help when trying to pay bills. One of the biggest influences on the energy efficiency of a home is the type of roof that it has installed over it. In North America during the summer time it can get really hot, therefore, that means if you are trying to keep that hot air out, you should consider installing a cool roof or cool roof coating. Any homeowner would know that trying to keep the hot air out of the home can be very expensive, simply by running the air conditioner to return the house to a comfortable temperature. When building a residential property or commercial property, picking the right material for your roofing project can make a big difference in your heating and cooling costs down the line.