How To Find The Perfect Cool Roof Option For Your Home

Lillian SteinBy Lillian SteinOct 5, 20170

If you live in a region where it gets very hot during the summer months, you should seriously consider installing or upgrading to a cool roof. A cool roof is environment friendly, prevents your home from becoming unbearably hot in summer and also saves energy and money. Besides lower energy bills, you will also save on maintenance due to reduced operation of cooling equipment. All these benefits come at a very small one-time cost and to top it all, it enhances the value of your property.

The Problem With Conventional Roofing​

The Problem With Conventional Roofing​

Heat from the sun comes to us mainly as infrared radiation. When a material is exposed to the sun, part of this energy is absorbed and the rest is reflected. The amount of heat absorbed or reflected depends on a property called reflectance. Materials with high reflectance reflect a large portion of the heat they receive from the sun and absorb very little heat.

A second property called thermal emittance decides how fast a material gives up absorbed heat. Materials with high thermal emittance lose heat quickly and hence remain cooler and cool down faster than materials with low emittance.

Conventional roofs are made from materials that have low reflectance, low thermal emittance or both. Although their thermal emittance is high, conventional asphalt roofs have poor reflectance and absorb too much heat. Conventional metal roofs, on the other hand, have good reflectance, but their low thermal emittance means that they can’t get rid of absorbed heat quickly and take time to cool down.

Cool roofs have high solar reflectance and thermal emittance. As a result, they absorb less heat and are able to lose heat quickly. A cool roof can be up to 60°F cooler than a conventional roof during a hot summer day. Your home will remain cooler, will be more comfortable and will need less air-conditioning.

A cool roof is, therefore, a win-win situation whichever way you look at it. If you are upgrading your existing conventional roof, the cool roof options that you have depends on the roof material, the slope of the roof and its condition.

Cool Roof Solutions For Low-Sloped Roofs

Cool Roof Solutions For Low-Sloped Roofs

As the name suggests, a low-sloped roof has a very small gradient that rises less than 2 inches per foot of horizontal distance. The slope is essentially for drainage and the roof is almost invisible from the street. You can upgrade a conventional low-sloped roof to a cool roof by using a surface coating or covering it with a single-ply membrane. A roof contractor or consultant will be able to advise you about the best option as it depends on the condition of your roof.

Coatings​

Coatings are like paint and can be applied to the roof surface. They can be used on a variety of roofing materials and contain additives that discourage the growth of algae and molds, improve durability, increase adhesion and allow dirt to be easily washed off during rains. Coatings are suitable if your roof is in good condition or needs only minor repairs.

Cool roof coatings are mainly of two types: cementitious and elastomeric. Elastomeric coatings contain polymers to increase adhesion and reduce brittleness. Cementitious coatings contain cement particles. Coatings with both polymers and cement particles are also available. Either way, their thermal emittance is 1.8 to 1.9 times and reflectance is about 1.65 times that of conventional roofing materials. Elastomeric coatings have waterproofing properties. Cementitious coatings will not make your roof waterproof.

Single-Ply Membranes

Single-ply membranes come in sheets and are either glued or mechanically fixed to the surface of an existing roof. The sheets are joined by glue, tapes or heat welding. They are suitable irrespective of the condition of the roof. This makes them a good option if your existing roof needs extensive repairs.

Cool Roof Solutions For Steep-Sloped Roofs

Cool Roof Solutions For Steep-Sloped Roofs

Steep-sloped roofs gain over 2 inches in height per foot of horizontal distance. These roofs are a significant part of the elevation of the building and the surface of the roof is usually visible from the street. Several cool roof options are available for steep roofs, but their solar reflectance tends to be lower than products meant for low-sloped roofs.

Asphalt shingles are the most common cool roof material used in steep-sloped roofs and have about 50% market share in many regions. Their initial investment is also significantly lower than other options. The reflectance of these products ranges from 25% to 65%.

Cool colored tiles contain pigments which increase the ability of the roof to reflect infrared radiation. It is usually possible to find a cool roof option that closely matches a particular conventional tile in appearance. The difference in cost between conventional and cool roof tiles are not very significant and they are usually more durable than conventional tiles. The reflectance depends on the color of the tile and ranges from 25% to 75%.

Cool colored metal shingles are also available and they are also based on pigments that increase solar reflectance of the material. Their solar reflectance ranges from 20% to 90% depending on the color.

Conclusion

Depending on the type of roof you have or the type of roof that you are planning to build, you have several cool roof options to choose from. If you are building a new home or if you are planning to upgrade your existing roof, seek the advice of a competent roofing contractor or consultant. Cool roofs have several benefits and may cost almost the same as conventional roofing materials. Any extra cost can be recovered in a couple of years and you will continue to enjoy its benefits for many years to come.

0 replies

Leave a Reply

Want to join the discussion?
Feel free to contribute!

Leave a Reply

Your email address will not be published. Required fields are marked *