Roofing Fasteners and How They Affect Insulation Thermal Performance


Roofing Fasteners and How They Affect Insulation Thermal Performance

Until now, there has been surprisingly little research into the overall thermal impact of the fasteners that penetrate roofing insulation. A recent study shows that even relatively conservative use of fasteners creates enough thermal bridging between the roof deck and the insulation to substantially reduce the overall thermal performance of the building envelope.

Guest blogger Eric K. Olson, P.E. explains his research (Olson, Saldanha, and Hsu, “Thermal Performance Evaluation of Roofing Details to Improve Thermal Efficiency and Condensation Resistance,” ASTM Roofing Research and Systems and Standards Development, Vol 8, STP 1590, ASTM International, November 2015)

Introduction

Thermal insulation in roofing systems plays a substantial role in the overall thermal performance of the building envelope.  Energy code requirements for the R-value of the roofing insulation are becoming ever more stringent, requiring increased insulation thickness. Mechanical fasteners are commonly used to secure the insulation and roofing membrane to the structural roof deck.

Each metal fastener creates a thermal bridge that reduces the effectiveness of the insulation.  For a single fastener, the impact would probably be negligible. A typical roof, though, may include thousands of fasteners. The effect of these myriad thermal bridges adds up. That is, the combined impact of the fasteners can substantially reduce thermal performance.

Considering the potential impact involved, there is surprisingly little information in the roofing industry regarding the overall thermal impact of fasteners on roofing insulation. To explore and help quantify these thermal impacts, some colleagues and I decided to perform and publish the results of three-dimensional computer heat flow models of fasteners and other roofing details that penetrate the roofing insulation (Olson, Saldanha, and Hsu, “Thermal Performance Evaluation of Roofing Details to Improve Thermal Efficiency and Condensation Resistance,” ASTM Roofing Research and Systems and Standards Development, Vol 8, STP 1590, ASTM International, November 2015).

EverGuard-thermal-bridging

Modeling and Analysis

We modeled a roofing system with 4 in. of polyisocyanurate insulation and 1/2 in. gypsum cover board with a nominal R-value of R-27.0, over steel deck, with the insulation fastened using steel plates and #14 roofing screws with a diameter of 0.214 in.

Modeling one fastener with plate penetrating a one sq. ft. area of insulation (e.g., sixteen fasteners per 4 ft. by 4 ft. insulation board), we found the following:

  1. Case 1: With the steel plate above the gypsum cover board, the fastener and plate drop the R-value from R-27.0 to R-19.2 (a 29% reduction in R-value).
  2. Case 2: Placing the plate beneath adhered gypsum cover board provides little improvement due to poor thermal resistance of the gypsum, raising the R-value from R-19.2 to R-19.5.

Swapping out the gypsum cover board with 1/2 in. high-density polyisocyanurate cover board raises the nominal R-value of the system from R-27.0 to R-29.0.  Repeating the above analysis, we found the following:

  1. Case 3: With the steel plate above the polyisocyanurate cover board, the fastener and plate drop the R-value from R-29.0 to R-21.2. This is a 27% reduction in R-value as compared to the nominal R-value using polyisocyanurate cover board.
  2. Case 4: Placing the plate beneath adhered high-density polyisocyanurate cover board raises the R-value from R-21.2 to R-23.8. This is a 9% improvement as compared to the case with the plate on top of the polyisocyanurate cover board, but still an 18% reduction as compared to the nominal R-value using polyisocyanurate cover board.

The above cases represent high rates of fastening (one per sq. ft.) that may be encountered at corners or perimeter zones.  In practice, field-of-roof zones require fewer fasteners and have greater area, and thus have a greater influence on thermal performance than corner and perimeter zones.  The figure below graphs the effective R-value versus the number of evenly spaced #12 fasteners and steel plates per 4 ft. x 4 ft. insulation board, using the conditions of Case 1 (fasteners through and plates above gypsum cover board) above.

Change in effective R-value Relative to Number of Fasteners for Case 1

Effective R Value

As can be seen above, the thermal bridging created by even light fastening rates can be significant.  A pattern of five fasteners per board, frequently seen in field areas of a roof, drops the effective R-value to R-24.  This is an 11% reduction in R-value.

Our work to date indicates that mechanically fastening roofing insulation substantially reduces the roof’s thermal performance as compared to a similar system without fasteners. More work remains to be done to quantify thermal bridging through roofing systems. The influence of fastener diameter, the use of less conductive fasteners (like stainless steel), and the use of polymer plates in reducing thermal bridging should be explored.

A better understanding of these thermally bridging elements will help identify options to help mitigate their effect. This, in turn, will help designers to better specify the thermal performance characteristics of their roofing systems. 

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Published at Mon, 19 Jun 2017 14:37:53 +0000


Commercial Roofers Employees Donate to Provide Starving Children with Meals for A Year


Commercial Roofers Employees Donate to Provide Starving Children with Meals for A Year

Food for Children

Founded in 1994, Convoy of Hope is a faith-based, nonprofit organization with a driving passion to feed the world through children’s feeding initiatives, community outreach and disaster response. Through its Children’s Feeding Initiative, Convoy of Hope promotes healthy children and communities that are free from poverty and hunger. The organization currently feeds nearly 150,000 children in the Philippines, El Salvador, Nicaragua, Honduras, Haiti, Kenya, Ethiopia, Guatemala, South Africa and Tanzania.

NRCA member Commercial Roofers, Las Vegas, has been actively supporting Children’s Feeding Initiative since 2012 and has donated more than $20,000 to the organization during this time.

Sixty-five Commercial Roofers employees are supporting the Children’s Feeding Initiative by electing to have weekly or monthly payroll deductions that go toward the cause.

In 2016 alone, Commercial Roofing collected $12,000 from its employees for the initiative.

Many of the children enrolled in the Children’s Feeding Initiative have their only meal of the day at school – a meal provided by Convoy of Hope and its partners like Commercial Roofing.

“For every $10 donated by Commercial Roofers employees, we are able to feed a child for a month,” says Eric Neubauer, corporate relations director for Convoy of Hope. “To date, these employees have provided nearly 100 children food for an entire year.”

Commercial Roofers donations have given the children access to clean water and education, as well.

“On a basic level, the mission of Convoy of Hope is to give hope to hurting people around the world, be it in disaster response, child feeding programs, women’s empowerment, agriculture training or other initiatives the organizations sponsors,” says Scott Howard, president of Commercial Roofers and chairman of the Convoy of Hope Foundation.

Howard states Commercial Roofers involvement with Convoy for Hope and its Children’s Feeding Initiative allows its employees to contribute to an organization that contributes 90 percent of its donations to the intended cause rather than corporate expenses.

“Our team members know they are providing food to more than 100 children each and every day,” Howard says.

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Published at Tue, 06 Jun 2017 18:34:34 +0000


STATEMENT: National Roofing Week Shines a Spotlight on Industry Professionalism, Generosity


STATEMENT: National Roofing Week Shines a Spotlight on Industry Professionalism, Generosity

A statement from Reid Ribble, CEO of NRCA

NRW 2017

Each year, National Roofing Week is a time for the roofing industry to shine a spotlight on the professionals who give so much of themselves to our great industry and the communities where they live and work.

On every structure, the roof is the first line of defense, protecting our families, homes and businesses from winds and storms. Despite this fact, roof systems are often ignored until they are severely damaged.

During National Roofing Week, the industry is encouraged to raise the public’s awareness about the importance of a roof system and how important it is for homeowners and business owners to make educated decisions when choosing a roofing professional.

Professional roofing contractors also display a great deal of generosity in their communities, with little or no fanfare. National Roofing Week is a time to call attention to the great charitable contributions of members of the roofing industry who donate time, money and resources in support of those in need.

It is my pleasure to wish all roofing professionals a Happy National Roofing Week.

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Published at Thu, 08 Jun 2017 16:07:29 +0000


The Roofing Industry Alliance for Progress Announces Partnership with Ronald McDonald House Charities


The Roofing Industry Alliance for Progress Announces Partnership with Ronald McDonald House Charities

RMHC

Partnership to provide roof system maintenance and repair to Ronald McDonald House locations nationwide.

The Roofing Industry Alliance for Progress has announced its formal partnership with Ronald McDonald House Charities (RMHC) to provide regular roof system inspections, repair and replacement for the 184 Ronald McDonald House locations in the U.S. The Alliance also will provide a monetary donation to RMHC Global to help fund program services and infrastructure.

RMHC helps families with sick children stay together and close to the medical care and resources their children need, when they need it most. The Roofing Industry Alliance for Progress will provide support to the Ronald McDonald House program that offers much more than a place to stay. The Houses provide meals and the support and resources families need when their child is hospitalized or being treated at a hospital far from home. The House program allows families to focus solely on their child’s health and treatment, while RMHC takes care of the family.

“This collaboration will ensure the families staying at Ronald McDonald Houses will have a comfortable place to stay while their children are receiving the critical care that they need,” says Bennett Judson, executive director of The Alliance.

This partnership is also a strategic fit with the Charity’s commitment to environmental sustainability and the work they have done to ensure effective management of their Houses.

One or more members of The Alliance or NRCA will be identified to partner with local RMHC Chapters to provide needed roof system services at each location. Roof system replacements will be managed as individual projects, and, if necessary, several roofing contractors and manufacturers may be asked to contribute.

The partnership between the two organizations became official April 2017 during The Alliance’s member meeting in Coronado, Calif.

With work already begun with Chicago and Philadelphia area locations, The Alliance is looking forward to providing this critical piece of support to the RMHC System nationwide.

To learn more about this partnership or to connect with local Ronald McDonald Houses, please contact Bennett Judson at (800) 323-9545, ext. 7513 or bjudson@roofingindustryalliance.net.

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Published at Mon, 26 Jun 2017 19:17:40 +0000