Rooftop Alterations, Like Skylights and Roof Monitors, Can Drive Building Value and Performance

Rooftops are an immensely underutilized resource for optimizing building performance. Rooftop strategies can include painting the roof white or installing a solar reflective “cool roof” to reduce summer cooling loads; covering the roof with vegetation to improve insulation, reduce storm-water runoff and provide community spaces; and mounting solar photovoltaic or solar hot-water panels to reduce utility bills.

The multiple functions of rooftop monitors. RENDERING: FCGA Architects

The multiple functions of rooftop monitors. RENDERING: FCGA Architects

Adding daylighting and ventilation through skylights and roof monitors is a strategy with growing popularity and potential. Common sense might lead us to believe that penetrating the roof with skylights and monitors could compromise a building’s insulation and thermal performance. However, with the availability of advanced products, such as glazing, suspended film and high-performance sealants, well-designed and constructed rooftop penetrations can successfully lower energy costs and improve occupant comfort and health.

Rooftop prescriptions vary for every individual project, and a variety of factors must be considered before proceeding with construction. For example, rooftop penetrations will primarily only affect the floor directly beneath the rooftop, so single-story buildings or multistory buildings with a central atrium are ideal. When further determining which types of projects would benefit from roof penetrations, the design team must perform thorough climatic analysis, examine the existing infrastructure and occupancy conditions, and weigh all variables through cost balancing. Before diving deep into analysis, it’s important to understand different types of rooftop penetrations in this capacity and how their design and operational synergies can enhance the value and performance of a building.

Design Synergies

Traditional skylights, tubular skylights and roof monitors are the main types of rooftop daylighting/ventilation penetrations and should be considered individually because of their varying benefits. Traditional skylights offer natural daylight, which can improve the health and productivity of building occupants. Tubular skylights capture sunlight from a small, clear dome on the roof; pass the light through a highly reflective tube; and diffuse the light through a lens into the building. Because of their high efficacy and smaller penetration area, tubular skylights have better thermal performance and are more suitable for harsher climates than traditional skylights.

Roof monitors are vertical fenestrations built into raised structures atop the roof. If the monitors are operational, they contribute exponential building-performance enhancements beyond the other penetration types, including stack-effect ventilation. The figure above depicts the many functions of roof monitors: natural daylighting, ventilation, passive heating and cooling, glare reduction and structural support for rooftop solar-power systems.

As with skylights, roof monitors help disperse natural daylight more evenly and completely throughout a room than windows on the side of a building. When paired with thermal mass, such as concrete or water, vertical glazing on the roof helps capture heat from the sun to offset the building’s heating load.

Glare presents a big problem for worker productivity in buildings; careful design of roof monitors and ceiling systems can help distribute the light and reduce contrast glare. Finally, monitors can be topped with angled roofing that matches the optimal sun exposure angle for solar panels mounted atop.

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Attention Roof System Designers: Numerous Roof Components Work Together to Affect a Building

There has been a great deal of opinion expressed in the past 15 years related to the roof cover(s), or the top surface of a roof system, such as “it can save you energy” and “it will reduce urban heat islands”. These opinions consequently have resulted in standards and code revisions that have had an extraordinary effect on the roofing industry.

The building type should influence the type of roof system designed. Some spaces, like this steel plant, are unconditioned, so insulation in the roof system is not desired.

The building type should influence the type of roof system designed. Some spaces, like this steel plant, are unconditioned, so insulation in the roof system is not desired.

Let’s say it loud and clear, “A single component, does not a roof make!”. Roofs are systems, composed of numerous components that work and interact together to affect the building in question. Regardless of your concern or goal—energy performance, urban heat-island minimization, long-term service life (in my opinion, the essence of sustainability) or protection from the elements—the performance is the result of an assembled set of roof system components.

Roof System Components

Energy conservation is an often-discussed potential of roofs, but many seem to think it is the result of only the roof-cover color. I think not. Energy performance is the result of many factors, including but not limited to:

Building use: Is the building an office, school, hospital, warehouse, fabrication facility, etc.? Each type of building use places different requirements on the roof system.

Spatial use and function be low the roof deck: It is not uncommon in urban areas to have mechanical rooms or interstitial spaces below the roof—spaces that require little to no heating or cooling. These spaces are typically unconditioned and unoccupied and receive no material benefit from the roof system in regard to energy savings.

Roof-deck type: The type of roof deck—whether steel; cast-in-place, precast and post-tensioned concrete; gypsum; cementitious wood fiber; or (don’t kill the messenger) plywood, which is a West Coast anomaly—affects air and moisture transport toward the exterior, as well as the type of roof system.

Roof-to-wall transition(s): The transition of the roofing to walls often results in unresolved design issues, as well as cavities that allow moisture and vapor transport.

Meanwhile others, like this indoor pool, require extreme care in design and should include a vapor retarder and insulation.

Meanwhile others, like this indoor pool, require extreme care in design and
should include a vapor retarder and insulation.

Roof air and/or vapor barrier: Its integration into the wall air barrier is very important. Failure to tie the two together creates a breach in the barrier.

Substrate board: Steel roof decks often require a substrate board to support the air and vapor barrier membranes. The substrate board also can be the first layer of the roof system to provide wind-uplift resistance.

Insulation type: Each insulation type—whether polyisocyanurate, expanded polystyrene, extruded polystyrene, wood fiber, foam glass or mineral wool—has differing R-values, some of which drop with time. Many insulation types have differing facer options and densities.

The number of insulation layers: This is very important! A single layer of insulation results in a high level of energy loss; 7 percent is the industry standard. When installing multiple layers of insulation, the joints should be offset from layer to layer to avoid vapor movement and thermal shorts.

Sealing: Voids between rooftop penetrations, adjacent board and the roof-edge perimeters can create large avenues for heat loss.

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A Solar Installer Explains the Many Ways Roofing Contractors Can Be Involved in Solar Installations

The solar-power industry has changed dramatically in the past five years. Products and manufacturers have come and gone; tax incentives have become less attractive; and requirements for utilities to maintain a certain percentage of their energy portfolio from renewable sources are not enough to help the market in most places. Despite these negatives, unique financing mechanisms and the remarkable decrease in the cost of solar panels keep the industry booming. These ups and downs demonstrate why Matthew Bennett, vice president for design and engineering and founder of Dovetail Solar & Wind, Athens, Ohio, refers to the industry as the “solar coaster”.

Bennett’s business, which was established in 1995, installs solar on residential and commercial buildings. As such, he has worked with a number of roofing contractors over the years and sees synergies between the trades. Roofing asked Bennett how roofing contractors and solar installers can improve their relationship and achieve successful solar installations upon watertight roofs.

Roofing: When must you coordinate with roofing contractors?

Bennett: On almost every commercial roof where roof penetrations are required we’ll have a roofer come in and flash the penetrations and sometimes install a sleeve to get our conduit off the roof and into the building.commercial solar array

The other common reason for coordinating with a roofer is because the roof may be under warranty. Sometimes the warranty is held by the roof manufacturer, so we receive a list of roofers who can do the inspection. Usually there’s an inspection that needs to happen before and after the solar installation. We’re sometimes paying $1,000 to get inspections.

A lot of times we’re not fastening solar panels to flat commercial roofs; we’re installing what’s called a ballasted system where we may need to use an approved pad or put down an additional membrane to protect the roof from the pan that is holding ballast and keeping the array on the roof. Sometimes different roofing manufacturers are picky about what they allow on the roof and different kinds of roofs require different treatment, so it’s important to have a good roofing contractor available.

Roofing: When you hire contractors, what are you looking for?

Bennett: We’re looking for a roofing contractor that does quality work at a fair price because, I’ll be honest, we’ve been overcharged by roofers more than any other subcontractor. We take notes when we work with a roofing contractor: how easy they are to work with, how responsive they are to emails and phone calls, the quality of work and the price. We know roughly what to expect after being in business all these years. If we get a fair quote from a recommended contractor, we’ll often go with them without looking at other bids. We prefer to use a roofer who is familiar with the roof. A good relationship with the customer also is an important consideration.

Roofing: Are there situations in which you defer entirely to the roofing contractor?

Bennett: It’s a little unusual. We just put a system on a slate roof on a million-dollar home. The roof was very steep and we didn’t even want to get on the slate, so we hired the roofer to install the rails and solar panels. We did all the electrical work and procurement. We provided one of our crew leaders to be there the entire time to train the roofing crew and help them because they had no experience with solar. They knew how to get around on a slate roof and mount the solar flashing and they actually installed the whole array. They did it in not much more time than we would’ve done it. We were very impressed with them.

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A Review of Slate Roofs: Design and Installation Manual

The Fair St. Christian Church, Springfield, Ohio, features North Country Black, Vermont Unfading Green and Vermont Unfading Red.

The Fair St. Christian
Church, Springfield, Ohio,
features North Country Black, Vermont Unfading Green and Vermont Unfading Red.

Over the years, I have read every slate and sheet-metal book I have been able to get my hands on. The National Slate Association’s Slate Roofs: Design and Installation Manual, 2010 edition, is by far the most comprehensive and practically designed slate roofing book I have read. As a slate roofing contractor, I recognize the value of the information being put forth in this book. It is loaded with information, ranging from the basic characteristics of slate through some of the most complex installation details relating to slate roofing and affiliated sheet-metal details. The details are designed to match the intended life cycle of a slate roof, which should last a century or more with proper care.

Too often I see architectural details that are over- or under-designed. If they are over-designed, the result is likely a much higher price for the building owner. Also, over-designed roofs many times have the unintended consequence of failing prematurely. On paper, the detail looks like it will last a lifetime but experience shows some of these details just will not work in the field. Under-designed roofs just cannot stand up to the 100-year life cycle of a slate roof. The details the NSA brings forth in this publication have been time-tested and provide a standard way for designers to create a roof design that will stand the test of time.

I believe if this book can become the standard from which all slate roof installers, designers and building owners can work, then we will all win. When the details are correct the first time around, the building owner will end up with the best roof possible without a bloated budget caused by inefficient design; the designer does not end up with a strained relationship with the contractor and building owner because of poor design; and the contractor is able to correctly install a long-lasting slate roof and create another satisfied customer.

The 2010 NSA manual has become the main source of information for slate roofing for my roofing company.

The National Slate Association

Slate has long played a part in the architecture of the new world. It was first introduced to the U.S. as ballast for ships coming across the Atlantic in the 1600s. Slate roofs have been found by archeological excavations in Jamestown, Va., dating as early as 1625, according to Preservation Brief 29, “The Repair, Replacement, and Maintenance of Historic Slate Roofs,” from the National Park Service, Washington, D.C.

Nearly a decade after our nation’s independence, the first slate quarry opened in Peach Bottom Township, Pa. From 1785, slate roofing production grew rapidly and hit its all-time peak around 1914. There were active quarries in Maine, New York, Pennsylvania, Vermont and Virginia. In 1915, slate roofing began to slowly decline because WWI took many of the able-bodied men, leaving quarries short of workers.

In 1922, the Poultney, Vt.-based National Slate Association was formed to promote the use of slate in roofing and structural applications. Many of the first U.S. slate standards were set in a book by the organization called Slate Roofs. However, the association became inactive in the late 1920s because of a lack of cohesion.National Slate Association logo

In 2002, a historic meeting took place in Sarasota Springs, N.Y. A group of slate manufacturers, roofers, architects, consultants and other interested parties met and reorganized the National Slate Association and formed a three-member board of directors. Matt Millen, Millen Roofing, Milwaukee, became the first president of the association. Today, the board of directors
includes 15 diverse members who are determined to ensure slate will be used extensively around the country. The National Slate Association’s purpose is to promote excellence in slate roofing practices through the development and dissemination of technical information, standards and educational resources.

To ensure it meets its goals, the association has implemented hail testing for the purpose of knowing the thicknesses of slates needed in hail-prone areas and fire testing to certify slate as a fire-resistant material for insurance companies. It also released Slate Roofs: Design and Installation Manual, which won the Rosemont, Ill.-based National Roofing Contractors Association’s Gold Circle Award for outstanding service to the industry. (See “A Review of Slate Roofs: Design and Installation Manual, to learn more about the manual’s contents.)

The National Slate Association’s current board of directors includes President John Chan, The Durable Slate Co., New Orleans; Senior Vice President Robert Fulmer, Fulmer Consultants, Freeport, Maine; Vice President Dave Large, North Country Slate, Toronto; Vice President Brian Chalsma, The Roofing Co., Hampton, Va.; and Treasurer Pete Papay, Penn Big Bed Slate Co., Slatington, Pa. Jeff Levine, Levine and Co., Ardmore, Pa., is the immediate past president, and Julie Palmer, also of Levine and Co., is the office manager.

Board members are Dan Cornwell, CC&L Roofing, Portland, Ore.; Alan Buohl, GSM Roofing, Ephrata, Pa.; Glenn Downes, Garlock French, Minneapolis; Clay Heald, New England Slate, Poultney, Vt.; Matt Hicks, Evergreen Slate Co., Middle Granville, N.Y.; Brad Jones Sr., Buckingham Slate Co., Arvonia, Va.; Craig LeGere, Mid-America Slate and Stone, Chesterfield, Mo.; Matt Millen, Millen Roofing, Milwaukee; and Russ Watsky, Russell Watsky Inc., Ossining, N.Y.

The National Slate Association would like to invite any interested parties to join the association. Sign up online or email John Chan. Write P.O. Box 172, Poultney, VT 05764.

A Slate Roofer Shares Slate’s History in and Benefits for the Carolinas

Although slate had been used as ballast for ships crossing the Atlantic as early as the mid-1600s, its use was somewhat sparse in the Carolinas until after the great fire. With the Civil War in full bloom, a catastrophic fire broke out in Charleston in 1861, and the city was decimated. However, the Great Reconstruction Era (1865-77) brought shiploads of slate and bricks from North Wales. Welsh slate from the Penrhyn quarries and bricks and tiles from Flintshire and Chester made their way to nearby Liverpool, England, and ultimately to the historic Battery of Charleston.

Not to be outdone, the American quarries started to ship to the Carolinas also. New quarries opened up all along the New York and Vermont corridor, and, in the South, the Virginia Buckingham Co. started quarrying slate in 1867. Slate roofing was growing exponentially at this time, and the Carolinas were consuming it at a very rapid rate.

This dormer features Vermont Black installed in a German style.

This dormer features Vermont Black installed in a German style.

As a large port city, Charleston was able to acquire a wealth of different types of slate for its roofs: purple and gray slates from Penrhyn, Wales; Pennsylvania black slates; lustrous black Buckingham slates from Virginia; and greens, purples and reds from Vermont. Although it took more than a decade, Charleston was rebuilt in a grand manner with beautiful slate roofs as far as the eye could see.

Unfortunately, in 1989 Hurricane Hugo struck Charleston, causing nearly $6 billion in damage. The silver lining was many of these historic properties with slate roofs were 100 to 200 years old by 1989 and were in need of major restoration. From 1989-91, Charleston experienced a huge building boom with the insurance companies footing the bill for the restoration of the city. Tradespeople skilled in historic restoration were called in from all over the country and world. Among them were slate roofers hired to assess and restore the city’s slate roofs.

Learning Experience

Having only been a slate roofer for four years at the time, Charleston proved to be a great learning experience for me. Often working 12- to 15-hour days to keep up with the workload, I was able to personally observe various slating techniques from more than a century ago.

For example, still one of the most unique slate roofs I’ve encountered in my 20-plus years in slate roofing, was on a private residence on King Street. It had sustained minimal damage, and in the process of our repairs, we could see why. The entire slate roof was laid in a bed of mortar with wooden pegs where one usually finds nails. Needless to say, it was quite an adventure to restore it back to its prominence.

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Are You ‘PV Ready’?

Commercial rooftops are an attractive platform for the installation of solar photovoltaic (PV) electricity-producing systems. These low-slope roofs offer an economical and sustainable structural foundation for renewable solar energy. As an example, one of the largest roof-mounted PV systems in North Carolina has been online for several months at the Old Dominion Freight Line Inc. vault logistics facility in Thomasville. Almost 7,700 solar panels completely cover the warehouse’s 160,000-square-foot roof and produce enough power (1.8 megawatts) to offset more than 90 percent of the building’s annual energy costs.

Success stories like Old Dominion’s are becoming increasingly common in the sunny Carolinas. However, it is important to remember a roof’s function is, first and foremost, to protect the building’s contents and people from the elements. In this regard, roofing professionals need to anticipate the potential risks associated with the installation of a roof-mounted PV system (array). This sort of due diligence is particularly important when installing PV systems on existing warranted roofs.

A broad selection of membranes and thicknesses are available for consideration when a PV installation is planned. Photo courtesy of GAF, Wayne, N.J., and Protech Roofing Service, San Diego

A broad selection of membranes and thicknesses are available for consideration when a PV installation is planned. Photo courtesy of GAF, Wayne, N.J., and Protech Roofing Service, San Diego

To help in these industry efforts, members of Waltham, Mass.-based SPRI—the trade association that represents sheet membrane and component suppliers to the commercial roofing industry—have developed “PV Ready” roof assemblies and guidelines designed to provide maximum protection for the roof (and maintain its warranty coverage).

In September, SPRI’s technical committee and board of directors also approved and distributed to its members Technical Bulletin 1-13A, “Summary of SPRI Membrane Manufacturer Photovoltaic (PV) Ready Roof Systems and Services”. The bulletin contains general guidelines from SPRI related to “PV Ready” roof assemblies. This article goes into more depth about issues related to PV installations, particularly on existing warranted roofs.

Ask the Right Questions

The installation of a PV system on an existing warranted roof raises many important questions for the roofing professional and building owner. For example, will the roof accommodate the added weight of the PV array? Logistically speaking, before property owners decide on a solar-power system, they will need to determine whether their roofs are sturdy enough to support
the additional loads put on the existing roof structure by the solar array.

An average solar panel and support system typically add a minimum of 3 to 4 pounds per square foot to the existing roof. It is the responsibility of the roofing professional to ensure this additional weight does not exceed the load limits determined by the building’s designer.

From an economic (life-cycle-cost) point of view, it makes sense the service life of the existing roof membrane will come close to matching the projected service life of the PV system. If not, a complex and costly reroofing project may be required long before the solar panels need to be replaced. In general, the underlying roofing system must provide the same minimum investment horizon—generally at least 25 years—to realize the full potential of the rooftop PV system.

Most PV arrays require penetrating the roof membrane. Even non-rack-type systems may include electrical conduits, wiring and other components that may need to be flashed in a professional manner. It is essential the responsibility for this flashing work rests with the roofing contractor.

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Downtown Storm-water Management

Founded in 2002, Xero Flor America (XFA) is the official U.S. distributor of the Xero Flor Green Roof System. XFA has made its home in Durham, N.C., since 2006 when the company relocated its national headquarters from Lansing, Mich. In July 2012, it moved locally into renovated offices in The Republik Building, located at 211 Rigsbee Avenue in downtown Durham’s historic district.

Originally constructed in the 1940s for the Durham Insurance Service Co., The Republik Building is perhaps known to local history buffs as the home of WSSB radio. Robert Shaw West, chairman and CEO of The Republik, a local firm offering brand strategy and communication services, purchased the property from the city of Durham. He renovated the outmoded offices into a more contemporary, open and collaborative work environment in 2006. XFA decided to become more connected to the business community downtown and searched for offices in the historic district—ideally in a building where the company would have the opportunity to showcase its green roof system. West had space available on the second floor for XFA to lease.

Completed in February 2013, the 2,343-square-foot Xero Flor green roof atop The Republik Building is the first green roof installed on a building in Durham’s downtown historic district.

Completed in February 2013, the 2,343-square-foot Xero Flor green roof atop The Republik Building is the first green roof installed on a building in Durham’s downtown historic district.

“It was serendipity,” West says. “Xero Flor was looking for offices downtown, and we had space. Plus, we had to reroof our building last year. Since we needed a new roof, it was an ideal time to also consider adding a green roof, which supports our commitment to sustainability.”

Completed in February 2013, the 2,343-square-foot Xero Flor green roof atop The Republik Building is the first green roof installed on a building in Durham’s downtown historic district.

Going Green on the Roof

In addition to the standard building-permit process, putting a green roof on a historic building required additional review and approval.

According to Anne Kramer, urban designer with the Durham City-County Planning Department, except for certain minor items, such as repainting a previously painted surface, most changes to building exteriors within an official historic district require a Certificate of Appropriateness (COA). The Durham Historic Preservation Commission oversees the process locally.

The commission’s goal is to ensure preservation of the architectural character of the historic district’s buildings and, therefore, had to ensure adding a green roof to the building would not alter or disrupt the appearance of downtown Durham. Demonstrating a green roof would not be visible from the street level was especially important. With the COA from the preservation commission, XFA and The Republik had the green light for the green roof. But first Baker Roofing, Raleigh, N.C., installed the new structural roof.

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Five Ways Construction Professionals Can Protect Their Contractual Rights and Avoid Misunderstandings

If your company has recently been awarded a contract for construction work, congratulations! In finding the work and having your bid accepted, you’ve demonstrated your capability to efficiently furnish high-quality labor and materials. At this point, many contractors have no choice but to immediately proceed with reviewing the schedule, scope of work and specifications, as well as preparing to mobilize labor to meet time-related demands. With this flurry of activity, many contractors forget to reduce the agreements to writing, fail to sign written agreements, or—worse—sign contracts without reading all the terms and conditions. The following tips and information can help busy contractors prevent common pitfalls from occurring and offer guidance for those mired in contractual disputes.

1. Put everything in writing.

Most construction professionals would agree written contracts are essential for projects with new or relatively unknown clients, but many feel that long relationships with clients and mutual trust and respect eliminate the need for written contracts. In fact, some fear written agreements have the potential to offend other professionals with whom they have a positive past working relationship. However, written contracts are essential in today’s economic and legal climate and can be seen as a way to honor the mutual respect many feel toward past and repeat clients. The primary purpose of a contract is not necessarily to give one party an advantage over the other. Instead, the goal is for both parties to clearly delineate each party’s expectations from the other to avoid unwanted surprises. If both parties are aware of the duties, responsibilities, risks and rewards before the project commences, there will be less potential for disputes and misunderstandings than there will be without a written agreement.

2. Know that complying with licensing statutes is essential to preserving contract rights.

North Carolina and South Carolina, like most states, prohibit unlicensed contractors from enforcing the provisions of their contracts if a license was required for the contract in question. Additionally, North Carolina case law requires contractors to strictly comply with N.C. General Statutes Chapter 87, which contains specific provisions about the name in which contractors can lawfully hold a license. Failure to comply with the statutes will prevent contractors from enforcing the provisions of their construction contracts.

South Carolina has taken an even stricter approach. Pursuant to S.C. Code Ann. §40-11-370, it is unlawful to engage in construction under a name other than the exact name on the license issued to the contractor (if a license is required for the work), and an entity that does so may not bring an action in law or in equity to enforce the provisions of a contract. This means even a duly licensed contractor can be barred from any recovery for breach of contract, including lien and bond lawsuits, if the contractor’s name on a written contract is even slightly different from the contractor’s name on the contractor’s license. Although some states have case law adopting this principle, South Carolina appears to be the only state that has codified the rule. Therefore, it is imperative a contractor’s name on the contract is the exact same name as the name on any contracting license required for the work in question.

3. Assume no damage for delay clauses are enforceable.

Both North and South Carolina courts generally enforce “no damage for delay” clauses, which specify owners will not be liable for a general contractor’s damages arising from delay, disruption or interference—even if the owner is responsible. General contractors can enforce these provisions against subcontractors or suppliers, too. Often, the contract will provide that additional time—contingent on written approval by the owner, architect or general contractor—is the sole remedy for delay.

South Carolina courts have recognized some exceptions to these clauses’ enforceability, however. The South Carolina Supreme Court held in Williams Electric Co. v. Metric Constructors Inc. (1997) delay caused by fraud, misrepresentation or bad faith; delay caused by active interference; unreasonable delay giving rise to abandonment of the contract; or delay caused by gross negligence can give rise to recoverable damages.

Similarly, North Carolina courts have overlooked “no damage for delay” clauses and allowed parties to recover damages arising from delays that constitute abandonment of a contract; active interference with the contract; and delays resulting from fraud, bad faith or arbitrary action. Additionally, damages from delays not reasonably contemplated by the parties are recoverable.

Many delay provisions are accompanied by notice requirements, too. Most contracts that do allow parties to recover for delay related damages require the party claiming damages to give notice of the delay, or the source of the delay, as soon as they are aware of it. What constitutes notice and reasonable knowledge of the delay can be open to interpretation. Ambiguity is best avoided through specific provisions in the contract.

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Rooftop Equipment Mounting and Penetrations for Low-slope Standing-seam Metal Roofs

Standing-seam metal roofing offers a durable, sustainable alternative to other roof types and can provide maintenance-free service for five to 10 decades. Sadly, this exceptional lifespan often is sabotaged with the mounting of essential rooftop equipment and ancillary mechanicals.

Metal roofing can make use of special seam-clamping hardware that grips the standing seam without puncturing the membrane. Seam clamps have made metal roofing a preferred roof type for mounting photovoltaic solar arrays. PHOTO: Metal Roof Advisory Group Ltd.

Metal roofing can make use of special seam-clamping hardware that grips the standing seam without puncturing the membrane. Seam clamps have made metal roofing a preferred roof type for mounting photovoltaic solar arrays.

Regardless of the roof type involved, consultants generally agree that the best way to prevent roof-related problems is to clear the rooftop of everything possible and just let it function as a roof—not a mechanical equipment platform. However, such a perfect roof continues to elude us, as it becomes necessary or convenient to mount HVAC equipment, screens to hide it, piping to fuel it, scuttles to access it and walkways to service it. The list of rooftop mountings also may include plumbing vents, satellite dishes, lightning protection, snow retention systems, solar collectors, advertising signage and fall-protection systems to maintain all the foregoing. To help achieve relatively trouble-free roofs, this segment provides some basic understanding of the dos and don’ts in situations where rooftop equipment mounting is requisite.

Penetration-free Attachment

A good “first rule” about any rooftop mounting is to avoid penetrating the membrane whenever possible. While this may seem obvious, the tenet is often violated with standing-seam metal. The norm for attaching things seems to involve anchoring the item to the structure through the roof. When this happens, it not only threatens weather integrity, but can also violate the membrane’s thermal-cycling behavior by inadvertently pinning the panel to the structure. Such a point of attachment will fatigue and fail from forces of thermal expansion within a short time. Fortunately, scores of items and equipment can be securely mounted to metal rooftops without any penetration whatsoever, actually making metal roofing more user-friendly than other roof types.

In terms of mounting ancillaries, metal roofing can use special seam-clamping hardware that grips the standing seam without puncturing the membrane. Unlike many other types of roofing, metal is a rigid, high-tensile material. The seam area creates a beam-like structure that can provide convenient anchorage for walkways, solar arrays, condensing units and gas piping without harming the roof’s weathering characteristics. Mechanicals can be safely and cost-effectively secured to these seam clamps, leaving the roof membrane penetration free. Seam clamps can provide holding strength of up to several thousand pounds on some profiles and gauges, last the life of the roof and preserve thermal-cycling characteristics. Using seam clamps when possible for ancillary mounting will eliminate unwanted holes and other potential problems.

Seam clamps allow even cumbersome ancillary items to be attached to metal roofs without penetrating the rooftop. PHOTO: Metal Roof Advisory Group Ltd.

Seam clamps allow even cumbersome ancillary items to be attached to metal roofs without penetrating the rooftop.

Clamps should be made only of noncorrosive metals—typically, aluminum with stainless-steel mounting hardware. These metals are compatible with virtually anything found on a metal roof, except copper (with which there are dissimilar metallurgy issues). Dissimilar metals in electrolytic contact will induce galvanic corrosion of the less noble metal. In cases involving copper roofing, brass clamps should be used with stainless-steel hardware.

Seam clamps generally integrate with the profile and seam folding, and in some way “pinch” the seam material to anchor them in place. Preferred methods of doing this involve setscrews tightened against the seam causing a detent in the seam material that in turn creates a mechanical interlock of the setscrew, seam and clamp, providing the greatest holding strength and durability. Setscrews should have round, polished points to prevent galling metallic coatings, which can lead to corrosion. In like fashion, and regardless of the method of engagement, any clamp device should avoid any sharp points or nodes that could potentially pierce or gall metallic coatings of steel or cause fatigue and fracture points of other metals.

It also is important to remember that any loads introduced into the clamp will be transferred to the panels and their anchorage to the structure. Consequently, anchorage must be capable of withstanding the added load. The best practice is to utilize clamps that have been appropriately tested for material and seam-specific holding strength; be sure in-service load does not exceed that of the published holding strength, including factors of safety. The roof manufacturer should also be consulted with respect to approval of devices used.

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