Tag Archives: Cool Flat Roofing

Challenging Prior Misconceptions in the Roofing Industry

An Urban Legend Debunked

For quite a few years now, roofers have been using highly reflective low-slope roof membranes that are also known as “cool roofs.” Ever since their introduction in the 1990’s, this roofing system has been said to to spur moisture accumulation in low-slope roofs inhighly reflective roofing systemboth hot and cold climates. This belief has morphed into an urban legend of sorts that states that such cool roofs should be avoided because they will accumulate more moisture when compared with non reflective membranes. With this in mind, fears of facer failure, loss of R-value and biological growth follow. This so-called “fact” is currently being used in marketing and sales presentations for non reflective roofs as scientific fact, but when physics is used to assess moisture accumulation in highly reflective roofs, the widely spread urban legend can be largely discredited.

Moisture Accumulation Phenomenons

When trying to substantiate the concern about moisture build up, it is key to consider how moisture moves within a roof system. There are four major phenomenons to consider. First is vapor diffusion. Such diffusion occurs when a concentration gradient is present. More specifically, the catalyst of diffusion is a difference in water vapor pressure between two points, such as the inside and outside of a building. If you consider a hot and humid climate such as Arizona’s, you can conclude that the water vapor pressure outside the building is higher than it is inside. Water vapor in the air then will have a propensity to move from high-vapor pressure outside to lower pressure inside. The exact opposite is true in cold and dry outside climates. This same scenario occurs in the roofing system with water molecules wanting to move from a high-vapor pressure area to a low-pressure area. The next category of moisture movement is capillary movement. This phenomenon can be demonstrated through thinking about how a paper towel works. When you wipe up water with it, the water doesn’t jump into the towel but rather, capillary movement causes the absorption of the water into the towel. The more absorbent the towel, the greater the capillary action. This capillary action can occur in roofs within the microscopic pores within the material, the boards of high-density fiberglass, and in the tiny apiaries between singular glass fibers. Next on the list is gravity driven moisture movement. This occurs if there is a gap in the roofing system and precipitation enters. Gravity will cause the liquid to run down into the system and eventually into the building. The last form of moisture movement is mass transport by moving air. If there is natural or artificial air movement, there is the potential for mass transport. This is the most understated of the four moisture movement categories but they all can cause detrimental amount of moisture into a roof system.

Highly Reflective Versus Non Reflective Roofing Systems 

The Midwest Roofing Contractors Association in Manhattan conducted a test bed research project to test the temperature differential between two roofing systems. They were both constructed using the same insulation, attachment method, and solar exposure, and were cool roof roofing systemover shared airspace. The only difference stemmed from the membrane reflectivity– one being highly reflective (69%) and the other non reflective (7%). Several data findings emerged. First, the highly reflective roof, as is connotated by the term “cool roof,” operates at a lower temperate than the non reflective roof. Next, during nighttime hours, when incoming solar radiation is absent, the two systems have nearly identical temperatures. Lastly, when there is obvious nighttime radiative cooling, the two membranes cool to temperatures below those of the air that surrounds them.

The Moisture and Temperature Connection

Reviewing this data, it is clear to see that highly reflective roof membranes operate at lower temperatures than non reflective roof membranes. Next we must consider the four forms of moisture movement. Air movement, liquid transfer by gravity, and capillary movement aren’t at all contingent on temperature, as substantiated by scientific evidence. Therefore, the highly reflective membrane cannot cause more moisture movement through these phenomenons. However, when it comes to the diffusion of water vapor, temperature is definitely a factor. Higher membrane temperatures will lead to increased diffusion rates or put more simply, a hot roof will dry down faster than a cool one. If you refer back to the study, and you consider moisture to move freely through these roof systems, there is nothing impeding the vapor in the interior. The maximum influx of moisture by diffusion would therefore occur when their temperatures are at their lowest. It is during nighttime when this happens that these roof systems are in complete temperature uniformity.  Therefore, the reflection scale of the roof system would bear no effect on the amount of moisture retention. However, when dawn comes and solar radiation comes into play, their operating temperatures diverge. A non reflective roof will then operate at a higher temperature and consequently be able to dry faster than a highly reflective roof. It can then be inferred that if a highly reflective roof does not diffuse all the moisture from the night before, there is moisture accumulation.

The End of “Cool Roof” Systems?

In conclusion, this piece of writing is simply here to challenge previous misconceptions. It is true that moisture accumulation can be exacerbated if the highly reflective roofing system has slight moisture gain during the night that it cannot rid itself of during the day. cool roof highly reflective roof systemHowever, one must think this over and concur that the highly reflective membrane didn’t cause this, it was just. Roofers therefore shouldn’t downright avoid such systems, but rather utilize the design and installation principles necessary to facilitate a quality, long lasting roof system. The roofing industry professionals just need to remember that if moisture enters under the membrane by any mechanism, the “cool roof,” highly reflective roofing membrane will be at a disadvantage when trying to drive out the moisture as a result of lower vapor pressures developed.

See Which Roofing System is the Best for You Today!

If you are in the Puget Sound region of Washington State and are in need of roofing, decking, waterproofing, or skylight installation services contact Chase Construction North West, Inc. today. We provide services in King County and Pierce County, along with major cities such as Seattle, Tacoma, Puyallup, Federal Way, Renton, Auburn, Des Moines and all of the surrounding cities. Make sure to fill out our free estimate form or call us at 253-445-8950 today!

Chase Construction Strives For “Green” Operations

The Uncool Effects of Cool Roofing

Cool roofing may not be as “cool” as we think!

COOL ROOFING

 

Beginning in the 1980’s research on the benefits of cool roofs was conducted by the Department of Energy in hopes to find a way to save on energy costs and reduce our carbon footprint on the environment. The widely accepted belief that has developed from this research is that white roofs are the most environmentally friendly and energy efficient choice when it comes to roofing. This “cool roof” solution has become a quick and low cost solution in hopes to reduce carbon emission which is known to effect climate change. However, it has been said that cool roofs are not a “quick fix” to save on energy costs and that in certain climates they may actually increase energy consumption.

Due to the belief that reflective roofing is the easiest solution to lowering energy costs and reversing the effects of climate change, there has not been much consideration of geographic location . Although roofing professionals know that depending on geographic location and weather conditions there is a roofing system required for each roof.

Reflective, or what is known as “cool roofs” have been proven to reduce air conditioning costs during hot summer months, which in return provides home and building owners a great deal on energy savings. However, take into consideration colder, northern climates where people must spend more money heating a building rather than cooling them, the cool roof solution may not be a smart choice for them. In return, a reflective roof may actually increase carbon emissions due to increased energy consumption.

 

Effects of Cool Roofing in Cool Climates

Aside from inefficiency, reflecting roofing systems can have negative consequences in cool climates. The roof cover only concept regarding white reflective roofing implements only changing the color of the roof top from black to white. However, this concept ignores the components that are underneath the surface and how they are effected by the transition from black to white. One issue that can arise from cool roofs being installed in cooler climates is condensation. During the summer surfaces stay cooler, however when temperatures are colder the surface remains cooler for a longer period of time. In return it will fall below the dew point and remain there longer compared to darker membranes, which leads to condensation formation.

Condensation is one of the most potentially hazardous consequences of cool roofing. How does condensation occur? Warm air begins to rise toward the roof when temperatures outside drop. With no air or vapor retarder the warm air that rises makes contact with a surface that has dropped below the dew point and forms condensation.

 

CONDENSATION

 

 

 

 

 

 

 

Warning Signs

There are several signs that can reveal the presence of condensation. One way to tell is when you walk on top of the roof, if there is a crackling noise below your feet it is a dead give away that there is frozen moisture in your roofing system. You can come across this situation typically when a roofing system is insulated with a single layer opposed to multiple layers. When multiple layers of insulation are implemented in a roofing system, the joints end up staggered which in turn makes warm, moist air to reach the underside of the roof membrane. Therefore, using multiple layers to insulate your roof, although not foolproof, can help to decrease the level of moisture collecting beneath a roof membrane. Another issue that can arise from the use of a single layer of insulation is that moisture can free between the insulation joints, which causes it to expand as it begins to freeze and pushes the edges of insulation boards apart. Moisture will also lead to the insulation warping. Therefore, when frozen inflation experiences warmer temperatures, the frozen moisture will begin to drip inside the building.  Another unfortunate result of condensation is adhesion loss. When moisture accumulates and does not have the opportunity to dry, insulation facers can weaken, and therefore the membrane can detach from the insulation which causes reduced wind uplift resistance.

 

How to avoid condensation

When choosing  a roofing membrane color make sure you take into consideration the climate in which the roof will be installed. Typically in northern and colder climates, a dark membrane is used, where in warmer southern climates, a white more reflective membrane is used. However, if you are to implement a reflective membrane in a cooler climate, one way to try and avoid condensation is to use a continuos air or vapor retarder, as well as using the multi layer insulation method.

Recycle Building

Although reflective roofs are installed with good intentions, in hopes to reduced energy costs as well as our carbon footprint. Do not forget that these benefits are typically seen in warmer, southern climates. Therefore, if you are going to install reflective roofs in cooler climates make sure you implement certain design modifications to help reduce the presence of condensation, because when installed cautiously and correctly, cool roofs can perform quite well in cooler climates!

Chase NW Roofing is factory trained and certified with GAF, IKO, Versico and Custom-Bilt Metals to install almost every roofing application. We specialize in composition shingles, torchdown, single ply, metal roofing, wood shakes, slate and concrete tile. We have been providing quality re-roofs in the North West for over a decade. If you are planning to re-roof your house, need an inspection give us a call at 253-445-8950, or fill out our free estimate form!

Green Roofing Trends: GAF’s Solar Powered Roof Vents

Eco-Friendly Roofing Practices 

Green-building-RooferAs time moves forward and we witness the blow that society has given to our environment a sense of urgency is stirred for innovation and change in the building community. Many manufacturer’s have developed effective eco-friendly alternatives in their product lines that are part of the new “building green” trend. Among those who are making a huge push to encourage builders and contractors to go green is GAF Roofing. GAF is leading the pack with their green roofer’s program and contractor certifications. They have produced many cool and green products in their award winning line of roofing materials but one that stands out to me is their “Green Machine” solar powered attic vent. 

The Green Machine Attic Vent by GAF Roofing 

GAF Solar Powered Attic Vent

The Green Machine solar power attic vent is a great green roofing solution. A huge issue roofing contractors run into when they are re-roofing an older home is inadequate attic ventilation. Code requirements have changed in the last 20 years so its not uncommon to see very few vents on a large roof of an older home. GAF’s solar powered attic vent provides the following benefits and features: 

  • It works weather the sun is out or not so it provides 24 hour a day cooling.
  • It uses 80% less power than a standard power vent. 
  • It automatically switches between solar and house power when necessary. 
  • This unit is controlled by the thermostat providing additional savings. 
  • It comes with a 5 year limited warranty and a 2 year labor protection plus warranty (some restrictions apply).
  • It is easy to change out in case of warranty issue. 

Locate A Green Roofing Contractor

If you are interested in having Green Roofing attic vents installed on your home start by locating a GAF Master Elite roofing contractor in your area. A Master Elite contractor is a top certified roofer and is the best when it comes to quality and customer satisfaction. Simply go to www.gaf.com an then:

Type in your zip code as shown in the picture below: 

 

GAF-Green-Roofing

This will pull up a list of top level Master Elite roofing contractors in your area, you will see a screen that looks like the one below. All of the Master Elite contractors as are safe choice. You can also find a roofer here with a designated Green Roofer certification from GAF:

 

GAF Master Elite Contractor Profiles

This contractor profile shows pictures of completed work, independent customer reviews and special awards and designations. If you are looking for a contractor that is focused on green building and recycling you will be able to locate one by the “Certified Green Roofer” emblem as pictured below. 

 

GAF Certified Green Roofer

 

Chase Construction NW, Inc proudly recycles its asphalt roofing shingles and installs sustainable building products. If you are interested in re-roofing your home or commercial building with green products or cool products contact us today at 253-445-8950. We specialize in all types of roofing. Chase NW has been servicing the roofing needs of the Puget Sound for over a decade including: Seattle, Bellevue, Renton, Auburn, Puyallup, Fife, Federal Way, Tacoma, Olympia and the surrounding cities. 

Related Articles & Green Roofing Resources: 

From Roofs To Roads-Asphalt Shingle Recycling

Save Money & The Environment By Recycling Asphalt Shingles 

How Cool Roofing Products Save You Money

Cool & Green Roofing By Marcus Anthony

Cool Flat Roofing-This is a site you can find a wealth of information about cool and sustainable roofing, seriously. Connect with Leo B. on google + for more info.  

Solar Roofing Information Houston-By Bill Hubbell-Another godfather in the cool roofing world.